Hello everyone, I know shrinkage is such an in-depth topic. I have been reading many posts and I’m so thankful for all the insight.

I’m looking for an answer in regards to shrinkage for
Brass and sterling silver
Is the shrinkage % for these two metals generally the same?
I have been running shrinkage tests in brass and creating molds with brass masters and now I’m concerned that if I cast in sterling silver I might have a different shrinkage percentage outcome.

Thank you for your help

Julia. I use VLT rubber for all my jewelry size molds, it has a very low shrinkage. It cures at 160F for about an hour. If you are injecting rubber molds with wax, you will also have shrinkage there, or if you use too much air pressure in your wax pot the items will get thicker. In the foundry industry it is common to make up “molders rulers” which are oversize metal rulers with the shrink built in. (brass is 3/16" per foot) Once you cast in silver you can go back and measure and make some kind of comparison notes. Brass reacts in natural rubber molds causing a less than smooth surface. Pewter is another model metal as long as you keep your pewter tools separate from your tools for silver and gold so as to prevent tin contamination. You can cast the pewter directly into silicone molds. I do that sometimes. I just make a rough design, cast it in pewter and refine it with files and chasing tools then remold. The VLT rubber is designed to mold carving wax. You can mold many other materials with it. Even if you do not have a vulcanizer you can use an oven and some c clamps.

Cheers Marty

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