Thor,
where could I find more on this topic ammonia + peroxide for
etching, I use nitric acid ( very dangerous and toxic) mostly on
copper and brass and every thin in behalf of safer methods is
welcome.
Apparently you have misunderstood the thread’s topic. The original
poster wondered where she could find industrial strength (anhydrous)
ammonia, since she was under the impression that it could be used in
etching. The rest of the thread since then has branched off from
this, including mentioning the use of peroxide mixed with sodium
bisulphate (like Sparex) pickle as a supercharged pickle which will
lightly etch copper.
But the thread has been a little confusing.
The bottom line is that Ammonia is NOT normally used for etching,
either with, or without, peroxide. Anhydrous ammonia is sometimes
used in industry, such as in etching the copper on electronics
circuit boards, as Jim Binnion pointed out (which I hadn’t known.
thanks Jim), but be aware that anhydrous ammonia is an extremely
toxic and dangerous material, which can be safely used only with
proper ventilation and usually, industrial equipment. It’s not used
in jewelry work for etching. Ammonia does have some potential uses in
refining and in photography or the refining of silver containing
photo paper, since ammonia is able to dissolve silver chloride, which
is not generally soluble in water. But this does not have, so far as
I know, any application to etching for jewelry use. It is also used,
when dilute, as a cleaning agent, such as in many household
cleaners, and it can be used, again when dilute, in some methods of
putting blue or green patinas on various metals, especially copper,
bronze, and brass. As anyone who’s used it for cleaning knows, even
when very dilute like this, the odor can be noxious, and if used in
closed spaces without ventilation, even dilute ammonia has safety
issues.
As I noted above, hydrogen peroxide can be added to ordinary pickle
to make it more aggressive. The most common use is when people have
accidentally had some iron in contact with their silver when
pickling, which can leave a copper coating, or when brass is soldered
or annealed, which leaves it with a copper color instead of the brass
color. In both these situations, the peroxide/pickle mixture will
etch the copper enough to remove that, without damaging the silver.
With brass or actual copper, it does continue to attack the metal.
Whether this would be useful for actual etching, where some depth of
cut is desired, is questionable, but you could try it.
For safer alternatives to nitric acid for etching, you can use
ferric nitrate, an acid salt of nitric acid. This is actually a
preferred etchant for silver, since it cuts more smoothly with less
undercutting.
For etching copper, rather than nitric acid, you can use either
sulphuric acid, though this is not that much safer than nitric acid,
or more commonly, an acid salt of sulphuric acid, ferric sulphate.
This is a dark brown solution, which you can buy as a dry chemical
and mix with water, which makes shipping it much easier. It’s
commonly used in electronics as the etchant used to remove copper
from circuit boards, and can be obtained from electronics suppliers,
the sorts of companies that sell to hobbyists and experimenters who
wish to make their own circuit boards. Ferric sulphate does not have
the risks of really nasty fumes that sulphuric acid or nitric acid
does. It still is acidic, of course, and should still be used with
ventilation, and rubber gloves, but this would be expected. Either
way, it’s much safer and easier to use and store than are the
straight acids.
Hope that helps.
Peter Rowe