Hi guys, for the last week I have been playing with some RTV silicone, I am really impressed with the detail it has and how easy it is to make molds with it. the problem I am having is that even after 3 coats of it its still flimsy it is. What are you guys using for backing. I also went to the auto parts store and picked up some PE and mat glass. the PE is what i believe they use to fix boats and stuff. its amber in color. i like the way that makes molds too but i get bubbles so ill try degassing it. what would be the best to use? the PE glass or a Silicone forl molds?
When building silicone molds, we build up 3/8" to 1/2" thick “glove” molds that then have a hard mother mold backer. For the mother mold we use pasti-paste which is a thick slurry of resin and chopped glass. The glass filled bondo would work just as well. When brushing on silicone molds always start with a very thin print coat; this keeps any bubbles out of your finish.
ok i will try that. is the bond between bondo and silicone perminate? and does the bondo shrink?
Im still in the experimenting stage and im still wondering if the PE/glass is better or worse?
The mother mold will not bond to the silicone (nothing really bonds to silicone), this is why silicone mold can sometimes be removed like a glove. The glass fill in some bondo reduces the shrinkage. What to use as a mold material really depends on what you are trying to mold.
oh ok that makes sense. Thank you Mattman! Im trying to mold things like side mirrors, mirror deletes, canards and hopefully get into Front lips. am i better off with the PE/glass or the silicone?