The same substance in less pure forms occurs in commerce, as stick lac,
lump lac, seed lac, button lac.
Shellac Varnish.
Solution of shellac in alcohol; methylic alcohol (wood alcohol or wood
naphtha) is often used as solvent.
Dr. Muirhead recommends button lac, dissolved in absolute alcohol, and
the top layers decanted. For highest insulation he dissolves the lac in
ordinary alcohol, precipitates by dropping into water, collects the
precipitate, dries and dissolves in absolute alcohol.
Shielded. adj.
An electric measuring instrument of the galvanometer type is shielded
when it is so constructed that its indications are not seriously
affected by the presence of neighboring magnets or by fields of force.
Shielding can be effected by using a very strong permanent magnet to
produce a field within which the magnetic needle moves and which reacts
upon it, or by enclosing the instrument in a thick iron box.