Inking issue on windmill redball 10x15

What do you use to wash up with?

Have you checked the plate under magnifying glass?
Or very basic, checked the platen packing for damage.
I must admit I’m one of the old school printers brought up on kiss impression and am amazed at the detail I can hold using good quality coated stock and polymer plates.

Hi there,

Did you manage to sort this problem out? I am having the same problem on my Heidelberg.

thanks
much appreciated

I recently had a problem where inking was poor and inconsistent roughly in the middle of the plate area. Everything looked fine with the plate. What I eventually discovered was that small amounts of oil were being thrown from the gripper apparatus onto the middle area of the rollers and mixing imperceptibly with the ink, causing it to not adhere to the plate (I had just done the weekly oiling). Now I’m very careful to thoroughly wipe down everything on that part of the press before printing and haven’t had the problem reoccur since then. Maybe this could be the simple solution to your issue?

Dear Sylvia,

Thank you for your sharing. That sounds very likely! I also suspected this issue as I had recently asked the operator to oil more religiously, following the red and yellow indicators.

Plus we also use some offset cleaning solution (unsure of the name) to clean our polymer plates off the cotton residue of the paper after every 30-50pcs of print. Our cotton paper comes with a lot of cotton particles that sometimes coat on the polymer plate.

I will try to clean up any possible oil spots from the machine and see how it goes. Update here again!

Thank you.

Dear Theo, we usually wash up with the usual offset cleaning solution. Understand that isnt the most ideal but we dont have many options in Indonesia.

Dear Frank, we only use usual woodfree paper for packing and change them before every print. Is that okay?

If you have a look at the Heidelberg handbook you will see that you can vary the packing, I tend to have at least one sheet of thin card and sometimes 2 sheets for a harder packing.

I might throw out the radical idea that the plate is fine, the inking satisfactory, paper probably right on, and platen/impression setting acceptable. What is missing is makeready and proper packing. Deep impression letterpress in soft paper is best done with hard packing, not soft, cushion like packing. The idea is to compress the paper fibers in the sheet of paper, not push the type through the paper until it is popping out the back of the sheet.

Next is makeready. Plates tend to punch the sheet on the ends of lines and be weaker in the middle as shown in this example. And makeready, the dreaded 9 letter word is the solution to this. Back off on the platen pressure until the end of the line prints as needed, then add makeready to the rest of the line to bring it up to proper impression. This requires working under the top sheet or tympan on the platen of the press adding tissue sheets to the areas printing too weak until the line prints cleanly. Makeready is a necessary evil in letterpress and is poorly understood by most press people—crank on the impression and add ink is often the usual solution. I am prompted to mention all this after catching this ad from DuPont in the October 1963 issue of the Inland Printer—and by way of explanation, Dycril was the pioneer photopolymer plate material introduced in the early 1960s—and those plates needed some makeready then as now. See https://flic.kr/p/22BcGrC

and the ad gives a pretty good idea of how the makeready might have been marked up on the printed sheet by the press person before starting the patching up of the sheet.

Yes Nagraph, makeready is possibly a forgotten art. As a letterpress book printer in years gone by makeready was done by putting maybe 2 sheets through the press and patching up the top sheet from the back relying on looking at the impression show through. I have just produced a 4 colour post card on my VM last week having spent time first making 3 sheet overlays. Almost unheard off these days.