I have been vacuum casting sterling silver for around 40 years.
Originally I designed all my projects so that I could remove fire
scale by wet sanding.
Around 20 years ago I stumbled on a process that eliminated fire
scale during vacuum casting. Its a very simple process that works. I
can now create3D items without fire scale.
Check the process out. I wrote two papers describing the process and
they are in Orchids "Tips From the Jewelers Bench"
The process works and will save on material cost.