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”

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