I use NOVACAN BLACK Patina.. from the stained glass store...
The bottle says it contains nitric acid and selenium compounds
(What ever > they are) a little help, John Burgess from Down
You rang, modom? G’day; I’m not a great deal of help here, I’m
afraid. Except that all selenium compounds are extremely poisonous.
The element selenium is in may ways similar to sulphur, though not so
abundant in nature. It forms very similar compounds to those of
sulphur; for instance selenic acid is selenium trioxide dissolved in
water and analogous to sulphuric acid which is formed from sulphur
trioxide dissolved in water. Selenic acid forms salts called
selenates with metals, just as sulphuric acid forms metal sulphates
(e.g., copper sulphate and selenate). Selenides are similar to
sulphides (e.g… potassium sulphide, and selenide) You all know how
awful hydrogen sulphide smells? Rotten eggs. And it is also rather
poisonous. Well hydrogen selenide smells positively ghastly. Rotten
eggs plus rotten fish, plus rotten cabbage plus rotten garlic… and
very poisonous indeed.
Many of the compounds of selenium are black, and I suspect that
silver, copper, and lead selenides are harder than the sulphide -
though I am not too certain of that. Selenic acid and selenides are
part of the ingredients of ‘gun blueing’ solutions, but I don’t really
know exactly how they work.
One strange thing is that although selenium compounds are extremely
poisonous, traces of selenium are essential for many plants and
animals, and in certain places in NZ, sheep didn’t do well; their wool
was poor. Until tiny amounts of selenium were added to the top
dressing given to grass paddocks, and that sorted out that problem!
It all gets down to the definition of poison, just: TOO MUCH! Not a
whole lot of practical help, but I do my best. Modom. Cheers,
/\ John Burgess
/ / Johnb@ts.co.nz
(_______) It's springtime in Mapua Nelson NZ But today
it’s cold rainy and nasty.