Unknown Splotches Showing Up

Hi Folks,

I have a print I’ve been troubleshooting and here is what I’ve done so far with a little success, but now it seems I’m seeing some strange splotches when the ink overprints. I’m printing a lino cut on 80 lb cotton.

I recently put new delrin trucks on the rollers and it has helped the crispness from the test I did last week with old trucks. I removed some ink and that has helped keep ink from creeping over the sides. I have a heater next to the ink plate to keep the temp a little warmer (not certain if I’m for sure at 70 degress though).

My first pic is printing great, but when I overprint onto my final splotches show up. Here’s a photo to assess.

Thanks for your help! Katie

image: overprint.jpg


image: overprint2.jpg


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Any chance you’re overprinting oil-based ink onto wet rubber-based ink (or vice versa)?

Or maybe you just need to let your first color dry longer.

Thought maybe it might be something with the ink combination, but the 3 colors underneath are dry. Both oil based. I used quite a bit of transparent medium with first 3 and this last color is heavier on the pigment. Don’t know if that may make it hard to stick?

Which color is getting all blotchy? Is it the white? I’ve had trouble overprinting opaque white before and had to make sure the other colors were completely dry.

Does it blotch right away on press or as it dries?

So I cleaned my block and noticed some ink building up in certain areas…anyone know why?

image: 20151012_150059-1-1.jpg


OK, it looks like your colors are light pink, dark pink, light blue and red. You don’t say what order you are putting them down, except that the red is last. You are having trouble with the red trapping over (trapping means where one ink layer prints over another ink layer) the other colors. The red looks to me like it is trapping worst over the dark pink.

As a quick fix for this job, why don’t you try printing the red first and the other colors over it. Your other colors look pretty light and transparent, so the job probably won’t look much different if you print the red first. And, since the red is darker, if the other colors don’t trap well over the red, it may not be noticeable.

One thing to remember: inks adhere better to the paper than they do to other inks, so if the job will permit it, try not to put down colors with the most coverage (of the paper) first, forcing you to print more of the other colors over ink.

A couple of other things which can affect trapping:

Ink makers often add wax to the inks. This is not what you normally think of as candle wax, but usually finely powdered polyethylene wax. What the wax does is migrate through the ink film to the top surface as the ink dries, forming a very thin film of wax on the top of the ink. The purpose of the wax is to make the ink more rub resistant, so it will be harder to rub color off the surface. When the surface is rubbed, you are rubbing the slippery wax film and the color is protected. The only problem with this is that other inks don’t always stick well to the wax layer, and this can cause trapping problems.

Another factor in trapping, comes into play if you print multiple layers of ink which are not completely dry. This factor is called ink “tack.” Tack can be loosely defined as the stickiness of the ink. The first ink layer you put down should have the highest tack (should be the stickiest). The next ink layer you put down should be less sticky, so the stickier ink you printed first will pull the less sticky ink off the plate and onto the paper, and so on. Conversely, if your first ink is less sticky and your second ink is more sticky, then the ink will, to varying degrees, tend to pull ink off the paper (or off a previously printed ink layer), and back onto the plate.

A lot to think about…..

Thanks Geoffrey for all that advice…super helpful. Unfortunately I have already printed my transparent colors so would have to start all over again :0( However your tips will be awesome for future projects!

I’m hoping that it may just be an issue of the lino cut getting some kind of residue on it (the pic above shows some weird build up). I’m going to give it a good clean and start again tomorrow. I’ll report back

Thanks so much! Katie