Ink mixing mystery

Hello all!
I’ve recently started a job at a shop and I’ve been having trouble mixing to pms match. I’ve mixed inks before with success ( although I was perhaps more lenient with myself than a client would be)
We use digital scales to mix ink. I’ve followed the formula to a T for 2128 u and tried some of the more common advice on ink mixing. 50/50 trans and opaq. 1/3rd opaque in place of trans, 90/10 trans and opaq. None of these have landed close enough. The former pressmen mixed by eye and only used opaque white, but they’re no longer here and it seems like their results were not always the best anyways. Our ink supplier seems to be Van Son but I’m not sure. A part of me suspects it may be a labeling issue as the shop has house names for colors and maybe things got shuffled up.
Any advice or pointers would be great.

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What I did in a case like that, I try mixing as cmyk formula.
Been mixing ink pms, metricolor and cmyk and never had a color rejected by a customer ( commercial printer btw for 43 years) don’t forget letterpress always prints darker, no fountain solutions to thin/lighten colors.
Hope this helps!

Have the ink mixed for you. That color will be hard to do. I have had Gans mix my inks for many years and never had a problem. Gans makes a letterpress snow white opaque ink. Not sure how they would use it to match a PMS color. Transparent white is hard to work with partly due the lack of pigment. Once pressed into the sheet it is all but gone.

Two possible options. Skip feed the sheet to a better amount of ink on the plate. Feed it through the press twice or even three times. First pass light ink light hit ( like a primer coat), second pass more ink more pressure and so on.

Here are a few ink mixing guidelines:

Ink makers say that a color is “clean” if it is pure and brilliant (like fire engine red or Kelly green), and “dirty” if it is dull and grayish (like slate blue or brown).

First draw a color wheel. Draw a circle, then divide it into 6 parts, starting from the top. Write “red” at 12 o’clock, “orange” at 2 o’clock, “yellow” at 4 o’clock, “green” at 6 o’clock, “blue” at 8 o’clock, and “violet” at 10 o’clock. (when finished, red and green should be opposite each other, and so should orange and blue, and yellow and violet.

1. Obtain some of the stock the job is to be printed on, and match the color on that.

2. If you are not sure how to match a certain color, and it is not a PMS color, look for a similar color in the PMS book and see what bases that color was matched with. That will give you a starting point.

3. Start with the base color which is the closest to what you are trying to match, and which will presumably be the largest proportion in the match.

4. Try not to start with a dark color, because if you have to lighten it, it may take a lot of ink to do it, and you might end up with too much ink.

5. Use as few base colors in the match as possible. Don’t use more than 2 or 3 colors if possible.

6. Keep in mind that the farther apart two base colors are on the color wheel, the dirtier the color will be if you mix those two base colors together. The closer together they are on the color wheel, the cleaner the resultant color will be. For instance, if you make an orange out of yellow and magenta, it won’t be as clean as if you make it out of yellow and warm red, or better yet out of orange base.

7. If in doubt about how strong a color needs to be, make it a little on the strong side. It is much easier to weaken it on press than to make it stronger.

8. It is better to match a color a little on the clean side (for instance, if the formula calls for black, don’t put in as much as the formula calls for). It is easy to make the ink dirtier on press but almost impossible to make it cleaner. If the press wasn’t washed extremely well after printing black or a dark color, that in itself will make the color dirtier.

9. If you need to make a color dirtier and darker, you can add a small amount of black. If you need to make it dirtier but not darker, sometimes it is better to add a small amount of its opposite color on the color wheel.

On the subject of using opaque or trans white, keep in mind that all PMS color formulas in the PMS book use trans white only. When using trans white, and depending on how transparent the pigments are in your formula, the light will shine through your ink film to a greater or lesser extent, bounce off the substrate, and come back through the ink film and up to your eye. (This is especially true of the process colors, Cyan, Magenta and Yellow, which are completely transparent). When using a lot of opaque white, the light is blocked from going all the way through the ink film, and just bounces off the ink film.

I know a lot of people on this site use opaque white, and if it works for them, great. I don’t use it, though.

Hope this helps.

Good advice above. One other thing I wanted to point out is that the color swatches in a PMS book are printed with a very thin layer of ink. On letterpress equipment you are probably going to be laying down a thicker layer of ink. That may be the main reason a lot of printers choose to mix by eye and be happy with a close but not necessarily perfect match. The ink is thicker, so less transparent and lets through less light from the paper behind. So, colors generally need more white ink added then what the formula asks for to match the same brightness since it is only the layer of ink itself that you see. When I mix a color, I use the PMS formula as a guide, but I usually must adjust things to come closest to what I want. If I mix a color using the exact formula, I rarely get a print match to the swatch book. I do a draw down on the stock I’m going to be printing on and check against the swatch and then adjust. Another issue, depending on your equipment, is if you add ink to the ink disk by hand when printing you may get uneven inking, heavier when just added and lighter as it runs dry so being exact can be doubly hard to achieve.

PMS formulae are intended for the layer of ink typical with offset printing. Offset limits the amount of ink carried due to maintaining ink/water balance (not fountain solution diluting ink; if you add excess ink, you get scumming and toning in the non-image area).
How do you judge what a given PMS mix may do on paper? I can think of three easy tests. First is the draw-down; dab of ink at the end of an ink knife, squeegeed across the stock to be printed. Next is the tap-out, where you put a small amount on your finger tip and tap it across the stock, which can show variations in density. Another is the roll-out; here you take a small art brayer, load it up with ink, and roll it across a long sheet. As the ink film splits in half with each rotation, there is an obvious showing of darker-to-lighter ink layers.
Letterpress can carry a heavier film of ink to paper, and as PMS base inks are all transparent, the more you lay down, the darker it gets. This is why we add whites, so we can carry enough ink to stay solid, but not look darker. You can go up the PMS swatch with more ink and down swatch with less. BUT, some presses, such as Heidelberg cylinders, and even platens, have such a precise inking system that they can maintain an ink film comparable to offset.
The printers I’ve known who are most successful in meeting the expectations of digital designer customers—who came of age with color-matching software—all use Heidelberg presses, and most run the ink spare. (One even used to lay the ink by offset and then give a blind impression by letterpress: perfect color-matching across card, letterhead, envelopes and other collateral.)
I started before the Pantone system took over, when letterpress and offset inks were completely different, offset inks needing less pigment and more expensive water-resistant vehicle. My first digital designer clients came in the late ’80s, still my C&P days, and with one problem job, I went back to my old press teacher. His response?
“Greens are hard to print. Browns too.”

Thanks Bruce cpd and parallel_imp for your extremely knowledgeable comments. Hopefully those among us who desire to learn more, read our writings which we have taken considerable time to set down for them. I never stop learning too, of course.

I have thought more than once that there should be a place on this site to file articles on a range of basic topics which all printers should know to make their jobs, and the results they achieve easier, more successful, and safer. Safety should be at the top of the list, and the current topic should of course be there too.

Kind regards, Geoff

Thank you all for the suggestions! Some great stuff to try.
I’ve come along faster than I thought I would. Right now I only use the pantone guide to know which inks to use and then eyeball it until I get a good enough looking smear before it goes on the press. From there I’ll correct it as needed and try to keep it close while I’m reinking. It’d be better to have a batch to reink with but my time constraints prevent that on most days. Clients know there will be some variance anyhow.

If you are trying to make a batch to match the ink which is already on the press, you can do a drawdown to compare the press ink to the new batch of ink..

Take a small dab of ink from the press and put it on the left on a pad of copier paper (Don’t use very smooth paper like coated paper). Then take a small dab of the batch of ink you just made and put it just to the right of the first dab. (Don’t use diagonal lines of ink like in the video, just use small round dabs about the size of a small coin).Then take an ink knife or putty knife and pull it down over the two dabs at about a 45 degree angle, pressing down fairly hard as you go. (You may first have to rub some fine sand paper over the blade edge to make it smooth).

The edges of the two inks should join together as you draw them down the paper, making it very easy to compare them. If they don’t join together, put the dabs closer to each other so that they will.

Today I was mixing pms 213 for a job and it made me think back to this thread. The formula guide says 3 parts Rhodamine red and 1 part Warm red but when I mix that I get a very dark version of the color chip, more like 215, on a draw down. I don’t see how anyone, letterpress or offset, following this formula and doing a draw down would be matching 213 but I could be wrong. Maybe my ink is contaminated or something. Can I get some feedback on that part please?
So I put about 6 parts opaque white in a container and then added the other two already mixed reds in small amounts until I got a visual match for the color chip. So, to match this color I had to add about one and a half times as much opaque white by volume than the 2 reds the formula asked for. When I put my mix on the press and printed some samples it was very close. If I tried to use the formula as is it would be too dark.
I haven’t seen any official instructions or formula variations or anything like that that would explain this phenomenon on letterpress but from my experience and on the platen presses that I’m working on that do not have an automatic inking system and using polymer plates, light pms colors have this issue. To make a light color I start with opaque white and then add the colors in the formula.
Does anyone else find this to be true?
Also, from a practical standpoint, I mix ink in a 16 oz. clear plastic soup container that I get from take out. I mix extra so I can have an easy exact match for next time and it comes with a lid so it will stay good for at least a few months with a spray of anti-skin.

Did you do your drawdowns on bond paper, like copier paper? If you used rougher paper than that, the color will appear darker because more ink will stay in the hills and valleys of the rough paper and so look darker.

PMS matches usually come out darker when printed by letterpress because the ink film applied by letterpress is heavier than that applied by offset. Starting from the inked plate, we split the ink film once when we print, with some of the ink going on the paper and some being left on the plate (or type). On an offset press the ink film is split twice, once between the plate and the blanket and again between the blanket and the paper. This makes the ink film thinner on an offset press and is why the ink has to be stronger for offset.

When you mix ink with opaque white, as you said, the ink in the can looks similar to what the print looks like. This is because in both cases the light bounces off the surface of the ink.

Regarding ink mixed with trans white, when you look in the can, you are able to see more deeply below the surface of the ink, so it looks darker in some cases. Also looking at ink mixed with trans white in the can, you can not tell how strong it is. For instance, if you look at PMS magenta base in the can, and then mix 5 parts trans white with 1 part magenta and look at that in the can, they will look the same.

Thank you for that response Geoffrey. I did the same mix and draw down but on smooth paper and I do see that the draw down looks lighter that way, although it still seems a bit darker than the chip in the guide. I guess there’s room for small variations like hand pressure in how much ink gets on the paper.
So, doing a draw down on rougher paper has been working for the press I’m working on since it shows how a thicker coating of ink will look. Not exact but more in the letterpress ballpark.