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    New, Theatre

    Non-Technical Pyrotechnics

    July 13, 2019

    I’m currently a pyrotechnician on a big outdoors summer musical.  I happily admit that a large portion of my job is sitting around reading a book with an occasional “Pyro, go!” to keep things interesting, but when problems do pop up, I deal with them.  A large number of my problems happen during my preshow and so I have time to figure out how I want to solve my problem and do so without comment.

    However, due to firing on cue, it’s really obvious when I have an unexpected problem and I don’t have the luxury of troubleshooting once I’ve missed my cue.  So occasionally something goes wrong and I panic a bit.  I’ve had an annoying intermittent problem lately and was chatting with some of the crew about it using “pyro terms”. About halfway through the conversation I realized it was likely that the crew had never had the opportunity to learn about this potentially dangerous facet of the show we were all working on.

    For those performers, crew, and curious audience members looking to add some knowledge to their toolbag I present “Non-Technical Pyrotechnics”.


    The Laws

    Fireworks are explosives and so the government likes to keep track of them.  The Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATFE) and Department of Transportation (DoT) both do some regulating on the federal level.  ATFE cares about storage and spells out magazine (where the fireworks are stored) requirements in its “Orange Book”.  Generally, magazines need to be kept clean, no metal is allowed in them, no smoking in magazines (ever!), and the area around the magazine should be mowed and/or leaves raked.

    The Department of Transportation cares about transportation and packing.  There are some tricks here, but if professional-grade fireworks are traveling on a public road after having been sold, those fireworks are regulated by the DoT.  In general, the fireworks should be traveling in labeled boxes on a truck with orange diamond-shaped placards on it and the driver of the vehicle should have a commercial license with a hazardous materials endorsement.

    Labeling required by the DoT- if you see one of these, fireworks are around!

    That’s what’s happening on the federal level.  Unfortunately, professional-grade fireworks laws vary on the state level: North Dakota has nearly no laws at all while California is heavily regulated (as of July 2019).

    States that fall more in the middle of the legislation spectrum tend to adopt a version of two of the National Fire Protection Association’s standards: NFPA 1123 and NFPA 1126.  NFPA 1123 focuses on big fireworks: the tilt-your-head-back, feel-the-thump-in-your-chest-as-your-dog-runs-from-the-room kind of fireworks.  NFPA 1126 looks after a multitude of smaller effects although a NFPA 160 focuses specifically on flame effects (a puff of flame is probably NFPA 1126, but a jet of flame (or more) is probably NFPA 160).

    NFPA 1123 and 1126 are about 30 pages, combined, and tend to be common-sense laws to supplement and enforce a pyrotechnician’s experience.  NFPA 1123 has a section on barge shows: the deck of the ship should be kept clear, shooters should wear life vests with lights on them, and shooters should have a place to shelter during the show: either a structure on the boat or a temporary shelter as long as it is up to a certain standard.  For pyrotechnicians who don’t do barge shows often, these laws will help guide them in making safe decisions for their crew.

    In states that have adopted NFPA 1123 and/or 1126, the pyrotechnicians should have a copy of these standards onsite.

    To mention a few things relevant to those who work near, but not with, pyro: don’t smoke near fireworks, pyro should either be supervised or locked up, and if someone doesn’t need to be near the fireworks, they shouldn’t be.

    Manufacturing Pyrotechnics

    Pyrotechnics are handmade.  There may be parts of an effect that are made using machines, but all pyrotechnics are hand-assembled.  That may seem odd in today’s mass-manufactured world, but it’s because a stray spark from a machine could be catastrophic.  Firework shells (those big balls of light in the sky) are usually made in China and imported, although shells made in Japan are known for their high quality.  Smaller professional pyrotechnic effects are often made in the United States to save on importing costs, while consumer-level effects (think firework stands/tents) import from China.

    The Operator

    The operator is the lead pyrotechnician on a shoot- the one who is most likely to come over and introduce themselves to the person who bought the show.  The operator is the most important person on a fireworks shoot as “The operator shall have primary responsibility for safety.” (NPFA 1123 8.1.3).  The operator is your friend, and you can think of them as the safety “veto button”.  Everyone (including the operator and the crew) want to have a fun, uneventful, show but in states that have adopted NFPA 1123 or 1126, it is the operator’s legal responsibility to stop the show if an unsafe situation exists.

    Operators usually have to be licensed in the state that they are shooting in.  Requirements vary here, but operators are usually over 21, must show proof that they have worked on a certain number of shows, and pass a written test.  In Missouri, potential operators must show proof that they’ve worked on three shows and take an open-book test; in California, potential operators must go through a multi-stage licensing process over a number of years involving five letters of recommendation, several tests, and a potential audit of a shooter’s log book.  So, you know, licensing requirements vary.

    The Site

    Pyrotechnicians are usually required to submit their shoot site map in advance to someone in order to obtain permits: the site map will show where the fireworks will be shot from, the fallout area, and where the spectators are expected to be (as well as a few other things).  The fallout area can be dangerous and, unfortunately, spectators enjoy trying to sneak into the uncrowded, open area, in order to watch the fireworks from a slightly closer spot.  It is the legal job of the pyrotechnicians to chase the uninitiated from the fallout area due to the possibility of them being hit by a falling effect/burning debris.

    A site map for a concert from 2018

    Setting up the Show

    Most fireworks shows are going to be set up in the same general way: a firing system will send a signal to a module (an interchangeable electronic component) which the pyrotechnician has wired (to install an electric system) product (any pyrotechnic effect) into.  The firing system may be wired or wireless: a wired system has cables physically connecting the different modules while a wireless system depends on the firing system transmitting its signals and the modules receiving them.  The transmitter/receiver part means that a strong signal is highly important for wireless systems, and it’s worth it to note here that the signal strength is reduced when there are large numbers of wireless signals around (e.g. cell phones in a stadium).

    A Cobra 18M Wireless Module- 18 cues can be wired into this module.
    A FireOne Wired Module- 32 cues can be wired into this module.

    Occasionally a show will be hand-fired, and so there will be no firing system or modules.  Instead, a couple pyrotechnicians will put on safety gear (eye protection, ear protection, head protection, pants, long sleeves, gloves) and hold something on fire (I’ve seen road flares, and a butane torch).  The pyrotechnician will light the end of the firework, brace themselves, and the firework will go off two to three seconds later.  Nothing quite gets a shooter’s adrenaline up like a hand-fire show!

    But most fireworks are fired electrically, and so the pyrotechnician must insert an intermediate piece to convert an electric pulse into a flame that can shoot a firework.  This intermediate piece is called an electronic match (e-match for short) and has a tiny resistor in the end of it that is deliberately overwhelmed, causing the resistor to fail and catch on fire.  This tiny flame, once fed, starts the chain reaction that ends with a giant ball of light in the sky.

    An E-match

    Most large fireworks need an e-match, although smaller pyro effects are built to already include this resistor.

    Of note with e-matches: these are sensitive to any form of electricity.  If lightning is in the area, everyone should stay away from everything that is already wired up, and on dry days, pyrotechnicians should be careful to discharge any built-up static periodically.

    The last step in setting up a show is tone testing: here the pyrotechnician turns on the firing system and uses it to check continuity: that every cue that is expected to have product in it, has something wired into it.  All the pyrotechnician can see is if there is a completed circuit or not; if the electricity passes into one wire and back down the other wire.  Technically the product is not checked.  After thousands of years of fireworks, however, the industry is pretty sure that a firework will go “boom” when a flame is set to it.  Of note is that if something goes wrong during tone testing, product may go off.  No one should be near the effects when they are being tested.

    A Cobra 18R2 Wireless Remote- the numbered circles will light up if continuity for a cue is found during tone testing.

    Running the Show

    There are a few variations here (hand-fire vs electric vs electronic shows), but the point is an effect is triggered, and (hopefully!) it goes off.

    It’s unusual for large shows to have a 100% success rate (everything is hand-made, hand-wired…).  A failure rate of under 5% is considered “good”.

    Post-Show

    NFPA 1123 mandates that pyrotechnicians wait at least 10 minutes after the last fireworks shell is fired before anyone approaches the shoot site: it is possible that a shell did not fire on command (due to whatever reason) but has been sitting in its mortar, smouldering, waiting (this is called a hangfire).  Shells have been known to go off 30 minutes after a show.

    After at least 10 minutes, the operator can approach the shoot site and start looking for shells that didn’t go off.  Respect your operator as they do their post-show: their job is to look down the barrel of a smoking gun and figure out if the gun is smoking because it just went off, or because it is about to go off.

    After the operator has cleared the site, others can come in and start breaking things down.

    Further Reading

    National Fire Protection Agency 1123 : “Code for Fireworks Display”

    National Fire Protection Agency 1126: “Standard for the Use of Pyrotechnics Before a Proximate Audience”

    National Fire Protection Agency 160: “Standard for the Use of Flame Effects Before an Audience”

    Bureau of Alcohol, Firearms, Tobacco, and Explosive’s “Orange Book”

    Pyrotechnic Innovation’s “Fireworks Training: Dud”

    Dictionary.com’s “Module”

    Dictionary.com’s “Wire”

    Film, Theatre

    Foam Snow Machines

    April 26, 2019

    One oddly vivid memory I have is from the end of the 2002 movie Big Fat Liar.  In the final chase sequence (spoilers!) Paul Giamatti is chasing Frankie Muniz and Amanda Bynes through the Universal Studios backlot, onto and off of various sets (must have been a busy day at the lot!).  One of the sets they drive a golf cart through is a winterscape, and so Christmas music naturally starts playing as the actors take a moment to appreciate the suddenly snowy (and snowing) landscape.

    For whatever reason, I can still imagine Frankie Muniz and Amanda Bynes looking around as snow momentarily sticks in their hair.

    So I’ve wanted to look at snow machines for a while.  And not real “skiing season starts tomorrow but we haven’t gotten any snow yet” machines, no, I’ve been curious about the “it’s absolutely roasting in here, but we need to film now if we want the Christmas special to be out in time” snow machines.  I finally had some time to sit down and start researching… although I certainly expected it to take longer.

    Foam Snow Machine History

    Around 1990 Francisco Guerra wanted a big finale for his magic act and so he decided that he would make it snow indoors in Florida.  Through a fairly simple technique Guerra accomplished his goal and, several years later, patented the design and started selling foam snow machines.  After a re-branding (and a new website), the matured company claims to be an industry standard in major theme parks, on movie sets, and in smaller novelty applications.

    Inside a Machine

    Snow foam machines are oddly simplistic beasts, and depend on a fan, a fluid pump, and a sock.

    First the snow fluid has to get from its reservoir to the main part of the machine: usually some sort of fluid pump accomplishes this, although some snow machine models apparently rely on the Venturi Effect.  The Venturi Effect is caused by changing pipe (or hose) diameters: if a fluid flows from a wider diameter tube to a narrow-diameter one, the fluid will speed up.  Think of it as walking in a questionable neighborhood: if the route you’re taking suddenly has you passing through a dark, narrow alley… you’re probably going to hurry up.

    And if someone sees you running through a dark alley and decides that if you’re running in a direction, then there’s probably a reason and they should start running with you, well, that’s the Venturi effect.  In this way, one fluid (person 1) can draw a second stream of fluid (person 2) into a main pipe.

    Once the fluid is in the pipe, it is deposited onto… a sock.  Or, generally, any semi-absorptive porous material.

    Finally comes the fan.  The fan is mounted inside a box, faced toward a plate with holes drilled into it.  In the center of the plate is about a 1” hole; it is to outside of this hole that the conical sock is mounted, wide end towards the hole.  Multiple holes are also drilled surrounding the center hole, their location vaguely related to how large the “snowflakes” will end up being.

    Consumer snow machines and professional snow machines operate on the same principles, however they may be constructed in various ways to save costs, create different volumes of snow, reduce noise, etc.

    When a Snow Machine is Operating

    The fluid pump pumps soapy water onto the sock, soaking it.  The fan blows air inside of the sock, creating bubbles on the outside of the sock.  When the bubbles are large enough, the second set of holes blows the bubbles off the sock and into the surrounding air.  Yeah, that’s all there is to a foam snow machine.

    For cleaning and maintenance: running warm water through every now and again seems to be just fine for most people.  If snow ever stops falling, the culprit is usually the fluid pump, which can often be disassembled and cleaned with warm water.  Before long-term storage, the snow machine should be cleaned thoroughly, as the snow fluid will likely turn into a gooey mess if left stagnant for too long.

    Snow Fluid

    There are two classes of snow fluid, depending on the application needs: consumer and professional. 

    Consumer fluid is used when working with a friendly audience: they care more about the fact that it is “snowing” at all, instead of what exactly the flecks of snow look like.  With some trial-and-error, a decent formula can be found for a specific application.  Fair warning: DIY snow fluid involves soap, which will likely make the ground under the snowfall slick.

    Professional fluid is used for realism and/or safety: if you want dancers to perform The Nutcracker onstage with intermittent snow, you want to make sure that the fluid formula is tuned so that the dancers won’t slip on slick spots.  For obvious reasons, formulas for professional snow fluid are a closely guarded secret, but contain about 98% water and 2% “other” components.  Working with a professional company is the best way to ensure that the snow will evaporate before it hits the ground- leaving no slick surface for anyone to clean up.

    Of note is that DIY snow fluid will void the manufacturer’s warranty on the snow machine, and possibly reduce the life of the machine.  The main reason for this seems to be that DIY snow fluid is heavier than professional fluid, and so the pump and fan have to work harder to get the fluid where it needs to go.  Additionally, professional fluid apparently contains something to lubricate the snow machine- lubrication that is not present in DIY formulas.  Without that lubrication, gunk builds up and starts degrading the fluid lines and burning out the pump.

    So when choosing to use professional snow fluid or a DIY home brew, make sure that you’re making an informed choice!

    Sources: Formula 1, Formula 2, Formula 3, Formula 4, Formula 5, Formula 6, Formula 7, Formula 8, Formula 9, Formula 10, Formula 11, Formula 12, Formula 13, Formula 14, Formula 15, Formula 16

    To quickly break down why these recipes use what they use:

    Isopropyl Alcohol- lighter than water and evaporates quickly.  More alcohol will likely make the snowflakes bigger and fluffier, although changing the type of soap used may also create bigger flakes.

    Soap- the heart of the bubbles.  The Mr. Bubbles brand is highly popular, although others called for any children’s bubble bath: children’s bubble bath focuses on large bubbles to play with, while bubble bath mixtures marketed to adults focus more on scent.  The difference between bubble bath and dish soap is harder to figure out.  My guess is that bubble bath is designed to be gentler than dish soap, and so forms softer, bubbles.  Dish soap is harsher (apparently harsh enough to remove the wax from a car!) and might form slightly stiffer bubbles.  Of the two, bubble bath is probably slightly better for the snow machine.

    Water- something needs to dilute the soap and alcohol so that it’s able to be pumped.  Distilled water is usually preferred over tap water due to all the minerals in tap water: those minerals are not great for the snow machine.

    Glycerin- helps keep bubbles together and create larger flakes.  May also lubricate the snow machine.

    Propylene Glycol- may be used to reduce the freezing temperature of the water, so that fake snow can still be made in cold weather.

    Further Reading

    Zigmont Magic/FX: “The Absolute Facts on Fake Snow Machines”

    Youtube: “How a Snow Machine Works”

    Youtube: “Smoke and Snow Machine Pump Maintenance”

    Patent: “Illusionary Snow Apparatus”

    Do It Yourself Christmas: “Build a ‘Fake’ Snow Machine?”

    Youtube: “How to Make a Homemade Foam Snow Machine”

    Land O Lights: “Inexpensive Snow Machine Fluid”

    Theatre Effects: “Making it Snow”

    Halloween Forum: “DJ Snow Machines- How do They Work?”

    Do It Yourself Christmas: “Snow Fluid Recipe Anyone?”

    Internet Movie Database: “Big Fat Liar”

    Reference: “Venturi Effect”

    New

    The Laws of Projects

    January 28, 2019

    In ‘celebration’ of my final semester (where every one of my classes has one or more projects), I thought I would look up Murphy’s Law as well as any other bitterly humorous law relating to projects.  Do keep in mind Stigler’s Law though: “No scientific discovery is named after its original creator”!

     

    Murphy’s Law: “Anything that can go wrong, will go wrong.”

    A classic.  Not, perhaps, quite true, but certainly true enough!

    There are multiple stories telling how this law came about: in one Murphy was a hapless engineer who could not do anything right, another version paints Murphy as a supervisor having to watch out for the constant mistakes of one of his junior engineers, and a third takes a look at Murphy’s entire team in which at least one member of the team was always making mistakes.  However it came about, Murphy’s Law resonates with everyone who has ever worked on a project!

     

    Parkinson’s Law: “Work expands to fill the time available for its completion.”

    Lubarsky’s Law of Cybernetic Entomology: “There’s always one more bug.”

    I see these two as going hand-in-hand: when working on projects, one usually doesn’t try to stretch out the process and fill the time allotted, something just pops up and happens to take that time.  But when a hard deadline is reached and the project still has a few small wrinkles, the majority won’t notice and the project will be labeled a success.

    To myself and the other perfectionists out there: there’s always one more bug, and there will always continue to be one more bug.  Take a moment at the beginning of the project to determine the amount of time you are willing to commit, and then don’t move those goalposts.  There will always be another bug, always more time that can be sunk into a project.  Instead take a breath and move on.

     

    Finagle’s Third Law: “In any collection of data, the figure most obviously correct, beyond all need of checking, is the mistake.”

    I can vividly imagine this happening for a particular large report due at the end of the semester.  This is a bit of a “we’re all idiots at the end of the day” rule: just take a moment to doubt yourself, check yourself, and fix yourself, so that you can still look like a genius in the morning.

     

    The Queue Principle: “The longer you wait in line, the greater the likelihood that you are in the wrong line.”

    Whoever came up with this one was probably thinking about lines at grocery stores or the mall, but I find this principle interesting in terms of my school’s career fair.  Our career fair is extremely large, some two or three hundred companies, and the large companies (Google, Boeing, etc) have lines that can be over an hour long, while the naval recruiter can’t get anyone to make eye contact with him.  But… I had a friend who was cold-called by Google when they wanted to recruit him to a specialized team.  My classmates standing in line might get some cool swag, but it’s highly likely that they’re in the wrong line, since they currently have very little to distinguish themselves from the people in front and behind them.

     

    Vierodt’s Law: “Short intervals of time tend to be overestimated, and long intervals of time tend to be underestimated.”

    Golub’s Fourth Law of Computerdom: “Project teams detest weekly progress reporting because it so vividly manifests their lack of progress.”

    I came across something similar to Vierodt’s Law a few days ago, and this is one that I hope to live by this semester (and beyond, but thinking too far out is scary!).  Sure, I didn’t finish my to-do list for today, but by the end of the week I’ll have accomplished the few things I missed today, plus a bunch of other things I have yet to start.  Then in a few months I’ll graduate with a bachelor’s degree: a project I’ve been working on for several years now.  We can all agree that it’s ludicrous to put “bachelor’s degree” on a daily to-do list, but by spending years working towards a goal, we can accomplish something much larger than the effort put forth on any particular day.

    I suspect the second quote is going to be more immediately applicable, as I have weekly check-ins in at least one class.  A week still falls in Vierodt’s “short intervals”, and so people overestimate what they can get done and are frustrated when they can’t cram a month’s worth of work into one week.  But a long-term project is not a week, or even a month: a long-term project is several months or several years and the project will be the sum of each week’s work, not the average.

     

    So there are a few laws which I feel provide insight into the semester I have before me, and I hope you also find some of these helpful for school, work, or personal projects.

    Further Reading:

    A personal collection of humorous laws

    Wikipedia’s “List of Eponymous Laws”

    Another personal collection of humorous laws

    Misc

    Thor’s Hammer and Electromagnetism

    November 18, 2018

    A few years ago I had the opportunity to go on a backstage tour of Disneyland with my trade school.  We had an awesome weekend poking around backstage and learning about how permanent shows differ from the temporary shows we were used to, then, upon learning that we had a few Marvel nuts in our group, our tour guide got us a private Thor experience when the company was promoting the recent release of Thor: The Dark World.

    I wasn’t super-into Marvel then, but I enjoyed how excited my friends were, surprised by how detailed the meet-and-greet room was, and tickled by a nice moment when Thor asked a member of our group if they would like to try to lift his hammer and, if so, ascend the throne of Asguard.  To no one’s surprise, only the worthy Thor was able to wield the magical weapon and our party exited the experience with no new royalty among us.

    A short time later our guide re-joined us and began talking about the technical aspects of the Thor experience: included in that talk was a mention of the unmovable hammer, which a few of us had already (correctly) guessed was an electromagnet.

    Electromagnets are pretty neat: send an electric current through a wire, magic occurs, and you suddenly have a magnet.  Turn off the current and the magnet reverts back to simply a funky-looking device which is only vaguely magnetic.

     

    A Brief Review of Magnets

    Delving into research for this topic, I determined that magnets get really complicated really quickly.  On a high level, a permanent magnet has a north and a south pole: the north pole is attracted to south poles, the south pole is attracted to north poles, and both poles will reject a second pole oriented in the same direction (north rejects north, south rejects south).  These north and south poles are in turn caused by the orientation of groups of atoms called domains.  Each domain has about 1015 atoms.

    Think of a domain as an arrow: a permanent magnet has the arrows pointing in the same direction, while the chunks of metal used in electromagnets have their domains randomly oriented, with arrows pointing all over the place.  The beauty of the electromagnet is that the electrical current roughly sorts through the arrows (like on would sort a messy deck of cards or a pile of papers) and encourages them to orient themselves in the same direction.

    A layer deeper is where physics and quantum mechanics comes into play.

     

    The Physics of Electricity and Magnetism

    No one’s really sure how an individual atom is magnetic.  The best guess is that a magnetic atom has some lonely electrons in a particular location, leading to some lopsided geometry on the atomic level.  Electrons not only whiz around an atom, they spin around their own center while doing so (like the Earth spins on its own axis as it revolves around the sun!).  Electrons can have a spin of UP or DOWN, and will only pair up in its electron shell with an electron of the opposite spin direction: it’s possible that these spin directions (along with some geometry requirements) lead to an individual atom becoming a monopole- having a north or south pole, but not both.

    However, monopoles have not been proven to actually exist.  If you cut a permanent magnet in half, it will still have a north and south pole.  Cut it in half again, same thing.  If you continue cutting the magnet, you will continue to find a north and south pole up to and until the magnet is so small that it cannot be measured.  In talking to my physics professor about magnets, he told me that if I was able to prove the existence of magnetic monopoles, I would probably receive a Nobel prize and that I should use the money to buy him a Tesla Model S (but don’t worry, he would pay for the charging station himself).

    Putting the magnets aside for a moment and jumping to the somewhat lighter topic of electricity…

    An electric current flowing through a wire creates a magnetic field.  And now the physics gets ugly.

    Imagine a top view of two lines of evenly-spaced runners going past each other in opposite directions and at the same speed.  Now place yourself in the body of one runner.  Now (because running is a lot of work), imagine that your body (and line of runners) is still and the world is moving around you at the same speed that you were running.  From this perspective, it looks like the opposite line of runners is running really fast and you feel a slight attraction to those runners, because you too would like to be able to run really fast.

    Obviously, this is a simplification, but I find it far easier to think about than special relativity, the Lorenz invariance, and any sort of mathematical formulas in general.

    This attraction is an electrical attraction, which, because we don’t want to have to think about complicated things, is called a magnetic field.  In summary, an electrical current runs along a wire and creates a magnetic field at a right angle to itself as the individual charges swoon towards a second line of runners.

    So, like I said, magnets are complicated.

     

    Electromagnets are generally made of a metal (often iron) core tightly wrapped with a wire.  The more coils, the stronger the magnetic field that the wire produces, the quicker the domains in the iron core are aligned, and the stronger the electromagnet.  There is a fairly obvious upper limit here, though: once all the domains are aligned, the electromagnet is at its maximum strength.  To get a stronger electromagnet, one can increase the size of the core (more domains to align and more coils of wire) or increase the current in the wire (creating a stronger magnetic field).  Super electromagnets can be created by sending a ton of current through the wire, while cooling the system to make sure nothing catches on fire.

     

    A super electromagnet isn’t something that was used as a neat trick in a meet-and-greet though; a 3” electromagnet can be bought for less than $300 with a strength of over 1,000 pounds.  By putting an electromagnet in the floor and a strong permanent magnet in the top of Thor’s hammer, the actor and crew can easily make a moment of Asgardian magic using the mysterious principles of electromagnetism.

     

     

    Further Reading:

    CoolMagnetMan’s “Magnet Basics”

    StackEchange’s “How Do Moving Charges Produce Magnetic Fields?”

    Wikipedia’s “Magnetic Monopoles”

    Quora’s “Why Does a Moving Charge Produce a Magnetic Field Around It?”

    Quora’s “How Does an Electric Current Generate a Magnetic Field?”

    UCSB’s Science Line “Electric Current Producing Magnetic Effects”

    Theatre

    Stage Revolves

    October 6, 2018

    Several years ago, I had the opportunity to attend a short lecture on turntables, which spawned the basis of this article.  I just spent some time doing additional research, and now I hope to create a guide for those first learning about theatrical revolves.

     

    Types of Revolves

    In general, there are two types of revolves: the classic circle and everything else.  Once one thinks outside of a static circle revolve, there can be odd-shaped revolves, revolves within revolves, revolves mounted on elevators that lift up to reveal a scene below, or revolves that can move on and off stage on a giant wagon.

    Using a few basic principles, the simple circle revolve can be scaled either up or down, can be driven in different ways to account for different budgets, and even has the possibility to be staged near other revolves for a true DJ-desk type of staging experience.

     

    Mounting the Castors

    On a normal wagon rolling onstage and offstage, the wheels are mounted to the wagon, and every uneven dip in the stage floor affects the motion of that wagon.  This unevenness reduces the efficiency of the wagon, and forces whatever is moving the wagon (stage crew, a motor…) to work harder than they need to.

    As a turntable is, essentially, stationary, any resistance to its motion will be felt every time the turntable is revolved.  To reduce unnecessary work, castors are mounted to the stage floor (wheels pointing up) and shimmed, so that the revolve is perfectly level and unnecessary work is minimized.  However, because the castors are pointing up, they require a smooth contact surface to roll on: a smooth turntable requires a smooth underside.

     

    Turning the Revolve

    Once decked, there are two general ways to turn any revolve: either use crew/actors to push the revolve or use a motor to turn the revolve.  Of these, using a motor requires less labor (and looks more ‘magical’, but is costlier and can be noisier.

    There are three ways to use a motor for a turntable: attach the motor to a tire and use friction to drive the revolve, wrap a chain around the entire turntable and have the motor advance the chain (belt-driven), or mount the motor under the turntable and use a wheel on a track to drive the revolve (center-driven).

    Friction-driven revolves are most popular for those with a lower budget, as there is a maximum amount of power with least amount of fuss, however, a second (visible) tire is often added on top of the turntable to ensure proper contact with the turning tire.  With the stage slightly cluttered with mechanics or masking to hide the second tire, a friction-driven revolve will not give the cleanest look.

    Chain-driven revolves provide a cleaner look, but with an increase in cost and complexity; this revolve can be built into a deck, as no mechanics are required on top of the revolve.  This type of revolve requires a channel for the chain around the circumference of the disk, and likely some sort of increased friction in that channel to encourage the chain from slipping.  Near the motor is a series of pulleys and a winch to put tension in the chain: the more tension in the chain, the less likely the chain is to slip, but the more the chain may damage the channel it’s wrapped around.

    Center-driven revolves are what those with the largest budgets usually use: the motor is underneath the turntable, so the revolve can be built into a deck, and it requires no fussing with a chain.  On the downside, the motor is now in a difficult place to maintenance, and a beefier motor is required due to the closer proximity to the pivot point.

    Center-driven revolves also allow for more flexibility: want a turntable within a revolving ring?  The center turntable is center-driven.  An oval? Center-drive.  A turntable on an elevator?  Center-drive.

     

     

    Further Reading:

    Ben Teague’s “How to Build a Revolve or Turntable: An Illustrated Guide”

    Wikipedia’s “Revolving Stage”

    Stage Direction’s “Revolving in a Straight Line”

    The Guardian’s “A 360-Degree History of the Theater Revolve”

     

    Videos:

    Jigao Willie Wu’s “Hamilton Turntable Model”

    Jetijs’s “Rotating Platform”

    ImagineNation2’s “SceneAround Theatre System”

    Dean Montgomery’s “Rotating Stage for Community Theatre”

    Theatre

    Theatrical Fog, Smoke, and Haze

    September 22, 2018

    Fog.  Smoke.  Haze.  All words for the same thing, right?  Well, no.

    Smoke is rarely used to create any sort of visual effect in the theater: the particles in smoke are just not healthy for anyone to breathe in over an extended period.  Smoke is defined as solid particulates in the air, created by the process of combustion (i.e. burning something).  Combustion is a messy process, potentially releasing all sorts of toxic gases, and carries with it the risk of a flame near an audience.

    Haze is small liquid particles in the air which linger for long periods of time.  Haze is used to create a general “smoky” effect: the smoke that fills the kitchen when an inexperienced cook makes bacon, or the water particles in the air that show off beams of sunlight.  Because theatrical haze is engineered to linger, it’s hard to clear from the air when a scene changes.

    Fog is larger liquid particles in the air, which dissipate at varying rates of time.  Fog is the liquid/gas coming off a witch’s cauldron, the creeping mist in all movie cemeteries, and the swirling cloud of smoke when sugar drips into the bottom of a hot oven.  There are multiple types of fog- some that hug the ground, others that rise into the air- but the defining features of fog is that it’s (generally) safe to be around for long periods of time, and that it must be continually renewed, or it will dissipate.

     

    Fog is used more commonly, in places from theaters to front yards on Halloween, and is made in two ways: either by cooling a liquid, or by heating it up.

    For cryogenic fog, like fog made with dry ice, water is first heated and then rapidly cooled when a block of dry ice is dropped into the water.  The dry ice almost immediately expands and turns into a gas: this expansion agitates the water and breaks part of it into tiny water droplets, throwing them into the air.  This fog tends to stay close the ground as it starts off cold and becomes less visible as it heats up and rises.

    Cryogenic fog tends to be used for either small projects, science fairs or the occasional Halloween party, or for very large projects with 55-gallon drums of hot water.  When using low-lying fogs, one must remember that it will settle at the lowest point available: a dip in the ground, or perhaps the orchestra pit.  As any particulates in the air are not exactly great for humans over long exposure periods, care should be taken to restrain the fog with a simple well-decorated barrier.

    Smaller fog machines available to consumers from party stores work on a different principle: instead of cooling a liquid, ‘fog juice’ is essentially dissolved into warm air.

    An easy way to think of this is with a simple experiment: dissolving sugar into water.  At room temperature, a certain amount of sugar can dissolve into a set amount of water before the water becomes “saturated” and will not dissolve any more sugar: sugar that is added to a saturated solution will fall to the bottom of the container and remain there.  If the water is heated more sugar can be dissolved in it, creating a “supersaturated” solution.  As the supersaturated sugar/water mixture cools, some sugar will slowly re-form on the bottom of the glass (or on a string, if one is inserted into the mixture- forming rock candy!).

    The terminology is slightly different for air (although air and water are both fluids), but the general process is the same.  Fog fluid is heated and dissolved into air, then the warm mixture is exposed to ‘cool’ (room temperature) air, and so the fog fluid changes from a high-energy gas to lower-energy small water particles which the eye perceives as fog.

    This sort of fog immediately starts rising upon exit from the confined machine (heat rises) and will typically stick around a bit longer than cryogenic fogs.  Exactly how this fog behaves is highly dependent on the environment: temperature, relative humidity levels, and (of course) air currents all play an enormous role.

    The specific chemical makeup of the fog fluid used also impacts the behavior of the fog: fluid with only water will not last as long as a mixture of fluids.  Generally, fog is made using a ratio of water to either glycol or glycerin, which come from the alcohol family (although unlike ethyl glycol, it is not recommended for humans to ingest these) and readily dissolve in water.  The glycerin/glycol raises the boiling point of water, so heaters in fog machines have to heat the fog fluid to a higher temperature, but it also takes longer for the room-temperature air on stage to heat the fluid particles up enough to re-dissolve it.

     

    Since it’s known that long-term exposure to particulates is not particularly good for humans, Actor’s Equity Association (the union for professional actors) has developed guidelines for how dense any particular cloud of smoke that a performer must stand in can be.  More information as well as a study commissioned by AEA to determine the affects of fog, smoke, and haze on its members can be found here.

     

    Further Reading:

    ESTA’s Technical Standard’s Protocol: “Introduction to Modern Atmospheric Effects” (scroll to bottom)

    Actor’s Equity Association’s “Theatrical Smoke and Haze Regulations”

    Wikipedia’s “Theatrical Smoke and Fog”, “Supersaturation”, and “Cloud Physics”

    Lighting Lounge’s “Hazed and Confused- the Differences Between Fog, Haze & Dry Ice”

    Theatre Effect’s “Fog FAQs”

    Limelight Production, Inc’s “Fog Effects for Stage and Studio”

    New York Time’s “Where There’s Smoke, There’s Stagecraft”

    American Theatre’s “A Hazy Shade of Theatre: The Case for Clearer Design”

    Encyclopedia Britannica’s “Glycol”

    Film

    Aerial Fireworks

    September 7, 2018
    A History of Fireworks

    The history of fireworks begins with the history of gunpowder in 9th century China.  Gunpowder was probably invented by accident (the compound is a mixture of only three components) but was soon used at both wars and festivals.  Within about a hundred years of the invention of gunpowder, some form of early fireworks were being sold by Chinese street vendors.

    Gunpowder spread to Europe in the 14th century in the form of cannons and other military weapons, and with the gunpowder came fireworks.  In the 1800s, fireworks manufacturers began tinkering with the fireworks compositions and soon colored fireworks (and other effects) were lighting up the sky.

    Anatomy of an Aerial Shell

    Aerial fireworks shells are either a sphere or a cylinder, with spheres being more common.  Common sizes range from three inches (slightly bigger than a tennis ball) up to ten inches (about the size of a basketball).  Shells larger than ten inches are extremely expensive to transport, although they can be legally bought and shot.

    A spherical aerial shell is composed of five general parts: the casing, the stars, the flash powder, the time fuse, and the lift charge.  As sparks from machines are deadly in fireworks manufacturing, every firework is made by hand.

    The casing is two halves of a ball (for spherical shells), made from layers of paper.  Each half is filled with stars and then the halves are (carefully!) pressed together and taped.  To reinforce the weak seam created by the separate halves, the casing is finished with several layers of glue and paper strips.

    Stars are the exciting part of the shell: these are what provide color and most of the effects one observes.  Stars can be manufactured in several different ways; rolled stars are most common in commercial fireworks.  Rolled stars are round and range from the size of a pea to the size of a small grape.  Rolled stars allow for color-changing effects: as one layer is burned away, another layer of a different pyrotechnic composition (ie color) is revealed.  The colors are made by burning metals: titanium and aluminum burn white, barium burns green, copper burns blue, etc.  Those experimenting with new pyrotechnic compositions for stars must be careful about which chemicals are mixed together, as some chemicals react poorly with each other and will result in self-ignition.

    Flash powder is placed between the two halves of the star-filled casing and is responsible for fireworks going “Boom!”.  Once the flash powder is lit, the reinforced shell casing will initially resist the force of the expanding gases: this allows time for the stars to light.  The internal pressure will eventually overcome the paper casing and the firework will explode with the sound of a cannon to display its burning stars.  ‘Salute’ shells, with a larger-than-average ‘report’ contain more flash powder than ordinary shells.

    Time fuse is what lights the flash powder and what determines when the firework should explode after it has been launched.  Holes are pre-drilled in one half of the casing, allowing for one or more fuse(s) to be inserted into the firework.  Time fuse is similar to 3/8” rope, but is manufactured to burn at specific rates: 3sec/inch, 7sec/inch, etc.  The number of seconds needed for the shell to reach peak height is calculated (a shell should explode at the apex of its trajectory), and the needed length of fuse is cut and inserted into the shell.

    Finally comes the lift charge and fuse to light the shell (often quick match).  The lift charge is simple: several ounces of gunpowder to get the shell in the air and light the time fuse.  On commercial shells this may be contained in a cone, or in a small cup similar to a Dixie cup.  Quick match is another fuse covered in paper: almost as soon as it ignites, the paper carries the fire and lights the lift charge.

     

    The operator will then load the firework in an appropriately-sized tube (mortar), lift charge down, and either leave the fuse dangling out of the mortar (for hand-fired shows), or attach an electronic match (for electrically-fired shows).

     

    Problems with Shells

    Unfortunately, we live in an imperfect world.  And in that imperfect world, shells don’t always go off as planned (or at all).

    First is flower pots.  Flower pots never make it out of the mortar, instead throwing their bouquet of stars from inside their tube with a tremendous “Bang!”.

    Next is hangfires- arguably the worse of the potential problems.  A hangfire is a shell which has been lit, but has not yet left the mortar for whatever reason.  These are Schrödinger’s bombs: while still in the mortar they are simultaneously misfires and duds and may continue to be so for thirty minutes to an hour.

    Misfires can be bad.  Like, this-is-the-reason-you-never-put-any-part-of-your-body-over-a-loaded-mortar bad.  Misfires go randomly: either early (ignited by falling embers) or late (a smoldering misfire decided to light).  If you’ve ever seen one random shell go off several minutes after the show, a hangfire turned into a misfire.

    Duds are, as their name suggests, inert.  The firework may have gotten wet, it may not have been lit, the time fuse didn’t catch… generally something went wrong and the firework didn’t go off.  A dud may be found either in its mortar, or in the fallout zone around the fireworks area (this is the main reason why fireworks crews bar entry to what otherwise seems like the perfect place to watch fireworks: a grapefruit hurtling towards earth at terminal velocity).  Duds are rendered completely inert with water, and then transported back to the fireworks supplier for proper disposal.

     

    Regulating Bodies

    Fireworks are explosives and so are potentially subjected to federal, state, county, and city regulations.  On the federal level, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) covers firework requirements when the fireworks are not in transit and the Department of Transportation (DoT) rules when fireworks are in transit. 

    On the state level, most states have adopted various versions of the National Fire Protection Agency’s (NFPA) 1123 or 1126 standard (depending on the type of firework).  Fireworks operator’s are licensed on the state level and applicants generally have to provide evidence of working on shows as well as passing a written test based on state law.

    The local level is where the Authority Having Jurisdiction (AHJ) usually resides, as well as local laws about prohibited fireworks.

    Further Reading

    Wikipedia’s “Fireworks”

    Wikipedia’s “Gunpowder”

    ATF’s “Fireworks”

    DoT’s “Fireworks”

    America Pyrotechnics Association’s “State Law Directory” for Consumer Fireworks

    Film

    Stunt Falling from Height

    September 3, 2018

    Researching fire stunts last week got me into a ‘stunt-y’ sort of mood, and what is one of the next logical stunts to examine?  Falling from height!

    My initial research only brought up people who had performed incredible high fall stunts.  In the Assassin’s Creed (2016) movie, stunt performer Damien Walters jumped from 125ft in the film’s Leap of Faith stunt.  In a Twitter tweet, the Assassin’s Creed team touted the stunt as the highest free-fall for a film performed in 35 years.  The movie that the tweet referenced was likely Sharky’s Machine (1981) where stunt performer Dar Robinson leapt 220 feet from Atlanta’s Hyatt Regency Hotel.  In the movie, however, only the beginning of the stunt is shown.

    While not involving art in any way, Luke Aikins 2016 free fall from 25,000 feet deserves an honorable mention.  The daredevil jumped out of a plane without either a parachute or wingsuit and, after a two-minute free-fall, landed in a custom net.

    At the end of the fall, all that truly needs to happen is to decelerate the jumper until they are moving with zero velocity (ie stopped moving).  Over the years the way this deceleration has occurred has changed.

    In film’s Western era, stopping falls relied quite a bit on breaking wood.  Stunt teams would set up sawhorses around a crash site and delicately place a few pine boards on the sawhorses.  Cardboard boxes would be placed under the boards, and some mattresses on top.  When the stunt performer hit the mattresses, the boards would be put under stress and would begin to bend.  After a few inches of bend (and some reduction in velocity for the performer), the boards would break, and the performer would continue their slowed fall into the cardboard boxes.

    High falls performed in this way were limited to below 50 feet, as that was all the stunt performers could handle.  Additionally, this way of performing the stunt was highly wasteful: the boards were broken, and the crushed cardboard boxes would not be reused for another fall.

     

    Cardboard boxes continue to be used for lower falls today, as can be seen in this clip from an old episode of Fear Factor, when contestants were asked to drive a car off a building and into an (enormous) stack of boxes.

    Nets, as demonstrated above, can be used for high falls, as well as for lower falls common in circus activities.

    Bungee jumping has also become somewhat popular in films, as a stunt performer can be filmed from above without a need to erase their crash pad during post production.

    The most accepted way of decelerating a stunt performer at the end of a high fall, however, is with an inflatable stunt air bag.

     

    Inflatable Stunt Bags

    The beginnings of inflatable air bags started in 1959 by John Scurlock as he attempted to create an easy-to-store, easy-to-deploy tennis court cover.  As he tinkered, he noticed that his son enjoyed jumping on the inflatable mattress, and soon inflatable “moonwalks” were invented, followed eventually by the forerunners of bounce houses.

    It did not take long for others to connect the child’s plaything with the fire nets firefighters were currently using to catch people trapped in burning buildings.  The trick then, as is now, is how to cradle the jumper so that they don’t hit the inflatable pad and immediately bounce off it.

    Inventors soon realized that the trick was to vent the air the jumper displaced.

    A 1973 US patent (filed by the same John Scurlock) called for two air cushions stacked on top of each other: the top six feet in height, the bottom only three feet.  As the jumper falls into the bag, the pressure build-up due to a decrease in bag volume eventually opens “breathers” on the side of the bag.  With six feet of cushioned air to fall through, Scurlock calculated that a jump of 100 feet would be totally (and safely) stopped by the top cushion, but added the second, non-venting pad as a backup safety feature.

    Scurlock also included equations in his patent, showing that the difficulty is in successfully balancing an energy equation.

     

    The Equations

    This is a reproduction of the equations filed in John Scurlock’s 1973 patent and changing technology may have rendered these equations useless.  If you are trying to figure out how to safely perform a stunt, I applaud your effort, but suggest that you find someone with previous experience to work with you.

    1).   Aa = 8(1+3d- ((2d2)/h))

    Aa is the affected area of depression

    d is the depression

    h is the height, or thickness, of the air cushion

    I have no idea where this equation came from.

    2).   Vloss = 8(d+(0.9d2-((0.6d3)/h))

    Vloss is the volume of the air cushion lost due to depression

    d and h continue to be the depression and height of the air cushion, respectively

    As velocity is the mathematical integral of acceleration, this equation is (mostly) the integral of equation (1) with respect to d.  It is stated that this equation was found after realizing that the depression takes the approximate shape of a cone.

    3).   Pt= 15(Vloss/Vi) + Pg

    Pt is the pressure at any particular depression

    Vloss is the volume lost

    Pg is the initial pressure in the cushion (typically 0.5 psi in 1973)

    4).   Or by combining equations (1) and (2),

    Pt= (120/(Ai*h))*(d+0.9d2 – ((0.6d3)/h)) + Pg

    Pt, h, d, and Pg remain defined as above

    Ai is the total surface area of the cushion

    5).   F = 1000Pt(1+3d-((2d2)/h))

    F is the upward force of the air cushion on the falling body.  This is essentially the same force that a chair exerts on you as you sit on it.

    This equation comes from Force=Pressure*Area, with 1000 likely as a conversion factor.

    6).  Fmax = 1000k(1+3d-((2d2)/h))

    Where k is likely a modifying factor based on the height of the air cushion (?).  The patent contains a table which is not well-described.

    7).   Work = F*D = F ʃd = 1000Pavg(1+3d-((2d2)/h))Δd

    Pavg is the average pressure in the air cushion

    Work is defined as force occurring over distance: mathematically one does the same work running a 5k as one does walking it.  An integral is just mathematical shorthand for “find the (obnoxious) summation of the area under this line”

    8).   Pm = 3.3/(1+d)

    Pm is the maximum pressure allowed in the air cushion

    No idea where this formula came from, but it is likely something that a manufacturer will list.

    9).   Va = 350(P)1/2

    Va is the velocity of the escaping air (ft/sec)

    P is air pressure (psi)

    I suspect this is also something for the manufacturer to concern themselves with, and inform the client of.

    Other Useful Equations

    10).   Potential Energy = weight*height

    This is a physics formula, for the potential energy of the falling performer.  This is equal to the performer’s kinetic energy:

    11). Kinetic Energy = ½ mass*velocity2

    Essentially, any person high in the air has potential energy: if the floor suddenly disappeared, they would begin moving.  As a performer has chosen to convert all of their potential energy to kinetic energy, potential energy equals kinetic energy.  From this equation, one can calculate the performer’s velocity the moment before they hit the bag:

    12).   Velocity = (2*g*height)1/2

    Where g is the universal gravitational constant (32.2 ft/sec2).

     

     

    So there it is: as the performer falls, they will reach the inflatable air bag with some velocity depending on their weight and height they’re falling from.  The moment they impact the bag, it begins to depress with affected area Aa and after a few moments to allow the internal air pressure to build, the air will vent out of the bag through “breathers”.  At any point, the air bag is acting on the performer with a force F which is dependent on the pressure in the bag and the affected area Aa.

    For further information (including a sample calculation and location of breathers, I would highly recommend looking at the patent).

     

    Further Reading

    United States Patent

    GamesRadar’s Assassin’s Creed Jump

    Polygon’s Assassin’s Creed Jump

    Wikipedia’s “Dar Robinson”

    USA Today’s Skydiver Stunt

    Wired’s Physics Behind Skydiver Stunt

    NPR’s “Hollywood ‘Stuntman’! Reveals Tricks of Trade”

    Wikipedia’s “Inflatable Castle”

    Film

    Full Burn Film Stunts

    August 25, 2018

    One of the main reasons that I chose to go to school in Middle-of-Nowhere, Missouri is that my school offers pyrotechnics classes down at the “on-campus” experimental mine.  It was during one of these classes (the very first day, actually) when I got a second-degree burn by wearing pants with too much spandex in the blend.

    From staring at the dime-sized burn, it was only natural to wonder: “How do I avoid this happening next time?” and then it was a hop, skip, and a jump to, “How do stunt people set themselves on fire without injury?” And so I present:

     

    Full Burn Film Stunts

    To start off, this is one of the more dangerous stunts that professionals do: you should not try this at home.

    With that said, a full body burn is all about the set up.

     

    Before the Stunt

    First, an undershirt, long underwear, and a hood is soaked in a specially-formulated gel.  This gel is the key part of what protects the performer and is made with a (trade-secret) compound which absorbs a ton of water.  The water is held in the gel as tiny droplets, with millions of droplets in a glob of gel.

    Water has a high latent heat– it takes a lot of energy for water to change from ice to liquid, or from liquid to vapor.  Like ice cream on a hot day, as long as you eat it quickly, you can enjoy your frozen treat.  In stunts, as long as the burn is performed quickly (before the water has had time to boil off), movie-goers can enjoy the finished effect.

    The underclothes are no ordinary material either.  They are usually made from Novex or Kevlar which are fabrics that firefighters wear.  If heat is applied to Kevlar for more than a few seconds, it will start to burn.  If that heat is taken away, the flame will extinguish itself within a few seconds.  Novex doesn’t burn at all but will simply char and flake away.  As both are impregnated with the no-burn gel, they are highly unlikely to catch on fire.

    The next trick is that all parts of the stunt- clothing, gel, and performer- are kept as cold as possible, for as long as possible.  This is to prevent the water droplets in the gel from boiling off early, either due to energy from the sun or heat from the performer’s body.  Clothing and gel are kept on ice, and the performer is shooed into the shade.

    The performer next slides into the gel-soaked clothes and proceeds to slap no-burn gel on all exposed skin.  Any skin not covered with the thick gel risks being burnt.  A costume made of only natural fibers is then worn on top of the Nomex and gel.

    Meanwhile, other crew members have prepared the set- putting down a fire blanket or wet furniture blanket where the performer will be ending their stunt, and gathering and testing fire extinguishers.  CO2 fire extinguishers are often used and, as they put out the fire by starving it of oxygen instead of removing the heat, a water hose is often nearby for if skin was accidently left un-gelled and heat needs to be quickly removed (the high latent heat of water in use again!).

     

    During the Stunt

    Finally the time has come, the fire extinguishers have been manned, and the performer gets into position.  As the performer has just spent a fair amount of time becoming inflammable, burn gel is now applied to them so that something is able to catch on fire.  Burn gel (or burn paste or any other mixtures used) have one main trick: they burn at a lower temperature than fires usually experienced in life.  This allows the no-burn gel to last longer and for stunts to be more elaborate.

    The burn gel is applied, the performer is lit, and the rehearsed movements are acted.  One less-obvious safety consideration is practiced here: the performer is almost always moving forward.  This keeps both flames and (more importantly) hazardous smoke out of their face.  If the performer is asked to stand still for a shot, they hold their breath, and the length that the stunt can be safely performed is greatly reduced.

     

    After the Stunt

    At the end of the take (or if the performer is feeling unsafe), they go to the prepared blanket and drop to their knees.  This is the signal to those manning the fire extinguishers, and the flames on the performer are quickly smothered.

    The director examines the footage that was just shot as the stunt coordinator checks in with the performer, with medics hovering nearby.  If the performer is fine and the director asks for the shot to be done again, the performer applies more gel and re-does the action.  Once the director is happy with the footage, the performer retires from scene to go take a long hot shower.

     

    Want to read more?  Check these out!

    NPR’s “Trial by Fire- Literally- in ‘The Full Burn’”

    Wired’s “We Watched an Artist Set Fire to Themselves On Stage”

    Popular Science’s “Gray Matter: In Which I Set Myself on Fire”

    How Stuff Works “How Stuntman Work”

    StackExchange’s “How do they shoot flaming human scenes?”

    Wikipedia’s “Fire Retardant Gel”

    Explain That Stuff’s “Nomex”

    Action Factory’s “Fire Resistant Suits and More”

    TBF Pyrotech’s “Fire Paste and Fire Gel”

    Roger George Rental’s “Pyro Gel”

    Misc

    Girl Scout’s Entertainment Technology Badge

    August 16, 2018

    I’m not a girl scout.  Nor am I a girl scout leader.  But I was a girl scout growing up and I’m working to become an ‘entertainment engineer’.  I was cruising around for topics this morning and came across the Girl Scout’s Entertainment Technology badge for Juniors and realized “Yes!  This is something I can write about!”.

    Hunting around for the badge requirements, I found a five-step list on the girlscouts.org website:

    1. Animate your own artwork
    2. Dig into video game development
    3. Try the science of amusement park rides
    4. Create your own special effects
    5. Surf a sound wave

    My ideas are untested, but here is how I might geek out with some girls:

     

    Animate Your Own Artwork

    Animation is used all around us!  Animation is simply a series of moving images, and can be found on smartphones, computers, film…

    This is something I did at my internship this summer and surprised quite a few people with!  I created an image in Microsoft Powerpoint, saved it, slightly changed the image, saved it, and continued this process until I was happy with it.  I then searched for an online gif maker, uploaded my images, and downloaded my new animation!

    The analog version of this would be a simple flipbook!  Staple some index cards together along the short end, and ask your girls to draw an image that changes slightly on each successive card.  Quickly flip through the book and- voila! Animation!

    Researching around, quite a few blogging leaders were interested in Claymation- used in films such as Wallace and Gromit (2005), Chicken Run (2000), Coraline (2009), ParaNorman (2012), and The Nightmare Before Christmas (1993).  The problem with movie Claymation is that it’s super time-consuming, and thus super-expensive.  But that doesn’t have to be a problem for you!  Grab some clay (or maybe even Play Dough) and remember to keep it simple!  Generally you want at least twelve “frames” (or snapshots) a second for a smooth animation, most films are shown at 24 frames per second, and video games are usually between 30 and 60 frames per second!

    A last fun idea that I’m going to leave with you here is the Victorian zoetrope.  Think of this as a spinning round cake pan.  You have a strip of paper on the inside of the wall of the pan, and slits are cut between the images.  Bend so that your eyes are level with the edge of the pan (so you can only see through the cut slits) and spin the entire thing.  As the pan spins, the images will move, and a ‘smooth’ transition will occur since the edge blocks the abrupt transition for image-to-image.  The faster you spin the zoetrope, the smoother the animation will seem.  Making a zoetrope could be a neat activity, but it would probably require the most work.

     

    Dig into Video Game Development

    After a quick google search, there are ways to do this if you want to go all-out.  A search for “make a video game” brings up Gamefroot’s Game Editor, Flowlab’s Game Creator, and Buildbox’s Make Your Own Game.  It also bring up a Digital Trends article about a journalist who was able to make a video game having no previous experience with code in about… 10 hours.

    Personally, that’s a little longer than I would want to spend on a single step in a badge.

    Reaching out for help, most leaders seem to use this as a guest-lecture portion: trying to find students at local universities or a well-done YouTube video.

    Sniffing around, I found this and this which are about ten minutes total.  There are longer videos that go more in-depth, but I thought those would best be left for individual exploration, if any of your girls want to do more research.

     

    Try the Science of Amusement Park Rides

    For an activity, plastic marble roller coasters (or a budget-friendly version) seem to be popular.  But there are other things to explore here!

    Design a lazy river- use sand and a fan to check curve radii (hint: tight curves will make for choppy water and an un-relaxing experience!).

    Check out centrifugal force (angular momentum)!  Have girls hold hands and spin in a circle.  How easy is it to begin with their arms fully extended and pull themselves closer?  This can also be done on spinning chairs- have the girls extend and bring in their legs.  They’ll spin faster if their legs are closer to them!  The physics here are used in a Rotor ride (seen here).  On the ride, the rider’s body essentially wants to keep moving in a straight line (objects in motion tend to stay in motion).  Because the round room prevents that, the rider sticks to the wall even when the floor is removed!

    What sort of safety features might be used on roller coasters?  What safety features are used?

    What are some of the physical feelings you experience on a roller coaster (g-force)?  Going down a drop, riders are often in free-fall for a short period of time and so experience zero-g’s (the same thing astronauts feel in space!) while when speeding up a hill or coming out of a loop, riders may feel multiple-g’s.  You can also feel g-force when you take off in an airplane or plop down in a chair!

     

    Create Your Own Special Effects

    This is where you can have a ton of fun!  There are loads of possibilities here- ask around and see if any parents have any special skills they could share.  Personally, I know some stage combat and would love to show girls how movie fights are done safely.  While it’s specialized, my school also has a pyrotechnics program and they occasionally do demonstrations for kids.

    If you don’t have access to any special resources, you’ll have to be a bit more creative- which is the entire point of special effects!  Two ideas immediately come to mind for me: gore makeup and Foley effects.

    Working with and around actors has somewhat ruined me for movies- instead of believing everything I see, I instead look for how it was done.  Gore and special effects makeup is an awesome example of that!  Find a good (washable!) recipe for blood (usually some form of cornstarch, food dye, and water) and get a makeup kit suitable for bruises and let your girls go to town!

    For a less messy activity, check out Foley effects.  Foley is creating effects for film after the movie has been shot, and often involves very different objects than the ones seem on-screen.  For example, the slashing ‘Z’ heard as Antonio Banderas opens The Mask of Zorro (1998) is made not with a sword, but with a wooden dowel.  The Kill Bill movies apparently went through quite a few melons as they needed to slice through human heads, and, of course, most know of the clapping coconuts for horse’s hooves.

    See what sounds you can make with everyday objects!  Have girls take turns closing their eyes and guessing the effect as others create it!  Foley is awesome!

     

    Surf a Sound Wave

    For this, I would spend some time on the science of sound.  Sounds exist as waves and dissipate over distance (thus the point of whispering).  To visualize this, have a still tub of water and drop an object in.  The object disturbs the water, which sends out waves which become smaller the further away from the object.  The waves also interact with each other, depending on if they hit the side of the tub and bounce off it or not (can someone understand you if you yell at a wall?  Probably!  Can you still understand them if there are other people talking at once?).

    Sound waves also have different frequencies- a higher voice versus a lower voice.  This can be seen in the waveform as how many up-and-down bits happen in a certain amount of time (say, one second).  Higher frequencies have more ‘disturbances’ jammed into them than lower frequencies.

    High frequency wave (left) and low frequency wave (right)

     

     

    You can model this with a jump rope: have a girl on either end and have one of them jerk the rope up and down once.  You can see the wave travel across the rope!

    This is cool because what frequencies we can hear changes throughout our life!  Try it! Your girls should be able to hear a wider range of frequencies than you can!  Throughout our life we damage our hearing and lose the ability to hear higher frequencies.

    Sound engineers know what general range of frequencies adults can hear and will use that knowledge to their advantage.  In horror films, sounds lower than what adults can hear will sometimes be played, because while it cannot be heard, the sound can still be felt and will put people on-edge.

    Occasionally, frequencies higher than most adults can hear will be played, either on accident or deliberately to drive away insects, small animals, and teenagers.

     

    So there you have it.  Here are some ways that I would geek out with girls to earn this badge.  I’m not sure that I could earn this badge in a single meeting (because I would want to spend more time on time-consuming activities) but I think we would have enough fun that no one would mind stretching it out too much!

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