Polymer Plates & Their Finicky Printing.

Over the last few weeks, I’ve used two photopolymer plates from Boxcar Press to print. I’ve experienced with both of them that they don’t ink fully without adjustment. I have a Boxcar Base, and each time I have to pull the plate off the base, add some layers of tape underneath the problem areas, and then take out some packing from my setup. Does this happen to everyone else? Is this normal? It’s mostly just inconvenient and not really a detrimental issue, but I was hoping to confirm that I wasn’t doing something catastrophically wrong.

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Well, how accurate is your equipment?
I’m not questioning your skill set, but I’m asking about the condition of your equipment and how new/flat/true etc your rollers are.

In my experience, photopolymer is more accurate than the equipment is in some cases. Rollers being worn wouldn’t show up with normal height type or even metal cuts, as you can add a bit of pressure.
Photopolymer is within a stricter, tighter tolerance than most other forms you can print with. Even swelling at the edges of rollers (which is actually wear at the middle!) can be an issue if you’re, for example, printing all the way at the ‘edge’ of the press.

My rollers are brand new, and this is with an adjustment of roller height.

Things you may consider…
I wouldn’t rule out the rollers, I’ve gotten bad NEW rollers.
If your not using regular press wash, the incorrect chemical can ruin them. Making them swell unevenly.
If you leave them parked over the ink disc, that little bit of pressure can leave a flat spot, especially if you use something to wash them up, that is not good for them.
Lots of trial and error.

Were I troubleshooting this, a problem with the plate would be toward the bottom of my list. I assume you are working on your C&P and have the new rollers on the press. Roller adjustment, uneven tape on the trucks or bearers, truck slippage and bearer wear would be further up the list to investigate. Solvent on the plate or even the temperature and/or humidity in your workspace could be a contributor.

Boxcar make very good plates. I have seen an occasional defect, but have seen probably over a thousand of their plates come through here. The few defects I have seen were visible with the naked eye and typically visible on the proof enclosed with the plate shipment.


Thanks everyone! I have a feeling it probably has to do with inconsistencies in roller height if nothing else. Although my own shop is new, I worked as an apprentice of a letterpress printer who has been in operation for 25 years, and know about simple things like to always leave your rollers at the bottom and never over your ink disk. I don’t use press wash due to the chemicals, but that’s not something I feel I need to debate.

The Arm NYC; This is good to know! Usually this happens the first time I use the plate, and then I can adjust tape under the plate/roller trucks to compensate. I don’t *actually* know how to adjust the roller height on my C&P, another thing that might help in this situation. It has been pretty humid in Seattle lately, but not enough to effect the plates (I don’t think). I think the rollers and their trucks are probably the answer. Thanks for all your advice!

A good place to start to learn about roller adjustment is right here on Boxcar’s webpage.


Best of luck with your printing.