Fayne
Well-Known Member
I just sent this info to a friend and thought others could use it.
Feel free to make additions or corrections and add pics if you'd like as I won't be to this step for a while.
Info......
I've been looking into different types of silicone but remember I look at things from a technical angle often as opposed to a brand name angle. I found info that might help you out a ton.
There are 2 kinds of silicone:
Platinum or addition cure, and
Tin or condensation cure.
Both types can come in RTV or room temp. vulcanising or can need heat to cure.
More often the platinums need added heat and are picky about what they touch, thus the name addition cure. These are the ones that cause issues around latex or around sulpher based clays. A lot of the FX stuff you'd use for skins and masks are platinum cure silicones. Platinums won't often (maybe ever) bond to fully cured silicone of any type so new coats are added while tacky.
Tin cures are more often found in RTV variants with an "eaqual parts" mix and are extremely forgiving about chemicals present.
They can often (depending on manufacturer and product) be used around sulpher clays without issue. These are often used for box molds but are a bit weaker (tear strength) than the platinums that are often used for glove molds though you could use either and treat it with care as should be done anyway.
Tin silicone cures by using humidity (not liquid water) and has an oil as a biproduct (small amounts) This is why it's called condensation cure and why it doesn't always need a mold release to make though oiling or waxing to keep a mold in shape is still necessary.
100% silicone caulking like the GE stuff is a Tin/condensation cure but is packaged in the absence of moisture so ppl think of it drying in the traditional sense of losing moisture though it's actually gaining water and losing oil. It already has a thickening agent and doesnt get moisture if used too thick. To use it as a mold you would either thin with naptha or mineral spirits for your first thin coats. I'd just use brand name for the first few coats so I don't soften my clay and screw up the work. For subsequent coats you can use the GE silicone (not the regular caulking / only 100%) and to ensure it dries /catalyzes mix it with a small amount of acrylic paint which has a chemical that helps to catalyse the tin cure silicone. Not to mention the paint will show how well it's mixed. I'm thinking of experimenting with naptha or mineral spirits and acrylic paint all together to make it brushable but make bubble poppable and easier to avoid. I'd only do that on my later cots of coarse.
I almost forgot to mention, within each family silicone types are pretty much the same until catalyst is added. In other words the silicone part is often similar from type to type within it's respective tin or platinum family but the catalyst part of the mix could have a load of different ingredients to impart the different strengths and qualities of each type or brand.
Feel free to make additions or corrections and add pics if you'd like as I won't be to this step for a while.
Info......
I've been looking into different types of silicone but remember I look at things from a technical angle often as opposed to a brand name angle. I found info that might help you out a ton.
There are 2 kinds of silicone:
Platinum or addition cure, and
Tin or condensation cure.
Both types can come in RTV or room temp. vulcanising or can need heat to cure.
More often the platinums need added heat and are picky about what they touch, thus the name addition cure. These are the ones that cause issues around latex or around sulpher based clays. A lot of the FX stuff you'd use for skins and masks are platinum cure silicones. Platinums won't often (maybe ever) bond to fully cured silicone of any type so new coats are added while tacky.
Tin cures are more often found in RTV variants with an "eaqual parts" mix and are extremely forgiving about chemicals present.
They can often (depending on manufacturer and product) be used around sulpher clays without issue. These are often used for box molds but are a bit weaker (tear strength) than the platinums that are often used for glove molds though you could use either and treat it with care as should be done anyway.
Tin silicone cures by using humidity (not liquid water) and has an oil as a biproduct (small amounts) This is why it's called condensation cure and why it doesn't always need a mold release to make though oiling or waxing to keep a mold in shape is still necessary.
100% silicone caulking like the GE stuff is a Tin/condensation cure but is packaged in the absence of moisture so ppl think of it drying in the traditional sense of losing moisture though it's actually gaining water and losing oil. It already has a thickening agent and doesnt get moisture if used too thick. To use it as a mold you would either thin with naptha or mineral spirits for your first thin coats. I'd just use brand name for the first few coats so I don't soften my clay and screw up the work. For subsequent coats you can use the GE silicone (not the regular caulking / only 100%) and to ensure it dries /catalyzes mix it with a small amount of acrylic paint which has a chemical that helps to catalyse the tin cure silicone. Not to mention the paint will show how well it's mixed. I'm thinking of experimenting with naptha or mineral spirits and acrylic paint all together to make it brushable but make bubble poppable and easier to avoid. I'd only do that on my later cots of coarse.
I almost forgot to mention, within each family silicone types are pretty much the same until catalyst is added. In other words the silicone part is often similar from type to type within it's respective tin or platinum family but the catalyst part of the mix could have a load of different ingredients to impart the different strengths and qualities of each type or brand.
