R.R., there have a number of Orchid discussions on this subject.
Here are my opinions.
For brass, ferric chloride does very, very nicely. It will etch as
much as you want it to. It is available in handy bottles at
RadioShack. It will not etch silver -- for that you need ferric
nitrate, available only at chemical specialty places.
To do both at once, you would need dilute (50:50) nitric acid. But
it is hard to find and nastier to work with. With ferric chloride, be
sure to wear rubber gloves -- it stains, among other things.
I would bet that the catalogue pickle solution is sodium bisulphate,
the same chemical as is your pool acid (Ph Minus). Neither this, nor
citric acid, are strong enough to etch satisfactorily (although, if
you leave something in your pickle long enough, it will very slowly
begin to etch and can be destroyed over a period of several hours).
However, the citric acid is sometimes recommended to add to the
ferric chloride to improve the etch on base metal.
See some of the following sites for more info.
(article by Gail
(look for articles by Katherine Palochak on low-tech photoetching,
where there will be some discussion of the
use of ferric chloride; look up Katherine's name in the the Orchid
All the best,