Printed Uncoated PMS on Coated Stock

Question

I did my artwork on the uncoated PMS colours as I originally planned to print it on uncoated stock. We ended up changing the stock and there was the forgetfulness of one person to not change the PMS colours.

The colours (well mostly the gray) are very light. So my question is, if I change to the coated colours, will the colours be even lighter or will they be darker?

The reason I ask is because it's packaging, and I am using two different companies and the other uncoated stock needs a big adjustment as it's printed on quite dark white paper and since I am using gray it makes a lot of difference.

I also didn't want the gray to be so light as it should be closer to the Pantone book.

Answer 1

A Pantone specification is a Pantone Specification. Pantone ink formulas do not change based upon coated (C) or uncoated (U) stock.

The Pantone specification books all print the same ink colors. The difference is how that ink looks on different stock -- C or U -- not the actual color of the ink. Uncoated stock absorbs more ink. So there is a natural pigment change when printing on uncoated stock. Coated stocks absorb less ink so colors tend to stay more opaque (or solid).

The digital color books appear as different colors for the same reason -- they are different so that on screen there's a better visual representation of how that ink appears when printed, but it is still the same ink formula. And that same formula is used on press. To the pressman, there's no difference in the ink he/she grabs between Pantone C and a Pantone U -- it's just Pantone Warm Grey 5.

So, in short, there's no reason to switch from something like Pantone Warm Grey 5 U to a Pantone Warm Grey 5 C. It's the same ink. The only possible caveat is to switch to a C color so that your digital file better visually represents the final printed piece, but there's no technical reason you need to switch from a U color to a C color.

Look at a Pantone color guide and check your colors to see how they will look on coated stock.

If then, you are unhappy about how the color appears you may need to change the actual Pantone value to a different color entirely. I.E. if you are unhappy with how dark Pantone Warm Grey 5 appears on coated stock, you may want to change to Pantone Warm Grey 4.

Ultimately, for color critical work, you should get (or ask for) a color proof or Chromakey for the job so you can verify colors before anything is actually run. Note: Not a PDF proof.. an actual hard copy color proof. Most decent press houses can FedEx overnight a proof to you and you can FedEx it back.

Answer 2

Needs a big adjustment as its printed on quite dark white paper

Color is a totally relative thing. It depends on the light, the surrounding colors, the color of the paper. This first part does not depend on if the paper is coated or not, so you need to make a choice on what is your target color.

Now, yes, we need to see how the ink reacts to a specific kind of paper.

• Transparency of the ink, some halftone screen, consistency. (Offset print ink is diferent than silk printing one)

• How this ink is absorved by the paper (Coated, uncoated, roughness)

So you can take diferent aproaches.

1) A teorical one, where you re-define a diferent pantone for diferent paper, where you are probably limited to the information the color formula guide gives you.

For example the Cool Gray 1 U Patch looks like the Cool Gray 2C.

But for grays are easier than other colors.

2) Profile adjustments. In the case you are not printing spot colors, but CMKY you can use a diferent profile and the cmyk values will change when converting the spot color.

3) A "visual aproach one". You tell the printer that the color should look like a Cool Gray U, and if the print run is small, they can adjust a bit the preparation of the ink, or inclusive the ammount of ink on the press.

4) But in this particular case you have a "dark paper" which is not a standardized white. In this case I would "simulate" a sample.

a) Use the same type of paper you will be using, and prepare some patches on an ink jet paper.

b) Prepare a sample with this paper and the color you like, and send it as a physical guide.

Now they provider can help you decide modifying some other factors you can not, like the transparency of the ink or, again the amount of it the press delivers.

This final ink probably is not the real formula of the cool gray, but an adapred one acording to your sample.

This works if the print house can prepare small amounts of ink themselves. Some big ones only accept spot colors prepared by kilos by the ink provider, based on a formula.

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Edited to be more specific:

If you have an U color, it will be lighter on a coated paper.

If you have a C color, it will be darker on an uncoated paper.

Answer 3

The can of ink is exactly the same for coated or uncoated Pantones. It doesn't matter if you use C or U; it only matters if you ever decide to convert these Pantones to CMYK.

The paper will make the ink react in a different way because of the dot gain; how the paper will absorb the ink. The C or U is just a screen preview to help you during your design process, but the can of ink at the print shop is the same for both.

About dot gain:

https://www.youtube.com/watch?v=O8hG0VIViNo

Regardless of whether a color is C or U, the ink is made the same.

http://info.universalprinting.com/blog/bid/51807/Choosing-Inks-for-Color-Printing-Coated-vs-Uncoated

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Note that some printers can modify the ink for you and create a "custom" ink. But if you decide to go that road, you better not change printers too often! They will note down your special gray recipe and use it if you need to get other stuff printed.

Also, a note about printing: if you use a pure Pantone, each press can be manually adjusted as well, so even from one print run to another, there can always be small variations depending on how much the printer cares about consistency, and this can also be slightly different from one printer to another. But it can also help you to adjust your color slightly if you can be present when they start printing your batch of boxes.

Sometimes printers don't even use "real Pantone" inks, they create their own matching recipe. That's understandable and that doesn't mean the colors won't match but that's one part of the reality about "Pantones being always a perfect match". Printing is like cooking, you need fresh inks and fresh paper. For the same reason, not all printers keep in stock all the different kind of inks that have different base. You can search online for ink sellers, you might have hard time finding a "coated" and "uncoated" formula but you might find additives added to the inks to change their viscosity though, inks for different purpose (eg. laser resistant, dries faster) and there's different base for inks as well (eg. soy, oil), as there is for paints.

Will a Pantone Reflex blue look darker on an uncoated paper than a coated one?

Yes and no. Depending on the quality of the printer, a Pantone may look more "saturated" because the ink absorption wasn't properly adjusted to the paper or because your own images were not calibrated for uncoated. If the images are saturated then it could be what you call "darker".

The color might look brighter and "luminous" on most coated stock but that has also a lot to do with the brightness of your paper too. On a very ultra white and bright stock that is uncoated, that Pantone could look better than the same Pantone printed on a low quality coated paper that isn't ultra bright. Same goes for a laminated or a print that has a varnish applied; it might darken a little bit the final result. Since the inks used for offset are not fully opaque, not only the ink absorption will affect the final result but the color of the paper itself will also influence this.

If you are really unsure, the best thing to do is to go at a high quality print shop and ask for samples to compare the results. And ask questions. They know their stocks and inks. You can even ask for a test if you have the budget for it or if they already have the ink in stock. A printed proof will not give you a good rendering of the final result because there's no proofing system that use true Pantone inks. But the print shop can do a test on the stock you chose and that can give you an idea of the final result. If you're using Pantones colors that aren't very popular, it might be hard for you to know exactly how the final result will look like and that's one of the challenge of working with different stocks and inks. You might not get the exact result you have on your screen but the goal is to get as close as possible to it by combining quality of print, stock, brightness, varnishes, etc.

Photoshop has settings to adjust your dot gain or you can do it manually by changing your 100% densities to 85% when you know you're preparing a file for uncoated stock. But before you do this, you might want to discuss with your printer, sometimes they do adjust it as well.

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Very good reading from the Mohawk fine papers company:

http://www.mohawkconnects.com/sites/default/files/content/pdf-education/14.%20Naked%20Truth%20pt%201.pdf

How to use the Pantone system

http://www.colorguides.net/how_to_use_pantone.html