I’m not new to jewelry making but new to casting. I need to make molds for lost wax casting from sterling silver master models. My models are not overly complex (no filigree or deep undercuts) but have very fine surface texture that needs to be reproduced as faithfully as possible.
Let’s assume that neither shrinkage nor shelf life matter, with detail being the primary focus – what mold material is going to do this best?
So far I tried yellow RTV silicone and the result was satisfactory overall, although the level of detail in the cast piece shows just a touch less detail than the master model (which I figure is to be expected?).
Is there anything better for this application? Natural rubber, blue rubber, Castaldo VLT, …?
Silicone rubber will pick up extremely fine surface detail, which will transfer to a wax model faithfully. Some of this can be lost in the casting process, but details as fine as a fingerprint can be successfully reproduced using lost-wax investment casting. Other casting techniques, like sand-casting (aka Delft clay) will yield lesser amounts of detail due to their coarseness. And it’s also possible to lose detail in castings through metal shrinkage, if there’s insufficient hot metal in reserve to feed the casting as it cools. I don’t think any other rubber will give you better reproduction of fine surface features, although some will stretch better without tearing.
Thank you @awerby for answering! When you say silicone rubber, would that be RTV (room temperature vulcanization), or silicone that cures at high temperature, i.e. requiring processing in a vulcanizer? Do you know if there are any differences between those two types with regard to detail reproduction? Or is the difference between those types mostly in the durability/shelf life of the mold?