I define a sticky plate as an etching plate that will not clean properly. In the case of the plate below, there was a patch of ink that did not want to be removed. It caused me a lot of problems until, eventually, I figured out what I was doing wrong.
After inking the plate, it was scrimmed normally and printed. That was when I noticed the blemishes in the centre of the print. This etching was done on new, buffed steel, so the only marks that should have transferred would be the etching itself, not the clouding.
Below is the first proof of the clouding plate.
I printed the plate again but this time the print was worse, proving that I wasn't necessarily scrimming poorly. I highlighted the area of concern on the paper, then set about fixing it.
Beginning a new print, I concentrated on scrimming the clouding area clean. To my surprise, the print proofed as shown below. The clouding was far worse. After showing my prints to my tutors, we drew the conclusion that I must have unknowingly used contaminated ground rollers.
Soft ground and hard ground are grounds made of Vaseline and bitumen. Soft ground has a higher proportion of Vaseline to bitumen in comparison to hard ground, which has more bitumen than Vaseline. In consequence, hard ground has a higher melting temperature than soft ground.
When applying either to a steel plate, the metal must be heated. At university, we use a large hot plate. Because of the different melting temperatures, both grounds have separate rollers for application. I used soft ground on this plate, so the soft ground roller must have been contaminated with hard ground.
After printing the picture below, it became obvious that the ink clouding was accumulative.
Rather than cleaning the plate with oil, I decided to find something more heavy duty to strip away what was attracting the ink. I used a turpentine soaked rag to strip the plate.
I then inked, scrimmed and printed the plate normally.
The print proofed with little detail because of the shallow bite of the plate. I didn't let the acid bite through the soft ground long enough.
By the time I got to this final print, I think I've got the plate figured out now. After inking, I lightly scrimmed over the etching, concentrating instead on cleaning the border of the plate. The result is the print above. It is not a a good print, due to the shallow bite of the plate. It is not a bad print for the plate though.