Wesley Scoggins
Indy Mogul
Wesley's Weekly HOW TO: Mouth Foaming
Something that has been requested recently is a way to produce a lot of foam from a mouth for scenes where people are having seizures, or for transformation scenes (like with zombies). While I have seen a lot of suggestions about what to use, I thought I would test a bunch of common foaming agents to see which would work best for your needs.
Rather that just start shoveling baking soda into my mouth and taking pictures of it (which I know EVERYBODY wants to see happen), I thought I would do this in a bit more controlled (and aesthetically pleasing) manner, and test the foaming amount, color retention (how well it holds food coloring), and foaming duration in some clear plastic cups (so you can clearly see what is going on).
First up, is this name brand effervescent tablet that I crushed up, you'll want to crush it up to increase the amount that is exposed to the liquid, thus increasing the speed at which it foams. If you don't you'll get a slow foam that won't look very dramatic, while crushing it up, then taking a swig of water will look much better and look more "explosive". (Warning, this and many other effervescent tablets, CHECK THE LABEL, contains aspirin, so don't swallow the foam, and avoid its use altogether for aspirin sensitive individuals.)
A few drops of green food coloring, and a splash of water, and it foams up quite well. The bubbles aren't huge, but the foam is nice and thick. How you'd generally do this trick on film is that you'd ask your actor to pop the tablets into their mouth, put a couple of drops of food coloring on each tablet before then (if you want it colored, you obviously don't need it colored if they are just having a normal seizure), have them crush it up in their mouth, then RIGHT before you needed it to burst out have them take a swig of water right before you cut to them and they can open up their mouth as it starts to foam out. It holds up color rather well, and you of course can use a lot more if you want it darker, but I think that this would show up really well in your films.
This is a store-brand effervescent tablet that was cheaper. Each packet only comes with one, but each tablet is also larger.
This brand held up the color REALLY well, but it has less dense foam, although the bubbling is stronger, and the bubbles much larger.
Vinegar and Baking Soda is a combination most of us know really well from our childhoods as the ingredients for the model-volcanoes many of us made in grade school. Well one great thing about this mixture is that baking soda doesn't readily react with the saliva in your mouth, meaning that the reaction is a bit easier to control, but also less pleasant to control, since your actor has to take a swig of vinegar to get the reaction going. While vinegar is not poisonous and the mixture is not dangerous (except in the rare case of an allergy to one of thes components obviously), it is not pleasant to have in your mouth, AND as you can see the reaction is VERY fast. It was so quick that I was actually unable to get my camera ready and capture it before it had already subsided (while in contrast the first effervescent tablet mixture was STILL bubbling). If you look closely you can see that the "flood line" almost reached the top of the cup, so it was a LOT of bubbles, but ONLY for a short time. For more explosive effects I think this could work decently well, but you're not going to get a long foam time from this mixture.
And finally, toothpaste. Toothpaste has a bunch of chemicals in it to facilitate foaming (as the foam is easier to clean your teeth with), and is something that is available to almost everyone for more or less free. BUT it's also one of the harder to get foaming since you literally have to swish it around in your mouth for a while before you can get it looking good.
It was hard to get it foaming, and it wasn't a lot of foam produced, but it's cost can't really be beaten, and most likely will be "enough" for whatever you want to do.
So there you go, hopefully this answers some of the questions some of you guys and gals had and helps you choose what you're going to be using for your mouth foaming scene in your upcoming movies.
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