By Stephen Mc Millan
This etching technique creates gradual tonal change over an aquatint by allowing the acid to gradually "creep" across the plate. This produces an effect that is not possible when a plate is submerged in the acid all at once.
Stephen McMillan used creep-etch from time to time to achieve tonal changes in the skies of landscape images. Then in 1977, while working on a single plate image of a foggy orchard, he realized he would need to use a whole series of creep-etches to accomplish the desired range of tones. The technical challenges of his print, "Morning Fog", inspired the development of his personal system of creep-etching which he has developed over the years.
Before doing a creep-etch he first draws a diagram of the plate and uses it to work out the etch times of the creep-etch. The diagram, often with a rough sketch of the image, is drawn in pen, and using a pencil to draw in possible creep-etch times. He uses test plates and educated guesses to guide him in choosing the etch times.
When he has decided on the etch time progression, he draws a line beside an edge of the diagram that represents the edge of the plate. On this line representing the plate edge, he writes numbers to indicate when the acid should cross that part of the plate. These numbers are in the reverse order of the etch time numbers. For example, the point to be etched the longest is where the creep-etch will start, and is marked with a zero to indicate no time elapsed before the acid should arrive at that point. The area to be etched the shortest time will get the highest elapsed time number of the creep-etch since it indicates where the creep-etch ends.
Sometimes a plate will be removed from the acid and washed as soon as the creeping procedure is completed, but in many cases the plate is submerged entirely for a period of time after the creeping is finished. For example, a creep-etch of ten-to-sixty minutes would be totally submerged after fifty minutes and would come out in another ten minutes at sixty minutes.
The time at which the plate is to be removed from the acid is specified on every diagram as the "OUT" time. The "OUT" time is the total elapsed time on the stopwatch. If the plate comes out immediately after the creeping procedure, he writes "OUT" on the diagram beside the highest number in the creep-etch. If the plate is to be submerged completely for a time after the creeping procedure, the "OUT" number will be the time of the creep plus the time of total submersion.
Once the diagram is complete, the information needs to be applied to the plate. He does that by sticking tabs or strips of masking tape on the back of the plate so that they stick out from under the plate. On these tabs he writes numbers that correspond with the acid coverage times on the diagram.
As successive creep-etches are done over a plate, the cumulative etch times may vary a great deal from point to point on the plate. McMillan uses the creep-etch diagrams as records of the etches that have been done. To determine the cumulative etch time of a particular spot on a plate, he adds up all of the etch times over that spot as recorded in the diagrams. That number, plus any other etching done over that spot, is a close approximation of the actual time that spot has been etched in the acid. In designing a new creep-etch progression, he often adds up cumulative etch times for several spots on the plate and transfers them to a new diagram. These cumulative times are also useful in making an educated guess of what tones have been etched into the plate so far.
For some images he only wants to do a single creep-etch and then even out the etch times across the plate. To do this he does a "reverse creep-etch" which simply progresses in the opposite direction of the first creep-etch and thus evens out the etch times. Variations of this can be used to even out the etch times in darker areas after a series of creep-etches have been used for lighter tones.
DOING THE CREEP-ETCH
Since creep-etch requires that you spend extended periods very close to the acid, it is particularly important that you wear proper lung and eye protection and that the acid area have an effective fume removal system.
A basic creep-etch is just a matter of allowing the acid to gradually move over an aquatinted plate. I used to lower the plate into the acid by hand, which does work, but is hard to control and can get tiresome for longer etches. Therefore, McMillan uses a gradual acid submersion method that is much easier to control. This can be done by propping up the acid tray, so that it slants at about ten degrees from level. Next, a small pool of acid is poured into the low end of the tray, leaving enough room so that the plate can be set in the tray and still be completely out of the acid. It is important that the plate is dry. Acid will be pulled quickly into any damp area. Now the stage is set for the creep-etch to start.
The plate is pushed toward the acid until the acid is touching the zero point or line on the plate. When a creep-etch starts at the edge of a plate, carefully ease the plate into the acid until the acid climbs the beveled edge of the plate and begins to move onto the plate. At this point start the stopwatch. The zero line for some creep-etches, however, is located some distance in from the edge of the plate. In these cases, the plate is quickly slipped into the acid until the acid arrives at the zero line. Then the stopwatch is started and the creep-etch commences.
Example of Creep-Etch in Progress
The creep can be accomplished by either nudging the plate deeper into the tray or adding more acid to the tray. A combination can be used, pouring the acid from a glass measuring cup, and nudging the plate gradually farther into the tray with a small piece of wood, such as the handle of a brush. Depending on the speed of the creep you may have to nudge the plate frequently or may wait a minute or more between nudges.
A creep-etch requires constant or near-constant movement of the acid over the aquatint to achieve an even, unstreaked tone. This is particularly true for quicker passages over fine-grained aquatints.
By using the slanted tray method it is possible to make the acid move at a very slow but steady pace up the plate. With gradual pouring and/or incremental pushing of the plate, the leading edge of the acid will be a small wall moving very slowly up the plate. Sometimes the movement of the acid on the plate is so gradual that it can barely be seen, such as when it is only moving an inch every five minutes.
If the acid is too slow in reaching a specific area, it can be gently pushed into that area with a feather or brush. If the movement is too rapid the plate can be slightly pulled out and the acid carefully blown back. Clearly, you should be very careful if you try to blow the acid, and you should wear eye protection at all times. A major unwanted acid incursion may require a rapid removal and washing of the plate. If this happens, try to remember to stop the stopwatch (but don't zero it). After the plate is dry the creep can be resumed from the location where it was interrupted and the stopwatch started running again.
To lessen the chances of streaks, a single creep-etch can be done as a few shorter creep-etches. For example, a zero-to-sixty-minute creep could be done as three separate zero-to-twenty-minute creep-etches, thus evening out the variations of the creep-etches.
To do a creep-etch that does not travel as a straight line across the plate, the tray should be closer to level so that the acid can be feathered into the desired areas. When the tray is close to level, any unevenness in the plate is more likely to affect the progress of the creep-etch across the plate. For this reason it is advisable to make sure that a plate is reasonably flat before planning to do a creep-etch on it.
There may, however, be occasions when unevenness of a plate will be intentionally created to alter the way the acid advances over the plate. For example, setting small pieces of wood under a plate to gently bend part of it up and thus alter the progress of the creep-etch. This method is most effective for larger plates since small plates don't bend sufficiently. The closer the plate is to level, the easier it is to feather acid into nonlinear shapes on the plate. This creep-etch feathering technique resembles a process called spit bite, which is another way of creating detailed tonal variation. Spit biting is accomplished by gradually dripping acid onto a plate with an eye dropper, paint brush, or other tool.
Close attention must be paid to the stopwatch to keep the acid moving across the plate at the desired rate. After five minutes the acid should draw a line across the plate between the two tabs with the five-minute marks. If you plan to use a feather to move acid into certain areas it helps to have the diagram at hand to determine when and where. Once a creep-etch is started you are pretty much stuck there until it is done.