Joined: Wed May 05, 2010 3:26 am
Location: Central California
Tips and Tricks for Using Silicone Rubber
General tips and tricks for using silicone rubber:
- Silicone rubber is thick, sticky, and messy when it is still a liquid. Keep a box of disposable gloves handy so that you can easily change gloves when you get silicone on them.
- Cover the area where you will be working with a piece of plastic sheeting or a plastic garbage bag. When you're finished, simply roll it up and throw it away.
- Collect plastic tubs, such as margarine or cool whip containers. These make easy (and cheap) mixing containers for your silicone, and you can bend them to make a good pour spout. Plastic cups are also good mixing containers, though they typically break if you try to bend them into a pour spout. Plastic spoons are good for mixing. Get a big box of them, and toss out each one after you use it.
- You don't want to use your good measuring cups for mixing silicone, because it's very hard to clean up afterwards. If you are measuring by volume instead of weight, here's a trick. Say you need to measure out 1/3 cup of each silicone component. Fill a 1/3 cup measuring cup with water. Then, pour that water into a disposable plastic cup. Mark the water line on the side of the cup with a Sharpie, and then pour the water into another cup. Mark that water line as well, and then pour out the water. Dry both cups thoroughly, and you now have two disposable, marked mixing cups!
- If you spill mixed rubber on a porous surface, clean it up while it is still a liquid. Acetone and mineral spirits both work. After using them, clean the area with dish soap and water.
- If mixed rubber is spilled on a smooth surface, you can usually just let it cure and then peel it off. Silicone doesn't stick to smooth surfaces. It does seem to lock onto glass for some reason, though.
- If you spill the unmixed components of silicone, they will not cure or harden. You will need to clean them with the acetone or mineral spirits.
- Silicone rubbers are sensitive to temperature and humidity. Always work in a room that is in the 70-degree range, with normal humidity. Very humid or too-low temperature conditions will inhibit the curing, while very high temperatures will make them set up too fast.
- If you are making your own sculpture, do NOT use a clay that has sulfur in it! The sulfur will keep your rubber mold from curing properly, and you'll end up with a gooey mess. I've heard that a good coating of Krylon will cover the sulfur and keep it from damaging the mold, but do you really want to take chances?
- Apply a sealer coating to your model before you make the mold. This will close up the pores and keep the silicone from seeping into them and locking the mold to your sculpture. Many people prefer to use Krylon Crystal Clear. Give it a full day to dry completely before you move on to the next step, or you may have problems with the sealer peeling off and sticking to your mold.
- The easiest way to estimate how much rubber you are going to need is to do a test run with water. Fill the mold space to the desired level, and then pour the water into a measuring cup to find out how much volume it took. That way you will know exactly how much silicone it will take, and you won't waste too much or run short. I usually mix a little bit extra just to be on the safe side... some will always stick to the sides of the mix cups, or get spilled a bit. After using water, be sure to dry the model and every other surface COMPLETELY before moving on. Any moisture left behind might cause problems when you pour in the rubber.
- Apply a release agent to the model and to every other surface your mold silicone is going to touch. I like to use Smooth-On's Ease Release 200 or 800. Spray on a light coat of release, then brush it over the surface of your sculpture and the surrounding clay and mold box with a clean, soft brush. I use a chip brush. (Use a Sharpie to write "Ease Release 200" on the handle, so it doesn't accidently get used for anything else!) Let that first coat dry for 15 minutes or so, and then give the model another light coating. Don't spray too much, or you will end up with a sponge effect on your mold surface. It only takes a little bit!
- When you are finished using a mold, if you want to keep it in good shape for later castings, here's the best thing to do. First, fill the mold with plaster. Be sure to leave the plaster inside the mold, don't take it off. This will help the mold hold it's shape for a long period of time. When the plaster is thoroughly dry, wrap the mold and plaster inside a plastic bag and seal it closed. (Make sure the plaster is thoroughly dry, or it will get mold spots! Yeah, that's a bad pun. Sorry!) Then, store the mold in a protected place, preferably in a box which will protect the mold from sun damage and from being squished or misshapen. Remember, once a mold loses it's shape... the damage is usually permanent!