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Ferric chloride in etching


#1

Since the subject of etching with ferric chloride is under
discussion, here’s a tip to speed up the process.

If you can get hold of a magnetic stirrer such as chemists use, you
can about double the speed if etching, and keep the results clean
and smooth. A little magnet is enclosed in a plastic capsule, and
that is dropped into the bottom of your container (a round dish
works best). I cut the bottom inch off of a deli container, and
drilled many holes in the flat bottom. Then I cut what were the
sides so that only 4 or 5 small strips were left: picture a plastic
"table" with holes on it, with several short, thin legs to hold it
up over the encapsulated magnet. The work piece sits on that. The
dish sits on the stirrer, which is a black box with another magnet
just below the surface. A knob controls the rate of spin of that
magnet, and, as a result, the one in the bottom of your container.
So, when you fill with mordant, and gently turn on the
machine:voila! Wordy to describe, a snap to use. If you make enough
holes, you can effectively etch both sides, if you want to.

This woks a lot better than when I tried a vibrating table
intended for debubbling investment. The vibration set up a standing
wave, that sprouted into a fountain rising out of the niddle of the
bowl, sprinklind mordant in a 6 or 8" circular area. What a mess!

Noel


#2

Noel, I was always taught that you must suspend the piece you are
etching with the side to be etched facing down so the particles fall
away during the etching process. Are you saying that with the
magnetic stirrer you can etch the side facing up?

Deb


#3
  Noel, I was always taught that you must suspend the piece you
are etching with the side to be etched facing down so the particles
fall away during the etching process. Are you saying that with the
magnetic stirrer you can etch the side facing up? 

Hi, Deb, With silver, there are no particles, so you can always etch
it facing up. But with the magnetic stirrer, you can do both sides
easily–and evenly. With copper and brass, I’m not sure, but I think
it likely that the sludge would be swept away by the “current” on
top. But, truthfully, at the moment I can’t be sure I’ve actually
done that. Most of my etching is in silver. If you like, I’ll try it
and get back to you.

Noel


#4

Here is an interesting variation on the use of ferric chloride as
an etching mordant:

http://www.polymetaal.nl/beguin/mape/edinburgh_etch.htm

The paper is very complete so implementation will be simple.

This is a relatively recent addition used for printmaking plates in
zinc , copper or steel.

It uses a citric acid additive as a chelating agent. Citric acid
has long been used as for this purpose in industrial metal cleaning
agents that also include corrosion product removal. The process is
sound technically. I haven’t tried it yet but have some citric acid
on order. Maybe next week.

This suggests the use of EDTA ( also a food and medical use approved
chemical) as well , but citric acid is cheap, safe and relatively
easy to buy.

Jesse


#5
    I haven't tried it yet but have some citric acid on order. 
Maybe next week. 

Citric acid can be obtained through various local suppliers: In the
food canning section of the grocery store, a health food store, and
in various chain stores selling soap making supplies. The soap making
suppliers are usually the cheapest, as the citric doesn’t have to be
of food grade quality.