Reply to discussion
Just wanted to give everyone here an update on my mold experience.
After listening to your advice, I went down to the store the next day to pick up some Platsil 73-29, but they were all out!
I figured I would come back later when they had some, but the lady at the store suggested I go with some of their 71-20, which apparently is the most popular blend they sell to sculptors. She said all the undercuts on my sculpt would benefit from the 20-shore hardness over the 29 as well. I decided to pick up a pack, partially to test out the material and partially to check out whether or not she would be a good reference on these things in the future, know what I mean?
Well, it was a success! There are a lot of undercuts on my piece simply due to the hair on the character... there really wasn't any way around it. But the mold is nice and flexible and I can sort-of muscle the piece out of there by bending the silicone, and it comes out beautifully. So far I have had 3 or 4 good pulls from the mold and haven't experienced any problems, and I really don't need very many more casts. The lower viscosity on this stuff, compared to the GI-1000 of which I am accustomed, was fantastic. I think there was only one or two small bubbles on the whole thing. And the silicone was SO effective that it even slid between the lumps of clay hair and his scalp! I had no idea it would be thin enough to fit in those tiny areas. What a great problem to have! haha
I am new to this forum, so I will try to post a picture I took as soon as I find out how.
Also, as an aside, one small pack of this stuff was not enough for both halves of the mold, so I had to wait (and wait) until their next shipment arrived, hence the delay in me posting an update. The stuff really didn't give me any problems and I could've finished it a day or so after posting my original message if I had bought enough the first time.
Thanks for the advice, my friends.
Duane
After listening to your advice, I went down to the store the next day to pick up some Platsil 73-29, but they were all out!
I figured I would come back later when they had some, but the lady at the store suggested I go with some of their 71-20, which apparently is the most popular blend they sell to sculptors. She said all the undercuts on my sculpt would benefit from the 20-shore hardness over the 29 as well. I decided to pick up a pack, partially to test out the material and partially to check out whether or not she would be a good reference on these things in the future, know what I mean?
Well, it was a success! There are a lot of undercuts on my piece simply due to the hair on the character... there really wasn't any way around it. But the mold is nice and flexible and I can sort-of muscle the piece out of there by bending the silicone, and it comes out beautifully. So far I have had 3 or 4 good pulls from the mold and haven't experienced any problems, and I really don't need very many more casts. The lower viscosity on this stuff, compared to the GI-1000 of which I am accustomed, was fantastic. I think there was only one or two small bubbles on the whole thing. And the silicone was SO effective that it even slid between the lumps of clay hair and his scalp! I had no idea it would be thin enough to fit in those tiny areas. What a great problem to have! haha
I am new to this forum, so I will try to post a picture I took as soon as I find out how.
Also, as an aside, one small pack of this stuff was not enough for both halves of the mold, so I had to wait (and wait) until their next shipment arrived, hence the delay in me posting an update. The stuff really didn't give me any problems and I could've finished it a day or so after posting my original message if I had bought enough the first time.
Thanks for the advice, my friends.
Duane
Sunday, 09 January 2011 00:19
i may be mistaken but the 71 and 73 #'s refer to the shore hardness . platinum catalyzed silicone is stronger [more casts] and has less adverse reactions to other materials , but it cost more . i have only used the smooth on stuff so iam sorry i can't give you a comparison .the best thing to do is vist the many different distributors sites [ like smooth on ect...] there is a ton of info out there.
Tuesday, 09 November 2010 22:50
I agree about this group - piggybacking of Ron's experience has helped me make the transition to silicone puppet skins with fewer stuff-ups!
I used Polytek Platsil Gel-10 for casting puppet heads, and I think it is virtually identical to Dragon Skin. I haven't used the shore 10 Dragonskin, but I did cast a head in the slightly softer Ecoflex 00-30 from Smooth-On. Except for the slight difference in hardness they were exactly the same to use. Both work with Psycho Paint and the Sil-Pig pigments.
I have used several mouldmaking silicones in the past, and they were all pretty similar, so the main thing is to get the hardness that suits your mould. The only drawback with tin cat is it's sensitivity to so many materials - but if you sculpted from a non-sulphur clay, it should be great for making a mould.
I would not fill a silicone skin with foam latex - it would not stick very well. Same with a soft 2-part urethane foam, it would not bond onto the silicone skin. I go the other way, and stick some urethane sheet foam on the armature, before pouring the silicone in to fill the mould - the liquid silicone bonds nicely onto the porous surface of the cushion foam. I haven't tried filling with Soma-Foama yet, I think Ron's the only one with experience of that, but it should bond to the skin which is what you want.
I don't know if Hydrocal is an equivalent to Ultracal or not - I mostly use Hydrostone, which works perfectly well for casting silicone or foam latex. For that matter I've cast foam latex in plain old casting plaster - it doesn't last through as many bakes but is ok for 2 or 3 casts. Not ideal but you can get away with it, so I figure Hydrocal would be much better than that.
I have a figure sculpt in Chavant NSP that is nearly ready for mouldmaking, which I will be casting in Ecoflex 00-30. I'm considering making the mould from epoxy resin instead of Hydrostone or other plaster, since I won't ever be casting it in foam latex or baking it. It would be a lighter, more compact mould and there is no risk of fine details ever breaking off. I'll do a test with the Ecoflex silicone on the epoxy, just to be certain it doesn't inhibit the cure, but if that works I will probably go for it.
I used Polytek Platsil Gel-10 for casting puppet heads, and I think it is virtually identical to Dragon Skin. I haven't used the shore 10 Dragonskin, but I did cast a head in the slightly softer Ecoflex 00-30 from Smooth-On. Except for the slight difference in hardness they were exactly the same to use. Both work with Psycho Paint and the Sil-Pig pigments.
I have used several mouldmaking silicones in the past, and they were all pretty similar, so the main thing is to get the hardness that suits your mould. The only drawback with tin cat is it's sensitivity to so many materials - but if you sculpted from a non-sulphur clay, it should be great for making a mould.
I would not fill a silicone skin with foam latex - it would not stick very well. Same with a soft 2-part urethane foam, it would not bond onto the silicone skin. I go the other way, and stick some urethane sheet foam on the armature, before pouring the silicone in to fill the mould - the liquid silicone bonds nicely onto the porous surface of the cushion foam. I haven't tried filling with Soma-Foama yet, I think Ron's the only one with experience of that, but it should bond to the skin which is what you want.
I don't know if Hydrocal is an equivalent to Ultracal or not - I mostly use Hydrostone, which works perfectly well for casting silicone or foam latex. For that matter I've cast foam latex in plain old casting plaster - it doesn't last through as many bakes but is ok for 2 or 3 casts. Not ideal but you can get away with it, so I figure Hydrocal would be much better than that.
I have a figure sculpt in Chavant NSP that is nearly ready for mouldmaking, which I will be casting in Ecoflex 00-30. I'm considering making the mould from epoxy resin instead of Hydrostone or other plaster, since I won't ever be casting it in foam latex or baking it. It would be a lighter, more compact mould and there is no risk of fine details ever breaking off. I'll do a test with the Ecoflex silicone on the epoxy, just to be certain it doesn't inhibit the cure, but if that works I will probably go for it.
Tuesday, 09 November 2010 17:48
Well, if it helps the issue with the Mrs any, a small kit of Soma Foama goes a long way and it won't come anywhere near your home oven! :)
Tuesday, 09 November 2010 15:13