Ink, rollers, tack?

Does anyone have a solution for the mini-dots phenomenon on the photo attached? I’ve been unable to work out if it’s a humidity issue (we’re air-conditioned), an ink issue (in this case, we’re using rubber-based Van Son black straight from the can), or something else. We’re printing from a polymer plate, and this happens on all kinds of papers, not just the cotton rag stock shown.

We have just adjusted the roller height.

I see this problem when printing both on the Vandercook and the C&P which would lead me to believe that it’s not a roller issue since one set is rubber and the other is composition.

With fine-lined designs, this isn’t noticeable at all, but with any kind of larger or solid areas (the image is only about half an inch wide) it happens frequently.

Any thoughts would be most appreciated.


image: printdetail.jpg


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Shelly…. I’m not a fan of rubber-based ink, but you should be able to get it to print a solid image. It looks like a texture/impression pressure problem to me.

Try dampening a few sheets of paper, and see how they print. If they print ok, then you aren’t getting enough pressure to print the dry paper…. either the press is too light, or the plate is compressing a little, or the tympan/packing is too soft. ( a too soft tympan is a common culprit.)

If dampening the paper fails to improve the image, then it is an ink problem after all.

I have the same issue also, and have discovered it to be the texture of the paper itself. print it on a smooth finish and it will be more solid, use a linen finish an dthe linen weave may show through. Next time you print solid try it on several different paper finishes with the same press settings and you will see the differance each paper produces.