N_Cook wrote in message
...
I happen to have some potassium dichromate (not chromate) around, but a
solution of that on freshly scored lead sheet shows no obvious colour
change
to the lead surface.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



I tried some potassium dichromate, dissolved in some hot water, allowed to
cool and then placed in a small plastic lid. 3 samples , some scrapings of
lead sheet, some scrapings of silver solder and some lead-free solder
scrapings. Allowed to soak for three hours, towelled up the liquid and
allowed to dry out overnight. The only samples with any yellow colouring
were the lead ones, but I cannot convince myself it was not just a coating
of fine crystals of orange K dichromate, too thin to see the orange colour.
the lead-free scrapings were as silvery as when pared off.



--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/