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APMM Vendor Member Reynolds Advanced Material Mold Max 60 might work--I've done very limited testing with pewter pours. I'm not sure it would work well for bulky parts that hold the heat longer since you are right up against the temp limit of the material with your pour temp.
RTV is going to be an expensive approach. I'm paying $15 to $20 for a 9 x1 inch black rubber set (FRESH series 700 from Contenti--it begins to harden after 6 to 12 months). A full 9 x 1 with poured silicone would be many times that cost.
Why not instead pull a standard silicone mold and then cast off a vulcanizable model in either Reynolds 321/326, or better still, cast it up in Reynolds Task-2.
Make sure your vulcanizer is well calibrated, which in my case meant replacing the heating elements. I cold pack, because I don't want to lift a heavy and hot frame. Slide the packed frame in and bring down the platens to just touch the frame lids. Preheat 13 minutes (1-inch frame) and then apply pressure. I burp it after 5 minutes, but that need is debatable. Then go firm pressure at 300 degrees for 1-1/2 hours.
If you want to try preserve the model, allow the mold to cool. The materials swell slightly under heat and they lock in to the mold. Its really hard to open a cold mold and I am not a patient person, so I usually just plan on cracking the model, but the cavity is always good.
Using this technique, you will find about 1% expansion vs. traditional 3% to 8% shrink in your mold cavity.
David--ask more questions here, or call me anytime! |
