Sterling silver melting & pouring

Hello to everyone.

I need some about sterling silver melting and pouring in
an investment casting process (gypsum moulds), in order to cast

I’ve been using aluminium alloys for industrial purposes and now I
have to cast sterling silver. I’m completely new in this field. I
made a couple of trials with this procedure, as first approach:

  • a button and a central sprue (10 mm x 3 mm diameter) for each ring
    (2 cylinders).

  • SiC crucible, electric oven

  • metal pouring at 980 C in a vacuum machine

  • mold temperature 500 C

I noticed a considerable amount of shrinkage: castings showed a
partial filling, due to an incorrect solidification (I obtained only
the lower part of the rings, those connected to the sprue). I think
I’m not accostumed to work with this material and I obviously made a
mistake (or more…).

Any suggestion is welcome.
Thank you very much.