Thanks for the insight! That confirms my suspicion I had after reading up on it. It seemed to me that the platinum-catalyzed silicones have less shrinkage (essentially none) and don't produce alcohol like tin-catalyzed silicones do. I thought, "Man, these sound even better than the tin-cat silicones to me but I never hear of anyone using them that way... Better ask the invisible online masters." I couldn't seem to shake the thought that plat-cat silicones are best as a skin, not a mold, despite the gazillion different hardnesses and viscosities available.
Alrighty then, I think I'll give Platsil 73-29 a shot and will let you guys know how it works. I'm really looking forward to it--especially because the 15,000cP viscosity is MUCH better than GI-1000's 50,000-70,000 for what I'm doing.
Just curious, it seems to me that with the proper release agent, I could probably cast Dragon Skin or PlatSil Gel-10 in a plat-cat mold with no issue, ya? Methinks I might be able to paint a plat-cat skin and fill it with foam latex. I know plat-cat silicone hates foam latex, but as far as I know foam latex is amicable with all silicones. That is, until I get up the courage to tackle this Soma Foama deal (of course I mean courage to face my wife after buying another new expensive chemical, not from trying something new; I actually like that part) ;)
Duane
Reply to discussion
Platinum cure silicones are perfect for making molds, as a matter of fact - with some casting materials, it's mandatory. There are lots of casting materials that will not cure properly if cast in a Tin Cure mold. Some of the platinum cure silicones can be really tough rubbers and that's great for the life span and accuracy of mold keeping it's shape when casting out of it. So Yeah, platinum cure silicones are great for molds and you always need to check the compatibility factor when picking a new casting material. You can always find the material's data sheet online and there's always info in them about bad reactions with which cure type silicone so, do your homework whenever you try a new casting material.
I don't remember ever using the TinSil 70-30 or PlatSil 71 or 73 specifically (there are SO many!) but they are all good products in my opinion and the only real differences are hardness and cure times. So when you pick a silicone to use, go to the Polytek website and look up each product and compare the differences. There are so many versions because it's best to be able to tailor the material of choice to what's best for your specific needs. (fast cure for small simple molds, long cure for big complicated molds and/or de-airing in a vacuum chamber, etc...)
Lastly - If you're using your silicone for making molds, GI-1000 is probably a better choice but, that's only because I find it to be a stiffer rubber and will hold it's shape better without a 'mother mold' (or 'jacket mold' depending upon who you talk too) around it. But using Dragon Skin might be a better choice if what your casting has deep undercuts and you need something more flexible. They will both work fine, you just get 'a feel' for which is better for which project after you use all of them.
(Note- You can tell how hard a rubber will be by checking the 'Shore' letter, a rubber described as 'Shore A' will be super soft and stretchy and one referred to as 'Shore D' will be more like a rubber pencil eraser.)
I don't remember ever using the TinSil 70-30 or PlatSil 71 or 73 specifically (there are SO many!) but they are all good products in my opinion and the only real differences are hardness and cure times. So when you pick a silicone to use, go to the Polytek website and look up each product and compare the differences. There are so many versions because it's best to be able to tailor the material of choice to what's best for your specific needs. (fast cure for small simple molds, long cure for big complicated molds and/or de-airing in a vacuum chamber, etc...)
Lastly - If you're using your silicone for making molds, GI-1000 is probably a better choice but, that's only because I find it to be a stiffer rubber and will hold it's shape better without a 'mother mold' (or 'jacket mold' depending upon who you talk too) around it. But using Dragon Skin might be a better choice if what your casting has deep undercuts and you need something more flexible. They will both work fine, you just get 'a feel' for which is better for which project after you use all of them.
(Note- You can tell how hard a rubber will be by checking the 'Shore' letter, a rubber described as 'Shore A' will be super soft and stretchy and one referred to as 'Shore D' will be more like a rubber pencil eraser.)
Tuesday, 09 November 2010 09:16