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Sulfides & sulfates


In his book, Carles Codina says to use potassium sulfate for
blackening (‘oxidizing’) silver?

See The Complete Book of Jewelry Making by Carles Codina, pag. 83:

"… Potassium sulfate is the most common, made by dissolving 30 g
of sulfate in 1 liter of hot water… "

I ask: has somebody ever used POTASSIUM SULFATE for blackening
(‘oxidizing’) silver?

Best regards
G. Moura
Recife, Brazil

   blackening ('oxidizing') silver? 

G’day; Sulfates (sulphates) Do not, either in theory or in
practice, blacken silver. In any case, The blackening of silver by
the use of sulphides is not oxidation, (other than in a very
academic sense which doesn’t concern us here) but the conversion of
the surface of the silver into silver sulphide which is black.
Silver oxide is not black, but an off-white colour, and is difficult
to produce. Sterling silver, because it contains copper, does
blacken on heating in air due to the formation of copper oxides,
which can be removed by weak acids, such as sodium or potassium
bisulphAte, not sulphIde or sulphiTe So I am afraid I disagree with
Carles Codina. as quoted; but perhaps the truth was lost in a
translation? –

Cheers for now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ