Polymer Plate Printing Question

I use polymer plates with a Kelsey 5x8 and have this issue sometimes. Check that the platen is adjusted correctly. If it is, there are a couple things that could help..

The first thing I would try is just add a strip of packing only where it seems to be lighter. This usually fixes the issue for me.

If it’s an inking issue, I have put a thin strip of packing behind my polymer base on the light side. This helps if there is a variance in the polymer base from one side to the other.
You can also try to adjust your rails with some strapping tape, putting less on tape on the side that prints lighter.

Hope that helps.

This is very helpful—thank your for these suggestions. The impression seems close enough that I am loath to adjust the platen for fear of making things worse rather than better. I tried adjusting packing with thin tissue, but it maybe was not quite enough. I did not think of adding tape to the rail on the darkest side to adjust inking pressure.
Thanks again!

Another consideration is that the the total coverage area of the block looks to me to be uneven - the left side looks to have a bit more image area than the right. Thus requiring more ink applied on the left. With a rotating ink disc there is no good way to correct that, but one thing to try might be to place the block off center to the right as an experiment. If the off-center print area is not the issue, an adjustable fountain would be the solution on a cylinder press but would not work on your press. Careful hand inking MIGHT.

Bob

Sorry, double post due to slow system.

Bob

Try rotating the plate. If the Onondaga Lake side is still light, the plate is probably the problem. If the Eastwood side is light then it’s probably a press and/or roller issue.

Thank you, Bob and Sharecropper Press for these helpful suggestions. I will give it another try during the next few days and you have given me some great tips. I hope to give an update soon.
Thanks again!
Joe

geojoe -

Have you tried printing the card stock without dampening?

Michael

Michael, I tried a couple of dry test prints right after inking the disk, and the coverage was not as solid as I wished. In fairness though, I should try again since the disk was possibly still “under-inked”

After dampening the postcard stock and printing, they curl somewhat, so I put them in a finishing press to flatten them again.

Thanks for your question.
Joe

Update:
I used an inside caliper to check the platen adjustment and it seems very close (maybe even spot-on) from side to side and top to bottom. I rotated the form 180 degrees with no real difference. So, I began experimenting with packing and when I increased it on one area, another area became lighter (I tried several variations of this).

As a result, I have become convinced that my variation is more in the inking than in platen adjustment or packing. There is a bit of pitting in one spot near the edge of the ink disk but the ink does eventually cover the disk evenly. I just have to cycle the rollers many times until the even coverage occurs.

In summary, I ended up adding one layer of packing and used a bit more ink and the results seem improved (to my eyes, anyway). Example attached.

Joe

Syr Neigh bp.jpg