Greetings Orchid, Some observations of mine. Sometime ago I made up
several ounces of niello using the Heinrich formula in Robert Von
Neumann's book "The Design and Creation of Jewelry".
The bad part of the process was in adding the sulfur powder to the
mix. Talk about stink. Had sulfur in my hair and moustache and
everywhere else too. Keep the wind to your back. Buy the sulfur at the
local plant nursery at a fraction of the chemical house price.
The difficulty, for me, was in using the niello. No matter how I
tried, it bubbled and therefore had holes that needed refilling. It
got on surfaces where I did not want it and required constant filing
and repolishing. It runs very readily and is not too easy to remove
especially down inside some delicate jewelry features.
I gave some to my teacher, mentor and friend and don't use it. He told
me of an instructor at California State University, Long Beach who
pours the molten niello into stick form rather like a pencil lead and
torches it into place that way(?) rather that grinding it into powder
which is a bit like enameling.
Most of the jewelry I have seen from the Far East that uses it seems
to be shallow etched and filled such that filing flat and removing
the excess is not too difficult. I had tried to fill a flat bezelled
table on a ring with a 20 g ornament soldered inside the setting. The
idea being that when polishing down the niello the ornament and
surrounding bezel would be seen against the grayish niello. Had
niello everywhere. Not aware of a niello stop. Never tried
'whiteout'. Once fired it is a pretty tough surface to remove. Bill in