Photopolymer plates with tabletop platen C&P
On more than several occassions the quality of my prints has been compromised because of this process. Please help me figure out why. The ink seems to “spread” out from the imprint and all line weights are much thicker, bolder and “muddier” than the original files.
I know it’s not my press, ink coverage or paper because the imprint looks beautiful when hit with lead type. The type on the last 2-color business card plate I had looked so poor I actually cut it off the plate and reset the entire card with actual type…leaving only a sub-par logo from the polymer.
I’m using a deep-relief base with KF 152 plates on a tabletop platen C&P press. Like I said, everything looks great so whatelse could it be?
Updated. Examine the plate to see if it is faithful to the negative and original art.
If it is, then your problem is either with inking or impression. Probably inking and probably due to your plate and base being more than type high .918”
Regular handset type prints well. It is .918. Visualize this same well printing type higher than .918. That increases roller pressure and applies ink on the shoulders of the letters and into the counters of the closed letters. Lower case e is usually the first to fill with ink. Now with inked shoulders and filled counters you will make a fuzzy impression. To demonstrate this, set a handset form and put two or three pieces of 20# stock behind the form when you put the chase in the press. Each sheet is about .003. You should notice reduced quality if your tympan was set right for the form without the extra height added to the type.
It is a bit difficult to measure the height of your poly plate form with plate attached to the base. With a micrometer, you can measure several spots around the perimeter and that might be enough. .918 is correct. You can’t lower it, but you can raise it. If you don’t have a micrometer, but do have some large type or type high rule and a good straight edge, you can get a measurement that will tell you if your form is over or under. If you have a couple of pieces of 72 pt type, put one on either side of the form on your stone and put the straight edge over the type pieces and form. If the straight edge rests on the form and not the type, you know what your problem is. If you use the type high rule, lock it in the chase and measure the same way.
If you are using only a poly plate and not type and plate mixed in the form, and if you have determined that your form is too high and you are getting poor inking, there is a work around.
You tape up the rails to raise the rollers to get the correct inking.
Poly plates are a mixed bag.
Tell us when you find what the problem is so others may learn. We need to teach one another to perpetuate this ancient craft.
inky
Julienne -
First thing to check is your packing. Make sure it’s fresh with no embossing - or spot makeready left over from the last job.
An easy test for the height of your photo polymer vs your.918” lead type is to simply remove packing on the press until your type fades away. If the photo polymer plate image continues to print, it’s likely higher than the type.
There may be some foreign matter between the plate and the base - or between the back of the plate and the press bed. Wipe all surfaces clean and look them over carefully.
Also - some older presses have ink/solvent or rust built up on the bed - and/or the platen. Although it’s not likely, since your type prints okay, it’s still a good idea to make sure that’s not the case on your press.
Another thing I would recommend is a very close look at your polymer plate using a loupe. Get in close so that you can see the face, the relief and the counter. The do the same with your type and see if the plate has the same sharpness as the type. It may be that the negative was not tight against the plate during exposure, which would leave a less-than-sharp image on the polymer.
A third possibility is a bowed lockup. If you are using old, worn furniture, or there is anything out of square in your lockup, you could bow the form so that the center area is raised. Although this would press back under impression, a bowed form would lead to heavier-than-wanted inking and would probably also give you a blurred image.
Last thing that comes to mind is the diameter of your roller trucks vs the rollers themselves, and the rolling action of the ink rollers as they cross the form. Make sure that the rollers are indeed rolling and not slipping at all. You may need to wrap tape around the trucks if the rollers are more than a few points larger in diameter.
Some rollers being sold for the Pilot do not have a perfect fit to the original C&P trucks, which can cause binding on the trucks against the saddle. Be sure that you can slip a piece of card stock between the trucks and the saddle to make sure that there is sufficent gap there and no side binding against the saddle.
Then again, you may simply have a bad plate. It can happen.
Let us know if any of our ideas are helpful. - AND what the answer is once you find it..
- Alan