My first question is how did you make the projects you are
Fire scale will form on sterling if the metal is not protected
during soldering. There are several anti fire scale fluxes on the
market that will prevent fire scale from forming during soldering.
Some better than others.
There is even an anti fire scale flux you can create on your own. A
review of the Orchid Archives will lead you to the formula.
Before each solder step the metal should be totally coated with the
anti fire scale flux.
Fire scale is a sever problem on castings. Fire scale forms as long
as sterling is heated above about 100 degrees F. During casting
sterling is maintained above 1000 degrees for a long period of time.
Fire scale forms continually during that time.
There is a process listed in the Orchid Archives that will prevent
fire scale during vacuum casting.
THE BEST IDEA IS TO NOT LET FIRE SCALE FORM. Once fire scale forms
you can remove by a braiding it away with course polishing compounds
or abrasive wheels. Unfortunately they can remove design. There are
chemical processes for removing fire scale that I would not
If I can be of any additional help let me know.