MagicBob Posted January 23, 2004 Report Share Posted January 23, 2004 I tried the tutorial on silicone clam molds, and I keep getting little bubbles on the inside of the mold that of course show up as holes in the molded part. I have a couple of thoughts about what it might be, but I'm not sure about either of them. One is that I used too much water in the silicone mix and its boiling out making bubbles when I pour hot plastic. The other is that because the piece I'm casting is kinda thick (1/2") maybe there's a heat buildup causing bubbles. Any ideas????? Quote Link to comment Share on other sites More sharing options...
Fish_N_Fool Posted January 24, 2004 Report Share Posted January 24, 2004 Is there bubbles in the mold it's self? or just in the bait? If you can't see any bubble pockets in the mold then your are either getting a void from shrinkage, or you don't have a vent hole in the right place to let the air out of the mold so I gets traped inside. If you can see a hole in the mold just fill it with a little silicone. Hope that helps. Quote Link to comment Share on other sites More sharing options...
redg8r Posted January 24, 2004 Report Share Posted January 24, 2004 Hi Bob, It may be both Its tricky getting all the bublles out of such a thick material, but stirring slowly will help. Adding a layer of silicone straight to the master before you submerge it will help isolate bubbles also. once they're in there & close to the mold surface, heat will cause them to expand & make "female" indentions on the bait. If you can find em & fill em it might be salvageble as is, but if not, you can always cut up the mold & use it as "filler" for your next try. good luck Quote Link to comment Share on other sites More sharing options...
MagicBob Posted January 25, 2004 Author Report Share Posted January 25, 2004 Thanks. The bubbles are small (1/16" or less) and appeared after the first couple of pours. I'm leaning toward too much water mixed with the silicone. I used a few tablespoons (not measured) for half a tube. Is that too much??? I guess I may have stirred a little too fast too. Quote Link to comment Share on other sites More sharing options...
redg8r Posted January 25, 2004 Report Share Posted January 25, 2004 a couple (2) tablespoons should be right for about 5 ounces of silicone (half tube) I should really look into standardizing the ratio, but unfortunately the special effects forum where Riverman & I found this technique is no longer online so I cant contact anyone more knowledgable, so its trial & error until we get it figured out. feel free to post your findings as you come across em. thanks Quote Link to comment Share on other sites More sharing options...
Husky Posted March 16, 2004 Report Share Posted March 16, 2004 Which Brand Silicone do you all use? I've tried GE 100% Silicone and it never gets to a hardened state. How hard does your silicone cure to? TIA, Mike. Quote Link to comment Share on other sites More sharing options...
nova Posted March 16, 2004 Report Share Posted March 16, 2004 I had the same problem with the GE; wouldn't harden up. Are you whipping the silicone or just stiring it gently. After it starts to get a little thicker take a putty knife and flatten the silicone out. This will help break the bubbles you made from stirring it. I tried something a little different. I buttered up the blank about 1/2" on all sides except the bottom; let it harden up. Then I set it in an alum. pan and poured plaster over top. When it came out I had an open silicone mold encased in plaster.(if you drop it, you just pour more plaster) it works just great. Quote Link to comment Share on other sites More sharing options...
