An acquaintance has shown me a quantity (apparently several ounces)
of silver "powder", apparently recovered from some photographic
processing operation several years back. Has anyone ever dealt with
this stuff before?
G’day; shops and firms which do photographic processing on a fairly
large scale use sodium or ammonium thiosulphate - and lately other
chemicals - to ‘fix’ the image, and this dissolves unused silver from
negatives and photographs. There are a number of methods of
recovering this waste silver which over a year or so can amount to a
considerable amount of money. Concentration is necessary, but to heat
and evaporate the waste is expensive, and other methods are used.
Deionising columns are often used to concentrate silver ions then
treating the columns with other chemicals can release the
concentrated silver salts, which can be reduced to silver by
electrolysis, and this method would result in fairly pure silver
- Can I just melt it down in a crucible and pour an ingot? Any idea
of the purity?
to arrive at a decisive figure for purity the silver would have to
undergo assay by a competent laboratory
- Any residual chemicals or toxic elements I need to be aware of?
Without complete knowledge of the recycling of the silver in
question, the answer can be no more than a guess, but I personally
believe it should be free from toxic substances.
- Something best sent to legitimate refiner?
Silver is a relatively cheap metal and refining and assay are
expensive. It could be that sending it to a refiner might not turn
out to save much money relative to the cost of silver from an
I personally would be inclined to melt a small quantity and cast a
rod ingot around 5mm diameter, then use that to make thin wire. Very
careful examination of the wire and it’s annealed properties would
expose ‘jags’ due to unwanted alloying elements. In the words of the
prophet, suck it and see! However, if one were to make jewellery with
this metal, it would be unethical to quality stamp it without assay.
John Burgess; @John_Burgess2 of Mapua Nelson NZ