I produce limited edition woodcuts on a 15KA Challenge Proof press and in the middle of a run for some reason the ‘top’ element on the block registers with image on the sheet and the ‘lower’ element on the block is printing 3/16th if an inch off register (lower on the sheet). The distance between elements on the block is 3 1/2″ and print 3 11/16″ apart on the sheet. HELP!
To start, ‘Thank You’ Paul, Eric, Kyle & John for your prompt help
identifying the problem and suggested solutions. I’m self taught so with
your clues and upon closer observation this is what I’ve come up with.
The paper is stiff (Reisling Stonehenge Cover), the press sheet is 7″x10″,
grain short, gripped on the 7, the image is 3 1/2″x6″. My first impression
ran fine, there being no gaps in the block. Trouble started trying to plug
in the other elements. As I observed, pressure between the gripper and the
tail of the sheet in contact with the ‘paper straps’ creates a bow (paper
is too stiff to sag) in the sheet that falls between the two elements
creating the off register.
I immediately tried Kyles suggestion of running 5 pica furniture down each
side of the block and it was an improvement but I could still see a slight
bow in the sheet. A test confirmed I was still a little out of register so
I started thinking about taping the tail of the sheet to keep it tight to
Reading John’s recommendation I made a 7″x24″ test frisket (I use a press
sheet size frisket anyway) and sans ink found it to hold the sheet tight
to the cylinder but awkward retrieving the print by reaching under the
feed table as I ordinarily do. BUT, on tripping the cylinder and reversing
the direction while holding the end of the frisket as I back it out, the
paper is stiff enough to miss hitting the side guide and delivers nicely
onto the feed table.
Unfortunately I injured my thumb the same weekend after my troubles
registering began so didn’t actually ink up to resume my run until
yesterday. The long frisket worked like a charm. Registration was dead on
and delivery convenient. I believe I will print with a long frisket from
here on out.
Another ploy which could work is to print on a longer sheet, registered to the guides, and cut out the printing areas. Then, when placing the stock to be printed, add the mask sheet (actually a frisket) over the top. This gives you a means to hold the smaller sheet tight against the cylinder throughout the impression, keeping the middle of the sheet from sagging.
While it seems that this would add a good deal to the printing process, it actually is easier than taping the tail of each sheet to the cylinder. It serves the same purpose as the frisket tower on some other proof presses.
Eric is right – this is probably paper-sag between the two printed elements. It is crazy that it’s happening in such a short span. It’s usually a bigger issue on long sheets, stiff paper, and anytime you’re printing against the grain (when the paper doesn’t want to bend with the cylinder).
Eric’s solution of locking a block in place works well. Sometimes we use a Boxcar base in the middle space to help keep the paper from sagging too far. A mounted linoleum block might do the trick also (straight from the art supply store they are just a little under type-high.
For you, with such a small space in-between, I’d fill the gap with some 5-pica furniture, turned on its side so that it stands tall.This is a smidge under type-high, and should hold the sheet up, tighter to the cylinder. If your furniture is as dirty as some of ours is, just lay some masking tape over it for a clean surface. Eric’s idea of screws would work well also, as would taping some leading flat onto the gap in-between.
Finally, if none of this works, or can’t be done for whatever reason, I have used a loop of tape stuck trick many times. This holds the printed sheet taut to the tympan. We place it right where the tail of the printed sheet ends, and then use more tape to hold the sticky loop down. The drawbacks here are that 1.) You have to pick it off carefully with each print. 2.) The tape can tear the printed sheet a little. And 3.) The tape wears out and needs to be replaced sometimes. But, it works quite well. Just smooth the printed sheet over the tape loop with each pass, and it should remain tight to the cylinder for the length of the press bed, keeping tight registration. Be sure to place the tape away from printed areas so that you avoid printing over the tape loop.
The other issue you may find is that you can resolve this color’s registration issues, but that your first printed elements also bounced around the page and so registration is still difficult.
Hopefully you close up that 3/16″ gap!
3/16″ is a huge difference over such a short span. I can get 6-12 points difference in print length (over 23″) if there is a large gap in the form and the sheet sags between isolated head and tail elements. My usual solution is to raise the surface of the blank areas of the form, to maybe six points below inking; if you have one continuous woodblock you could insert screws which can be adjusted to a suitable height. You can also tape the tail of the sheet to the cylinder but that has its limits. Holding the tail against the cylinder should be normal practice but again it has its limits on longer and heavier sheets.