Cynthia, I would suggest electro-etching.
My set-up consists of a 12-volt rectifier (as used for charging car
batteries) and a series of 5 12-volt 1-watt (or thereabouts) bulbs.
These five bulbs are set in bulb holders wired in parallel to each
other, in one of the two output (i.e. dc) leads of the rectifier.
Basically, by removing / adding bulbs (by screwing them out of /
into their holders) you reduce / increase the amount of current
allowed to pass through the etching bath, and visual inspection of
the lit bulbs tells you immediately what that current is! This is
far more useful (and much cheaper) than an ammeter or similar gauge.
An in-built advantage is that you have complete protection against
accidental short-circuit, since the maximum current that can flow is
limited by the bulbs, which are of course designed for the full
voltage. One bulb in circuit means the maximum current is about 83ma
(volts x amps = watts). Five bulbs (in parallel) give a maximum
current of 5 times that, 415ma. The actual- current flowing will be
reduced from these figures by the resistance of the etching bath
itself, although one can normally arrange that that is quite low.
This method has been so simple and successful (sometimes four or
five times faster than chemical etching) that I rarely do etching
(of copper, steel, bronze, tin / pewter, silver) without it. A
related advantage is that you need minimal or no acid in the etching
bath, with the result that the resist is much less stressed. The
only time I bother adding any acid is if the conductivity of the
appropriate etching salt is not high enough in solution. In this
case I would add a drop or two of a suitable acid (nitric to ferric
nitrate, sulphuric to copper sulphate, hydrochloric or citric to
ferric chloride etc) until I am happy with the amount of current
that can flow (I’m the impatient type).
Electro-etching does not give exactly the same effect as simple
chemical etching; for one thing, metal for the most part is removed
only where there are electrical inducements to remove it, i.e.
straight-line conducting paths from the metal to the other electrode
(unless there is too much acid in the bath). I find this is a very
useful property, since chemical etching removes metal wherever there
are areas of the object to be etched exposed to the corrosive
etching solution. The etched profile is also sharper than with
chemical etching, being more vertical than U-shaped. I usually use a
bath consisting of a cylindrical plastic soup container filled with
the electrolyte and a stainless steel mesh acting as the negative
electrode, wrapped round the inside edge. The object to be etched is
suspended in the centre of the bath and connected to the positive
I hope I have not put anybody off the process of electro-etching
since it is actually very simple and low-tech.