Ink Made especially for letterpress

OK so here’s the deal.

I find that when i use ink formulated for Offset, ie left over or intentionally ordered colors, i have trouble matching PMS because the ink film inherent to letterpress is too thick.

Offset ink is matched to be printed at a film thickness of 5 microns. Letterpress equipment can only get to about 15 micron thick ink film thickness, thus the color always comes out too dark.

I have a connection at a ink manufacturer and i had them formulate a bunch of PMS colors with a reduced pigment load so that the resulting film of 15 microns would have the same amount of pigment as the 5 micron offset film.

Would there be any interest in PMS inks made this way to offer to the letterpress community??

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Quite possibly. I think the question would be, are they willing to produce and sell in small quantities? I know I’d never need to buy a 5 Lb can of any ink. Making them available in 1 Lb cans would probably be a necessity.

Another question would be, what will this do to ink consistency? Having less pigment in proportion means having more medium/additives/dryers in proportion. What kind of ink thickness and flow on-press are we talking about? What about drying times?

It’s an interesting project, though. Thanks!

Michael Hurley
Titivilus Press
Memphis, TN

Or you could learn to adjust the color mix so it matches the swatch. You do realize the difference in microns you are talking about is 0.00039370 of an inch - an almost inconsequential difference. I’ve been mixing inks for letterpress for over thirty years and mixing for offset ten years prior to that, and have never run into the problems mixing from a PMS book that are continually mentioned on this list.

I would suggest that reducing the pigment load would cause a host of problems which would essentially make it harder to get the color intended. It would be much harder to keep up the color with any variance in the amount of ink being applied on the press, and since most letterpress printing is short-run work this would be a real problem. Also, how does one gauge the reduction in pigment to make up for the 10 micron coverage with which you are concerned? And how would this translate on paper if one is running 12pt lead type or 12 line wood type?

If you wanted to reduce the pigment load it would be easy enough to do by adding a small amount of transparent white, but then you would have to be willing to basically throw-out the PMS book and re-invent an ink-mixing formula that has worked very well for decades.

With ink there is no “one-size-fits-all”. Each press, from a hand-press to an high-speed cylinder takes a different kind of ink for optimal operation, and the color coverage varies with each press, as should the ink chemistry.


There are two types of “tones” which printing inks can give, the print tone and the mass tone. The print tone appears when the ink is transparent or semi-transparent, and the ink forms a colored filter on the sheet. The light goes through the ink film, is reflected off the sheet, and goes back through the ink film to the viewer’s eye. The mass tone is where the ink film is opaque, either because there is a lot of opaque white in it or because so much ink is put down that the light can’t get through it to the paper. In this case, the light is only reflected off the ink film.

OK, now let me throw this out:

When you achieve a print tone (with TRANSPARENT white in the formula if called for), the amount of ink used will cause the color to vary because you are making your colored filter (the ink film) lighter or darker by using more or less ink.

When you achieve a mass tone with opaque white, in theory the color should remain the same regardless of how much ink you apply (assuming a minimum ink film to achieve opacity), because the light is only bouncing off the top surface of the ink film, and never forming a filter or letting the paper play a role. So in theory, even though the amonunt of ink put down may vary, it should be easier to maintain color consistency. Has that been the experience of the people who use opaque white in the place of transparent white in PMS formulas?

Perhaps because I was in the printing business all my life before retirement, I mix inks using transparent white, as specified by the PMS formulas, so I don’t have any experience with using opaque white in PMS formulas.

Should an ink company make inks with a lower percentage of colored pigment, or should I mix transparent white into my inks to reduce the color strength? Personally, I would rather mix trans white in, as needed, myself. That way, the strength is there beforehand, if I should happen to need it. If all my inks are weaker, and I need the strength, I have no way to get it.

One other point: just because an ink is colorless, it doesn’t mean there isn’t any pigment in it. There are transparent pigments (like clay) which can be added to change it’s consistency, reduce cost, etc.

One advantage of reduced strength inks would be that they should be cheaper, because pigment is the most expensive component in an ink (with the exception of clear pigments like clay), and reduced strength inks would have less pigment.

Variation in color strength is called tint. There are pigments that are naturally opaque, and others that are very transparent. Using transparent pigments in ink is how 4-color process is possible. Transparent white allows the light to go through the film of ink, but it basically drives the pigment molecules farther apart, which is why when transparent white is added to a color it will give it a washed-out look. Opaque white will lighten the tint of any color with which it is mixed. It also prevents the light from penetrating the surface of the ink, making the ink appear to lie on the surface of the paper. It can help to hide color changes that might occur from laying the ink onto a toned or colored paper. Think watercolor and gouache. It’s the same principle.

I’ve recommended this repeatedly, but the best education of how pigments work that one could get in a single volume is a book titled Blue and Yellow Don’t Make Green (or how to mix the color you really want - every time), by Michael Wilcox. I mixed ink by the PMS book for almost 30 years never fully understanding what it was that I was doing. Wilcox’s book helped me to understand why certain colors combined make other colors. He recommends a color mixing palette that is very similar to PMS color mixing, but explains why - something that few printers understand even though they work with color every day.

If a color mix is off just a little bit a printer needs to know how to alter the mix slightly (even with the given measurements it is easy to be off a little from a PMS mix). It takes a good eye, and a knowledge of pigments to make the little tweaks necessary. A color on inked type can look totally different from a solid inked with the same color because of the amount of light reflected to your eye from the surface of the paper.

There are many, many variables that can make the ink appear the wrong color. Trying to match a color under florescent light is nearly impossible, and when I am forced into that situation I will always check my color sample outdoors; you would be amazed at the difference between the two. Reducing the pigment may sound like an easy fix, but it isn’t.

The other factor in the lack of inks for letterpress is varying inking systems. Platen jobber, high-speed platen, high-speed cylinder, proof press, tabletop presses; all are letterpress but have different optimal body characteristics.
Pigment load and roller settings aren’t our only problems.

We printed a calendar for a Philadelphia ad agency for the Sprout TV network that utilized 10 colors. The agency did the design. We had the PMS colors mixed at Gans. They were probably ok for offset but turned out to be way too dark via letterpress. We ended up mixing about 50% opaque white in the ink to get them at least near the colors we wanted. I think you can see from the photos that the colors are still intense.

Just for addtional printing information the calendar was 13 pages, 600 copies, 3 colors on each page, printed on our Vandercook SP15 and 4. All together about 27,000 impressions.

We did a set of 7 holiday cards for House Industries a couple years ago and they are very, very picky about color. To get the right red we had the color mixed 2 levels lighter in the PMS book. We were printing on a Heidelberg windmill. We would run the cards through multiple times to let the ink build up to the right color. The worst case was 5 runs and the best case was 2. But the color was dead on over all of the cards.

image: eph-sprout-2011-370.jpg