All, We used a procedure to blacken sterling that lasted longer than
any other procedure I have ever used. It was as follows:
Complete all soldering and grinding.
Place the piece in battery acid until all the gunk is removed.
The piece should come out of the acid looking matte white. Rinse in
water.
Polish the piece to finish polish. Clean the piece with ammonia
and water.
Heat the piece on a hot plate to 200 degrees F. Heat a solution
of liver of sulfur and water to 200 degrees F. We used about two
cups of water to two 1/2 inch chunks of liver of sulfur.
Pick up the piece with tweezers and drop it into the hot liver
of sulfur. Leave the piece in the sulfur for at least 10 minutes.
Remove the piece and wash it in water. Dry the piece.
Prepolish the piece again on a cotton buff, not polishing away
the areas you want to stay darkened. Set your stones.
Finish polish the piece on a clean cotton buff. Clean the piece
with ammonia and water.
This seems like a lot of work, but I have pieces that are worn most
everyday for the last 20 years that are still black.
the process involving heated liver of sulfur is great, and it works
best for anything i have tried, but the heated liver of sulfur, i
have heard, makes cyanide, so i always do this under a hood, hold my
breath, or do it at an arms length. le tme know if anyone can
verify this, or dicount it, i would love to know!
Liver of Sulfur is Potassium Sulfide. Nothing you do to it can make
cyanide. Because of its offensive odor, it is a good idea to use it
under a hood or with GOOD ventilation. NEVER, NEVER, NEVER add acid to
Liver of Sulfur because it will produce Hydrogen Sulfide (H2S), which
is a VERY poisonous gas…Bob Williams
the process involving heated liver of sulfur is great, and it works
best for anything i have tried, but the heated liver of sulfur, i
have heard, makes cyanide,
G’day Brittany. Liver of sulphur is potassium polysulphide.
Cyanide contains carbon and nitrogen atoms. So it is quite impossible
for cyanide to be produced from liver of sulphur. However, the smell
of rotten eggs is caused by hydrogen sulphide being produced from
potassium (or calcium) polysulphides, and hydrogen sulphide gas is
as poisonous as carbon monoxide (from car exhausts, for instance) so
don’t add acid to the liquid. The amount of hydrogen sulphide
inhaled inadvertently from sulphiding metals won’t do much harm -
unless you are doing an awful lot. Just take care. – Cheers for now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ
Brittany, Liver of sulphur (potassium sulfide) when heated d=
oes
not change into cyanide, the chemicals involved are completly
different from each other. Liver of sulphur is benign in and of
itself, even when heated; the odor you get (rotten eggs) is from
sulphur dioxide formed by its reaction with the oxygen in the air and
is also benign. When you mix liver of sulphur with any acid
(accidently or otherwise) you release hydrogen sulfide gas ( H2S,
colorless and flammable) which is highly toxic and is rated as a
poison on the same level as cyanide. Both interfere with oxygen usage
on the level of the cells in your body (cellular hypoxia). It takes
a more severe exposure to H2S to produce the effects you hear about
coming from cyanide but it can be just as deadly.
Just some notes from a jeweler who was previously in the med=
ical
feild with a bent towards chemistry. (College electives convinced me
to change my goals away from Bio/Pre-Vet to studio arts).
10 minutes? geez, we find that less than 10 seconds is sufficient.
to get it black we burnish w/ brass brush, steel shot tumbler or mag
pin finisher. true it doesn’t last 20 years, less than 10 in fact,
but by that time the piece is in need of refinishing anyhow.
Sulphur dioxide is not produced by heating liver of sulphur - a
chemically complex salt - a metastable mixture of potassium
polysulfides and sulfate (K2S, K2S2, K2S3, K2S4, K2S5, K2SO4).
Hydrogen sulphide (H2S) is the gas that smells of rottn eggs.
Sulphur dioxide (SO2)has a different smell - its forms an acid when
it dissolves in water - which is why so many of us get wheezy when we
drink cheap white wines that have been preserved with sulphur
dioxide.
Heating liver of sulphur - or dropping it in acid will produce
hydrogen sulphide in large qualntities.
In concentrations of 150 or greater mg/kg (air), a person’s ability
to detect the gas is affected by temporary paralysis of the
olefactory nerves in the nose. Owing to this unique property of
Hydrogen sulphide, relying totally on the sense of smell to warn
against the gas, can be extremely dangerous. In high concentrations,
the ability to smell the gas is lost instantaneously, the
disappearance of the odour could mean that the gas concentrations
have increased.