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.
www.ganoksin.com/borisat/nenam/safe-etching.htm (article by Gail
Nelson)
www.LapidaryJournal.com
(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
Archives, too)
All the best,
Judy Bjorkman
Ferric Chloride will etch brass, nickel silver, and copper. If
possible, hang the metal upside down or lay on the green kitchen
scrubby mesh. This helps to keep the sludge from staying on the
metal and slowing the etch. You can get a deep etch.
If using ferric chloride the piece should be suspended in the bath
upside down (i.e. the surface to be etch should be facing down).
Ferric chloride etches really well, but a sludge can build up in the
etched areas, slowing down the process. A student suggested to me
that we float the pieces taped to small pieces of styrofoam - it
works really well. You can also write the time you put it in the
solution to keep track of the time. We always keep a lid on the
solution to prevent evaporation. Many people try to agitate the
solution, as that seems to speed up the etching process (we use an
old bubbler from a fish tank under the container).
If you use Edinburgh etch - you can put the metal in the solution
with the image facing up - the sludge isn’t a problem with it.
In terms of tape - we use the brown packing tape - but clear will
work as well - it’s just more difficult to see exactly where it is.
We use it to tape onto the styrofoam pieces, to protect the back and
edges from etching and as a resist. By the way the styrofoam can be
used repeatedly - just wash them off and dry them. Dense styrofoam
(blue and pink) is better than the white.
Sandra