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creating molds and castings

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JimJ

Sun Oct 25 2020, 08:16pm

Registered Member #5746

Joined: Mon Aug 17 2020, 03:16am
Posts: 200

I have been making molds for casting for quite a number of years now and have found that most of the softer molds making material ( 1:1 mix ratio) really isn't worth working with. I have always used Alumalite 10:1 silicone type stuff. Have actually used some from various other manufacturers as well. The 10:1 silicones are a lot stiffer and remain flexible for part removal. I typically build a "box" out of legos with a piece of plastic sealed to the bottom with modeling clay for the mold "frame". Once the mold is set I can remove it from the lego box and have a nice solid mold. Mold release is an absoulte necessity when working with resins of all types. Some manufacturers make a thinner for the silicone should it get too thick when sitting on the shelf for a long period of time. I have used it on some silicone that had been sitting for almost 5 years and was so thick I didn't think I could use it at all, but it worked just fine - guess I was just lucky. I have a vibrating table made from a piece of ply with some dense rubber pads on the bottom and just use an aquarium air pump to vibrate it. It really does help remove the air bubbles when using slow cure resins. Haven't had the need to use this stuff for ship building yet but will probably be doing some soon. Have mostly been doing it for stuff like this: