Photogravure: Single-Acid Etch
Photogravure: a photographic print made on an intaglio press from a hand-inked copper plate.
Photogravure is tricky because there are so many ways to screw up the process before you finally get to the ink, the paper, and the printing press. If it were easy, more people would be using the intaglio press to print photographic material because the final results can be so sublime.
From the tonality controls in the digital positive, to the image transfer via gelatin tissue onto the copper plate, and finally to the inking of the plate and its ultimate printed impression on paper, each phase of the work demands know-how, attention, patience and vision.
Etching the positive image into the copper plate (where it becomes a negative) has always been difficult to get right (while there are many different ways to succeed). The etch requires special conditions of temperature and humidity to be consistent, and it also takes judgement in terms of reading the values of the etch in the copper - during the etch - to yield the desired intentions of shadow and highlight in the final image.
A Significantly Shorter and Simplified Process
The single-acid etch was discovered by accident during a workshop demonstration. We had an extra gelatin step tablet laying around and decided to print it quickly, thinking it would register a nice reference for the endeavors of the afternoon. Instead of controlling the humidity and waiting hours for the gelatin to dry on the plate, we placed the copper plate and gelatin on a hot plate to dry. After 25 minutes the plate was cooled to room temperature and placed in one ferric-chloride etching bath. Without any further attention, he resulting etch was tonally excellent.
I was surprised it worked so well and have been using this method with fairly consistent results ever since. If a film positive and tissue are prepared in advance, it can take less than two hours to process a photogravure plate. This process was achieved using an Epson printer and Dragon gravure tissue. It is a simple outline, however, please note that there is a considerable amount of key information unstated between the steps:
Create a film profile limited to a maximum density of 1.4.
Print a digital 21-Step tablet on your film of choice.
Sensitize the Dragon tissue in a 4% potassium dichromate solution chilled to 45 degrees for 75 seconds.
Use equal tone and aquatint exposures.
Degrease the copper plate.
Place the degreased copper plate in distilled water, chilled to 45 degrees.
Slide the exposed tissue, face side up, into the tray with the copper.
Flip the tissue over and position it over the copper. Remove the copper and tissue from the bath at a gentle angle. I use a thick glass sheet positioned on an overturned tray in my my sink as a surface for laminating the gelatin tissue and the copper together. The surface on which you squeegee should be close to the temperature of your mating bath.
Blot the backing paper and wait 75 seconds.
Immerse the plate into 115 degree development water. Wait two minutes before peeling the tissue.
After 4-8 minutes of minutes of agitation and hosing the clearing is complete.
Place the plate in a tray bath containing a 50% solution of isopropyl alcohol for 2 minutes. Remove the plate from the alcohol and flood with 75% isopropyl. Agitate the plate in hand. Flood the plate twice within 45 seconds.
Dry the plate as evenly as you can. Rock the plate and watch the alcohol closely. Modify your technique to make the alcohol evaporate as evenly as possible.
Allow the plate to rest with good air circulation for twenty minutes.
Mask the plate.
After 25 minutes drying, place the plate on a hot plate heated to 120°F for 25 minutes.
After 25 minutes, move the plate to a room-temperature surface.
As soon as the plate has cooled to room temperature, etch in 40.3 ferric chloride.
Proof.
Create a profile. Make plates. Make prints.
Review the photogravure reference page for trouble shooting and more information.
Tips:
Room temperature means, like, 68°F to 72°F; consistency is the objective.
Look closely at everything.
If you have problems, run through the entire process with very bright lights on.
Use a head magnifier.
If something is not working properly, repeating what you did exactly will not make it work.
Experiment. Read. Study. Do not believe everything you read.
Don’t sneak up on things. Test and test again.