MORE ROSIN!
For many printmakers, getting a good aquatint has been an elusive and frustrating quest.
This article relates some of my experience with aquatint and is meant to help you get the results
you want with aquatint. It is written for the experienced etcher. It assumes knowledge of basic
etching procedures including plate preparation, studio safety, and intaglio printing.
Aquatints can produce a vast range of tonal values and textural effects in an etching. With
the knowledge of a few simple determining factors an artist can choose precisely what kind of
aquatint to use for the etching. The most important factors in creating an aquatint are: the amount
and grain size of rosin on the plate, the degree of melting of the rosin onto the plate, and the
amount of time the plate is acid-etched.
Probably the most common mistake made in attempting to do an aquatint is to put too
little rosin on the plate. To counter this it can be useful to put more rosin onto the plate than you
think is needed. It was through intentionally "over-rosining" that I found out about very dense,
and ultra dense aquatints, which I have used in a number of prints. Whether doing a hand
dropped, box dropped, or even spray can aquatint, it is vital that an adequate amount of the
surface of the plate be protected from the acid during the etch. Once too much of the surface has
been etched away it is very difficult to repair the damage short of scraping, burnishing and
starting over. It is therefore crucial that enough rosin get on the plate. My own rule of thumb is
to drop at least enough rosin onto the plate to obscure the metal when viewed from about 30
degrees up from the plate. For fine-grained rosin the coverage should appear even heavier since
the grains are smaller and will spread out less when melted onto the plate.
Another important consideration in dropping rosin onto the plate is the size of the
individual grains of rosin. Some rosins are pre-ground and will have nothing but fine grains.
These rosins are excellent for fine-grained aquatints but can be problematical for coarser ones.
Hand-ground lump rosin, whether used in an aquatint box or hand dropped, allows for a much
greater range of grain sizes. The variably sized grains of rosin will fall at different rates in a
box, thus giving you some control over what size of rosin will settle onto the plate. After the
rosin has been raised in the box, the larger, heavier rosin grains fall first, while the finer grains
float down much more slowly. To get coarser grains the plate is put onto the box soon after
the rosin is raised. If only larger rosin grains are wanted, the plate should be removed after
about a minute in the box. To get finer grains the plate should go into the box anywhere from
15 seconds to more than a minute after the rosin is raised, depending on how fine a rosin grain
is desired. Since much of the rosin will have dropped before the plate is in the box, the plate
may have to be put into the box a two or three times before there is enough rosin on it. In most
cases it is not necessary to try to isolate a narrow range of rosin grain sizes. I usually place a
plate in the box a few seconds after the dust is raised and then leave it in for at least 10 minutes.
Aquatint boxes vary quite a bit, so it is important to get a feel for the characteristics of the
particular box you are using. A good box should deposit enough rosin after one time in the
box, but unfortunately some require that two or more drops be done before heating the plate. If
a box does not deposit enough rosin it is also possible that the box needs more rosin to be
ground and added to it. Some boxes require more vigorous cranking than others and so may
just need more strength from you. If you are working with an unfamiliar box it is advisable to
do a few test aquatints to get a sense of how that one works. I have learned a lot through doing
test plates. In a relatively short period of time you can try many rosining and heating variations,
while developing a feel for the process.
DIAGRAM OF ROSIN MELTED ONTO THE PLATE
Once the rosin is on the plate, heat is applied to melt it onto the plate. The amount of heat
and rate of application determine how the rosin will melt. Enough heat must be applied to at
least melt the grains until they are hemispheres stuck onto the plate. Under-heated rosin will
not adhere to the plate well and will therefore not protect enough of the plate. When lump rosin
melts the first thing to look for is the change from dry amber-colored dust into wet transparent
dots. It is easiest to see this transition happening by viewing the plate from a very low angle.
A small magnifying lens is a useful tool in seeing how the melting is progressing, particularly
with a fine-grained aquatint. It takes a bit of practice to find the best angle and lighting to see
the rosin on the plate. I use the hand lens on a Swiss Army knife. A geologist's 10X hand lens
or a jeweler's loupe also works well. For the fine-grained aquatints the plate should be heated
gradually, with only enough to just melt the grains onto the plate.
There are a few ways to heat a plate. The most common is a hot plate. Set the hot plate
at about 200 to 250 to melt fine grain lump rosin onto a plate. Different rosins melt at different
temperatures, so you may need to experiment. Place the rosined plate onto a sheet, or several
sheets, of paper on the hot plate. I use about four layers of heavy paper bag type paper. This
will help avoid hot spots and will make it easier to move the plate when needed. The rosin may
not melt evenly, so be ready to move and gently tip the plate to get the heat were you want it.
Uneven heating can be a real problem with larger plates, especially if they are larger than the
hot plate. If available, a gas flame wand works well for larger plates. There must also be a
raised screen of some sort to set the plate on while the flame is moved under it. Another
alternative to a gas flame is an alcohol soaked cotton ball in a frying pan. Be sure to have a
tight fitting lid to extinguish the flame! When using a gas flame wand or alcohol to heat the
plate, particular care must be taken to gradually heat the plate if a fine grained aquatint is
desired. This method can melt rosin so fast that the small grains melt together. As more heat is
applied, the grains spread, becoming larger and covering more of the metal. The resulting
aquatint is grainier and denser. If you start with larger grains on the plate they will tend to
spread out more than the fine grains. In either case, the addition of heat will cause the rosin to
continue to spread, coalesce, and cover more metal. It is possible to overheat the rosin and
totally cover the plate. The smoother the surface of a plate, the less likely it is that an aquatint
will totally cover it. Conversely, on a rougher plate, such as a previously etched aquatint, it is
much easier to over melt the rosin. A rougher surface tends to draw the liquid rosin out while a
polished surface will hold it at bay. It is surprising how much rosin and heat can be applied to
a plate without totally over-melting it. To produce a very dense highly textual aquatint I use a
gas flame wand to really fry a heavily rosined polished plate until it looks very wet and shiny,
and gives off smoke. I might not have found out how to do this if I had not tried to over-rosin
and overheat test plates. One caught fire and yet still produced an interesting aquatint!
After the rosin is in place the plate is ready to be acid etched. Copper is generally
etched in Dutch Mordant. The mixture I use is 25 parts water, five parts hydrochloric acid, one
part potassium chlorate crystals, and at least several parts old Dutch Mordant. If old acid is not
available a scrap of copper can be put into the acid for an hour or so. A common acid mixture
for zinc is 12 parts water to one part nitric acid. 12 to one nitric etches zinc about three to four
times faster than Dutch Mordant etches copper. The etch times needed to create a full tonal range
over an aquatint depends on the grain size of the aquatint, and the percent of metal exposed.
A very fine-grained aquatint could over-etch after only 10 minutes in Dutch Mordant while a
very dense aquatint could be etched 10 hours. The smaller the grain of an aquatint, the faster
the acid will etch under the rosin. Even though Dutch Mordant tends to etch down it still will
undercut the rosin given enough time. As the grain size increases so does the maximum etch
time possible. The percent of metal covered also makes a large difference. Light coverage will
over-etch quickly while heavy coverage can be etched much longer. A very dense aquatint can
be etched for several hours in Dutch mordant, and yet still leave enough original surface
remaining for another aquatint to be dropped onto. At the lighter end of the scale, a very
fine-grained, medium dense aquatint may need to be etched only 10 seconds to produce a light
tone while a coarse grain, very dense aquatint may need 10 minutes for a light tone. Given the
large variation of etch time in relation to tone produced it is advisable to make test plates to help
in determining what etch time produces what tone over a particular grain and density of aquatint.
The temperature of the acid will effect the etch speed, so that should be taken into
account if the temperature in the studio changes much. Longer times may be needed when
using colder acid, and shorter times for that hot summer day. I have not done any quantitative
tests with acid temperature, but would guess that etch times change by a factor of about two
every 10 to 15 degrees Celsius. This is only a guess. In Summer my acid is about 21 degrees,
and in winter it gets down to about 14 degrees. In Winter I generally etch about one half time
longer.
Between etches the plate should be examined with a hand lens. The lens is particularly
useful in determining how close the aquatint is to being etched to the maximum depth, short of
over etching, and ruining the plate. It is very important to maintain visual contact with the
aquatint, both when putting it onto the plate and when etching it into the plate. Much of your
success with aquatint depends on knowing what looks right. As you develop your skills with
aquatint you will learn what to look for, both with the lens and with unaided eyes.
Generally an aquatint is used to create a number of tones on the plate. A stop out
material is used to paint out areas of the plate between etches, usually starting with a paint-out
before any etching is done and progressing tone by tone to a dark, deeply etched tone. I have
always used asphaltum thinned some with kerosene or mineral spirits as the stop-out, though
there are a number of other stop-out materials available.
Another way to achieve a tonal range is to etch an entire plate to a black tone and then
use a burnisher to draw in the lighter tones. One advantage of this is that the pre-etched plate
can be worked on far from the studio, even in the wilderness. A burnished aquatint can be
proofed at any time during the drawing process since the rosin and acid have already done their
job. Although the resultant print will look somewhat like a mezzotint it does have a distinct
quality of its own. Some prints done this way are: Easy Chair, Lake of the Woods, Leaf Rhythms,
and Reflections and Carp.
An additional way to get a tonal range is to do a creep etch, which is done by allowing
the acid to gradually move up the surface of the aquatinted plate. For short creep etches the
plate can be gradually lowered into the acid. For longer creep etches the acid tray is blocked up
to a gradual slope, the plate placed on the slope, and then acid is slowly poured into the tray.
A long creep over a very dense aquatint can last well over an hour. I go into more detail on this
in my article, "Creep Etch".
Sometimes several aquatints are needed to create the desired image on the plate. As long
as enough of the original surface remains after the previous etches, a plate can be re-aquatinted
and re-etched. Use a hand lens to inspect the areas to be re-etched. If less than 20 percent of the
original surface remains, an additional aquatint is very likely to over-etch quickly. Only 20
percent is already on the fragile side. With 40 percent or more the plate should hold up to
further etching.
The re-rosining should cover the plate well, though not always as heavily as the first.
The etched-in texture already on the plate causes the rosin to spread out faster when it is heated,
making it easier to over-melt the rosin on the plate. The etched-in texture also makes it more
difficult to see how well the new aquatint is melting, and if it is adequately covering the plate.
This will definitely test your hand lens skills. Another possible problem is that on a variably
etched plate the rosin may spread out at different rates over different textures. That is, it may
be sparse on un-etched areas, but rather dense over well etched areas. This is much more likely
to be a problem with a second aquatint over a fine grain aquatint because the finer texture will
make the rosin spread more that a coarser one will. Generally when doing multiple aquatints
the coarser grained aquatints are done first, and the finer ones last. This way the smaller grains
of the fine grain aquatint rest on top of the larger "mesas" left by the previously etched coarse
aquatint. Additional aquatints are usually etched much less than the first one, both because of
the smaller grain size, and because less of the original surface remains to be etched. An image
can be gradually built up, using a number of aquatints, and other etching techniques. The only
limit is your imagination and patience. Always remember to wear your industrial dust and acid
fume masks when you work with these noxious chemicals!
Stephen McMillan © 1993 (revised 2000)
