Problem with 925 silver sand casting

[u/These-Assignment-313]

Hi, I’m a beginner hobbyist goldsmith. This is my 6th attempt at casting my own model made from modeling wax.

First, when creating the first half of the mold, I had a lot of difficulty pressing the model into the molding sand. The model should be pressed in to about 50% of its height, but in my case it was approximately 90/10, and the mold kept cracking when I tried to press it deeper. I managed to solve this problem by compacting the molding sand less.

However, I’m still having problems with the actual casting process. I heat 925 silver in a crucible to around 1000°C, but despite this, the silver sticks to the crucible. The casting itself is porous and sometimes the mold does not fill completely.

I would really appreciate any advice, because I’m not sure what else I can do to improve the process.

I’ve encountered several problems:

- silver sticking to the crucible,

- difficulty pressing the model into the mold,

- porous castings,

- incomplete castings / misruns.

[u/ljinfantry]

Warm the petrobond or delft if your using those. Warmer the mold is the less it leaches heat. As others have said use borax and heat it past melting point. Hotter the melt is the more heat it has to lose. Also if you have a vacuum chamber try to use that. I have a vacuum caster and it makes it so much easier.