I do some rollerprinting and a lot of etching. Hopefully a few
of my tricks will help.
Different metals, different patinas–some patinas hold up better
than others. You didn’t mention what metal, only liver of sulfur.
Tell us the metal and if you need the lustre depth of the liver
of sulfur for more accurate answers.
If you just need to darken the lines in order to provide
contrast rather than lustre depth, you can take the easy way and
use black laquer. To remove the top surface on the highlights of
the metal, use a soft cloth with the appropriate solvent. Wrap
the cloth around a stick which will prevent it from removing the
laquer from the depressed areas.
Another way is to use finishing bars which are used in salons
for finishing acrylic and natural fingernails. These are
rectangular foam or flat boards with abrasive material on the
surface. They come in all grits from 60 to about 6000. Because of
the construction, they ride the top surface without going into
the depressions. The foam have a little more give than the
boards. They’re worthwhile tools to have in your workshop in any
event. They will also give various grades of satin finishes, the
foam bars can be used while wet, and will provide a high polish
in the finest grits. They also last a long time and are an
economical investment. A big plus is no grease to remove.
Hope it helps. K.P.