Electrical tape will work, but works better if your pieces are flat
and without any other texture (reticulation, for example). Buttercut,
a resist used by glass workers for sandblasting, is heavier and
rubbery and will conform to textures and curves better. If you have a
lot of curves or recesses (like a carved ring shank), my favorite is
UHU. UHU is a brand of removable adhesive putty, commonly used to
stick posters on the wall, stuff like that. I use it to cover stones,
to cover omega clips, masking off highly carved rings, etc. Peels
right off, and is reusable. I'm sure other brands of adhesive putty
will work as well, but I like saying " UHU."
Zaruba & Co.
35 N. Market St.
Frederick, MD 21701