As mentioned on the "Recipes" page, this oxidizer only works on copper
while the oxygen is being released by the ferric chloride catalyst.
The solution can be reactivated by adding a small amount of
Hydrogen Peroxide to the spent solution. Even as little as a
tablespoon of fresh hydrogen peroxide added to a gallon of spent
solution will reactivate it for an hour or so. Since you end
up
with water and ferric chloride why not start out with water and ferric
chloride and add a small amount of peroxide to it when you want to use
it? You can, but you get a better looking patina/oxidation if
you
start out with a quantity of hydrogen peroxide and let it bubble all
day and then rejuvenate it for subsequent use by adding small
quantities of fresh hydrogen peroxide. Theoretically, the
ferric
chloride is only a catalyst so should not need to be replaced, but
adding a drop or two to the solution at infrequent intervals will make
it more agressive.
Transferring imagery for multiple plates, sometimes referred to as
"counter-proofing" is a process of etching imagery on a "key" plate,
then printing that on to a piece of paper, then replacing the key plate
with a blank second plate, laying the freshly printed image on the
second plate and running it back through the press to transfer some of
the wet ink from the "proof" on to the blank second plate.
This
transferred ink acts as a resist, so when you put the "counterproofed"
plate in the oxidizer only the uninked areas are darkened by oxidation
and the areas covered by any trace of ink stay shiny, so the imagery
shows up clearly. This oxidation is unaffected by heat,
solvents
and grounds. When etching on the plate is completed, the oxidation can
be easily removed with Brasso. This imagery is usually
clearly
visible under aquatints, but sometimes when it is used for
step-biting and an area is deeply bitten it can become hard to
see, since the discoloration is eaten away under the rosin along with
the copper. Lines transferred by overlays with transfer paper
to
the topside of the rosin can be used to deal with this. The
best
detailed description of this process I've seen is the Stephen McMillan
article at Multiple Plate Aquatint.
It is also very useful as an indicator of where etching will occur,
without actually etching the plate. If you have just cooked a
rosin aquatint and want to check it to make sure it will etch freely
when placed in the acid you can place a drop of the oxidizer somewhere
on the plate, wait 10 to 30 seconds, and rinse it off and dry the
plate. If you see a patch where the drop of oxidizer was, it will etch.
If you leave it on for 10 seconds and when you rinse it off
(or
blot it with a paper towel) you see a strong patch, it will etch
freely. If you leave it on for 30
seconds and
there is a very faint patch, slow etching will happen. If
there
is blockage, the oxidizer will rinse off and leave no trace.
Similarly you can do this to see if etching is happening in
some
questionable area of a plate. When you etch the plate the
oxidation will be removed.