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USING A/B COLD FOAM
A/B Cold Foams are easy and great to use for all kinds of applications. It is most widely used for props. In an emergency, I've seen the very soft flexible foam used for quick prosthetics when working out on set when an oven isn't to be had, or time just doesn't permit baking foam latex. When using as a prosthetic, use at your own risk. . .FX Warehouse will not be held responsible for injury or sickness due to this type of use.
READ YOUR MSD SHEET! If one didn't come with your kit, then request one. MSDs aren't an automatic attachment to your instructions. These Material Safety Data Sheets will tell you what your products are made of including safety precautions, what to do in case of spill and what kind of bodily harm it can cause. A/B Urethane foams are not healthy. Be aware of what you are using.
When using the soft (3.5 lb) foam to fill props, many prop builders first pour casting latex into the mold. After the latex is cured, pour in the A/B foam. This makes a skinned flexible prop. The rigid low density (3.5 lb) soft & rigid foams are also great for filling stagnant props.
When using the more dense (harder - 10 lb) soft & rigid foams the following process works best. This foam is dense enough you don't need to put a 'skin' in the mold first. It makes it's own skin. Great for Mummies & Corpses. Remember the 'Rule' when pouring up props. If the final piece is rigid you need a soft, flexible mold. If the final piece is soft you need a rigid mold.
In this demonstration I am pouring a soft piece. The mold I am using is a silicone mold made of Vi-Sil 1065 mold Silicone with a fiberglass casing.
A/B Foams are Urethane compounds. Urethane sticks to just about everything. And so the mold needs a release agent so the end piece doesn't stick to it. Even tho Tin Silicone gives off silicone oil as a natural release, when I use Urethane I make sure I use a good release agent. The simplest and cheapest release when using a silicone mold is ordinary dish detergent or bar hand soap. Wax releases also work well. I used Challenge 90 which is basically a wax dissolved in solvents. If you are using a plaster, fiberglass or urethane mold then use the Wax release.
To help support the mold I have a casing mold made of fiberglass, which has flanges around the edges where we screw the mold together. A/B foams can be pretty forceful at times, since they expand. The mold needs to be strong and tightly clamped shut or it may pull apart. I've seen A/B foams actually break a mold while expanding.
The A/B cold foam I used is a 3.5 lb density. Pot Life is 30 seconds. Which means, you have 30 seconds from the time the 2 components meet until it starts to rise. This particular foam will rise approximately 15 to 20 times it's original volume. The higher the density the less rise you get. And so, the 10 lb. foams will only rise 3 to 4 times it's original volume.
OK, let's get started. Equipment I used:
Dura Soft 3.5 lb. density foam (P168)
Challenge 90 Release
Silicone Mold with Fiberglass Casing
Plastic Sheeting for floor
Latex or Vinyl Gloves
Safety Goggles & Respirator
13oz Measuring Cups
Squirrel Mixer attached to Drill
Bucket for mixing
Assemble your chemicals and equipment. Put plastic down on the floor. Wear latex or vinyl gloves, a respirator and safety goggles. Work in a well ventilated area. I mix my foam outside.
Brush or spray the release agent into your mold and around the pour area.
Release agents recommended:
Dish Detergent or Bar Soap
Challenge 90 Release
Frekote Spray Release or any Paste Wax Release
Allow to dry and then clamp your mold together tightly. If it's clamped too loose the foam may cause your mold to open. If you do not have bolts or flanges use mold straps or heavy mold rubber bands.
It's recommended you use a gram scale but it isn't necessary. If you just measure by volume with measuring cups you may run out of the 'A' side eventually. But the foam will come out just the same either way, even if not measured exactly. I prefer using measuring cups. A/B foams all have different ratio mixes. Check your instructions for ratio of A to B.
I didn't color my foam but you can. Using only Urethane pigment add a little to the 'B' side of your foam before mixing. You'll have to judge the amount for yourself. But if you add too much it will keep your foam from raising properly. Pour part 'B' into the mixing container. Get ready with your squirrel mixer (this is a mixer that is added to a drill so you can mix very quickly). For very small pieces you can hand mix but you won't get the raise out of the foam like with a squirrel mixer. Placing the mixing container between your feet, and with the mixer ready, add part 'A'. You now have about 30 seconds before the foam starts raising and then you won't be able to pour it into your mold. Be quick. Mix the components 8 to 10 seconds at high speed. Don't worry, it's plenty of time.
Pour the mixing components into your mold thru the pourgate. Do NOT scrape the sides of the mixing container to get out every little bit of foam. There may be unmixed chemicals there and if it gets into your mold it may not raise properly. Free pour the foam and leave the rest in the container.
After the foam is poured do not knock the mold or it may cause the foam to drop. It will start raising within seconds. In bigger molds it is wise to have escape holes drilled in areas where the foam may become trapped. This will alleviate the problems of too compressed foam edges or even air pockets where the gases given off by the chemical reaction within the foam.
Most foams take about 20 minutes to cure. There will be some heat put off by the foam during the chemical reaction and so the mold will warm up and then cool down when it's cured. I usually wait 30 minutes before I open my mold.
The mold should come apart easily. If it doesn't then not enough mold release was used. But do not use too much mold release as it may puddle and keep the foam from expanding properly. Don't stress on this, as it hardly ever happens.
That's it. Your piece is done. Trim the edges. Paint it, if you wish. Urethane is not an easy material to paint. You can use Skin Flex paints, but they are highly toxic. I've used PAX paints with great results. The makers of Pros-Aide have just put out a new Tac-Free Pros-Aide. We, at FX Warehouse are doing research on making PAX paints just for this application.
As in the beginning of this posting I talked about slushing your mold with casting latex first and then pouring in the foam. With this type of application you can just paint your end piece with latex paint base in the colors you wish.
A note about the weather: Urethanes are moisture sensitive. If it's raining I try to avoid pouring up Urethane. Moisture can keep the foam from raising to it's full potential. If there is a piece that is still gooey, it may be because of moisture, or the batch not being mixed enough. After you've poured up the amount of chemical it's recommended you purge the containers. I use dry air in a can . . . you spray it in and it takes the moisture out of the container. Never leave the tops off containers.
Disclaimer: FX Warehouse Inc. will not be responsible for use of misuse of any products you may buy or use from us. Most of our products are for Professional Use only. Use at your own risk.