Posted: 22 August 2008 at 9:23am | IP Logged | 1
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Molds? Heck, I've got 1-pc RTV, 1-pc latex, 2-pc RTV, and even 3-pc RTV. Depends on the part I'm casting. Heads work well with 1-pc molds, and anything that needs two defined sides needs a 2-pc. I use latex for when I need only a couple of copies of a piece, and RTV when I need several. There's probably as many methods for mold making as there are mold makers.
For mold boxes, it's hard to beat Legos or Lego knock-offs. They disassemble and reassemble easily and give consistent, repeatable shapes. The RTV peels right off of them, and I can configure them to pretty much any size I need.
Lessee, anything else Iearned the hard way? Lots.
1) Use Kleen Klay or identical brand to lay-up molds. Common kids modelling clay contains sulfur, which will inhibit the RTV's ability to cure. Makes for a gooey mess.
2) DON'T use the wooden craft sticks to stir the A and B resin mixture. Wood can trap moisture from the air and transfer it to the resin. Moisture makes resin foam. Makes for a foamy mess.
3) If you're making 2-part molds make sure you coat the first part with a rubber to rubber mold release before pouring the second part. You'll want to be able to remove your patterns from the cured mold.
4) Baby powder or talcum makes a good mold release when casting resin parts. It also breaks the surface tension of the liquid resin, allowing it to flow into the mold cavity better and reduce air bubbles.
5) Do NOT get this stuff on your hands. Not only does it become hard as a rock after it cures, it gives off heat (about 120 degrees, as I recall), and can burn. Use the latex gloves and lay down newspapers to prevent permanent additions to the dining room table and divorce attorney fees.
6) Don't be in too big a hurry to remove cast parts from the mold. Make sure you allow plenty of time for the resin to cure. Otherwise the parts will deform from the stress placed on them during de-molding.
There's probably more, but that's all I've got right now.
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