Vandercook inking problem
I’m printing a very large plate of a linear illustration. The poster size is 18x24 and the plate is almost that size. I’m using a Vandercook SP-20. The problem I’m having is, right in the middle of the form, I’m not getting solid ink coverage. It’s almost exactly in the center. My rollers are only 4 years old, although I suppose it’s possible they have shrunk a little. To get the middle to ink properly, I’ve had to really lower the rollers. The problem with that is then the ink coverage is so heavy on all 4 sides that it looks like crap and is slurring off and building up on the edges. Not good. I’m not sure what to do. The illustration is all connected lines, so I can’t pull out a piece and print in a second pass.
To make matters more fun, I’m running a 3-color split fountain. I was thinking of running the colors separately. Would they blend properly? The issue would still remain with the very center of the poster, as the middle color is very heavy on the leading and end of the sheet, but too light in the very middle. I just don’t know how to compensate for this. It doesn’t seem as if makeready on the packing would solve it as impression is fine.
I should also add that I can’t just pull up the plate and add some paper behind that section. It’s mounted on a wood board. If I pull it up, tons of little pieces of the wood come with it and that’d be it for the plate.
Help!
Have you tried putting a straight edge across the rollers to see if you can tell whether they are low in the middle? With each roller, try laying a strip of tissue or light paper in the middle and on both ends of the roller, then hold the straight edge on top of the roller with the strips on it, and then see if you can pull the middle strip out more easily than the end strips.
Have you checked them with a lollypop roller height gauge (the bead would be narrower in the middle if they were low there). If they are, maybe you can send them to a roller company and have them grind a tiny bit off so they are even.
As a stop-gap measure, could you perhaps ink the light place with a brayer, or does the split fountain keep you from doing that.
What about double or triple rolling the form?
I really don’t understand what you mean that you can’t pull up your plate as its mounted on wood. Its possible that your plate is not perfectly level or is low in the middle because of the wooden base? you can check that similar to how you check to see if the rollers have flat spot - pull a straight edge across the plate - might put a flashlight behind the straight edge it to see if more light shows through where you are having a problem.
It sounds like you’ve mounted the plate to a particle board base by your description (pulling the plate up would also pull up shards of wood)? If that’s the case, it’s likely the base height is not perfectly uniform. I mount my linoleum cuts to MDF/particle board and find that there are often low spots.
I’ve had success with slowly building up underlay under the base.