PMS Inks

[Prepper]

I had a post in the Color Management forum recently titled "dE tolerances of PMS Solids" which we have got worked out now by printing a range of densities and establishing a tolerance based on +\- dE of 3.

Now, my next question is, as it relates to ink color and testing ink batches when new ones come in, is there any recommended tolerances between batches of ink? What do other printers use to judge the inks by? dE or hue\grayness and what would indicate a "bad" batch colorwise, that you would send back and ask them to remake?

Thanks

 

[DotBox]

Here's what we do...

Here's what we do...

...just blame the press crew. Ink is always perfect; just ask your ink sales rep. I've heard it all from those guys. It's NEVER the ink. It's the fountain solution, or a dirty press, or poor ink/water balance, or a lousy pressman, or improper stripes/pressure/density/color sequence/yadda yadda yadda.

If you are a huge facility and your ink consumption dictates that the ink company will bend over backwards to keep your business, then you can pretty much write your own specs for the ink and they'll probably do their best to keep you satisfied. For everyone else, well, ink varies from batch to batch and most of us just have to live with it and make it look as good as we can. If the latter just isn't acceptable in your particular world...gee are you hiring?

 

[chevalier]

DotBox nailed it. If you are big enough you will likely have an in-plant ink lab that will deal with that for you. If you aren't that big the odds are you are going to be at the mercy of the ink company. Many ink companies have cut back drastically since 2008 in both staffing and sourcing of materials which has been very detrimental to quality and consistency.

 

[gordo]

DotBox nailed it. If you are big enough you will likely have an in-plant ink lab that will deal with that for you.

Just a point of interest. I've been told by several ink vendors that they can put an in-plant ink lab into shops that are about $10 million or more in size.

Best gordo

 

[Cornishpastythighs]

Just a point of interest. I've been told by several ink vendors that they can put an in-plant ink lab into shops that are about $10 million or more in size.

Best gordo

Maybe thats because they are using more of those computer controlled ink dispensers nowadays

 

[Cold]

We QC color at a dE of < 1.00 (CIE L.A.B. not CMC) in combination with a human visual approval. This is performed on every batch of ink we make whether it is 1# of PMS 555 or 2000# of PMS 185. I'd be surprised if this isn't typical in my industry for other ink makers.

 

[Bob Peterson]

All of the QC color labs and in-plant operations that I have managed have the following QC procedures once a standard is established:

- All inks must be proofed, following a specific procedure, on a Little Joe proof press.
- The ink must be weighed at .015 ounces and applied to the ink roller. (No using a pipet/volume meter).
- The color must be printed on Leneta Coated Book with NO optical brightener (Leneta.com 3NT-32).
- Colors checked using Lch CMC.
- The reading must be taken with the paper placed over a white ceramic tile.
- Ink containing 50%> transparent white must have a dE of .30 or less.
- Ink containing 25-50% transparent white must have a dE of .50 or less.
- Ink containing <25% transparent white must have a dE of .75 or less.

These are extremely tight tolerances. Although, keep in mind that this is in a ink lab and not on press. Also, the Letna stock w/o optical brightener is used in order to maintain batch to batch color consistency. If a #1 or #2 coated sheet were used, the colors will measure differently every time a different lot of paper is used. The Letna paper is designed to remain color neutral and since it contains no optical brighteners, the only color variation will be the ink. Additionally, the white ceramic tile is used as a backing that will remain consistent, and can be cleaned.

@dotbox - Regarding off shade colors: If the ink salesman knows what he's doing, he should be able to figure out the problem by asking a few questions, and viewing the sheet.

When it comes to solving a problem with process colors, 75% of the time the problem IS related to the press, fountain solution, or using the wrong ink for the application. Don't get me wrong, the ink salesman needs to check the batch of ink your using and see if his other customers are having similar problems. Also, he should never assume that the press is in proper operating condition. Therefore, he should be asking you if the press is set up correctly. What I see more and more these days is poorly maintained presses, fountain solution that is improperly mixed, or it is so contaminated because it hasn't been changed in 2-4 weeks. These maintenance issues are usually due to an owner that doesn't want to spend the money or schedule time for preventative maintenance.

Bob

 

[gordo]

[SNIP]
- The color must be printed on Leneta Coated Book with NO optical brightener (Leneta.com 3NT-32).[SNIP]

[SNIP]Also, the Letna stock w/o optical brightener is used in order to maintain batch to batch color consistency. If a #1 or #2 coated sheet were used, the colors will measure differently every time a different lot of paper is used. The Letna paper is designed to remain color neutral and since it contains no optical brighteners, the only color variation will be the ink. Additionally, the white ceramic tile is used as a backing that will remain consistent, and can be cleaned.[SNIP]

That is a manufacturer's QC process - standardized, consistent, repeatable conditions.

Unfortunately it can lead to the printer failing to meet their customer's color expectations, since the vast majority of papers that printshops run contain optical brightening agents - and they can strongly affect the appearance of the final color.

IMHO it is imperative that the OK'd ink from the vendor be proofed on the paper that the job will be run on - either by the vendor or by the printshop - in order to reduce the chance of color match problems.

best, gordo

 

[Prepper]

Thanks Cold and Bob, more along the lines of what I was looking for. Our use of PMS inks on our covers vs. cmyk was to achieve more color stability on jobs printed over several years, 11 so far now, and we have only used 2 ink suppliers.

I've recently been trying to establish on press tolerances for these inks and ran across the statements that the ink was reformulated a few years ago, from our pressman, when we were discussing variations. Now I have a baseline target, what our established tolerance is on press and was just asking what the tolerance for the ink in the can would be across different shipments and batches.

We now have a target to measure it against and I suppose if we think we have a bad batch for some reason, which we never have as far as I know, but from what you're saying, the ink company can take some from the can we have and test it to see if it meets their targets?

Everyone is human and I've been around long enough to know that almost anything is possible. I do see from what you say that it would have to be tested out of the can to find out, to eliminate the many variables on the press. So is there a report we could get when we order a batch that gives us the color readings for this ink and then in the future if we had the ink company check a different batch, or were working with a different ink company, they could test it against the past readings to check for color or to match what we've used in the past, right?

Thanks

 

[Bob Peterson]

That is a manufacturer's QC process - standardized, consistent, repeatable conditions.

Unfortunately it can lead to the printer failing to meet their customer's color expectations, since the vast majority of papers that printshops run contain optical brightening agents - and they can strongly affect the appearance of the final color.

IMHO it is imperative that the OK'd ink from the vendor be proofed on the paper that the job will be run on - either by the vendor or by the printshop - in order to reduce the chance of color match problems.

best, gordo

@gordo

You are correct, proofing it on the printers actual run stock would be the best. However, when I worked in in-plants, we would have to do this. 50% of the time, primarily in light colors, the color had to re-matched, to a previously printed job, due to the optical brightener content differing from one lot of stock to the next.

Unfortunately, in this market we are now in, ink companies are not given the actual run stock when an order for a Pantone color is ordered. Also, with the various aqueous coating utilized i.e (satin, matte, dull), these too will affect the final color. There is no way for an ink company to supply a standard ink to match. Therefore, when a printer tells the ink company that the color doesn't match, it is usually due to the printer ordering a color and expecting it to match no matter the application.

The sad part of this entire situation, when an ink company tries to educate their customer regarding these situations, most time they don't want to hear it, or they just blow it off as we have no clue what we are talking about.

Bob

 

[Bob Peterson]

Thanks Cold and Bob, more along the lines of what I was looking for. Our use of PMS inks on our covers vs. cmyk was to achieve more color stability on jobs printed over several years, 11 so far now, and we have only used 2 ink suppliers.

I've recently been trying to establish on press tolerances for these inks and ran across the statements that the ink was reformulated a few years ago, from our pressman, when we were discussing variations. Now I have a baseline target, what our established tolerance is on press and was just asking what the tolerance for the ink in the can would be across different shipments and batches.

We now have a target to measure it against and I suppose if we think we have a bad batch for some reason, which we never have as far as I know, but from what you're saying, the ink company can take some from the can we have and test it to see if it meets their targets?

Everyone is human and I've been around long enough to know that almost anything is possible. I do see from what you say that it would have to be tested out of the can to find out, to eliminate the many variables on the press. So is there a report we could get when we order a batch that gives us the color readings for this ink and then in the future if we had the ink company check a different batch, or were working with a different ink company, they could test it against the past readings to check for color or to match what we've used in the past, right?

Thanks

@Prepper- Tell your ink supplier to provide you with a Certificate of Quality for each and every batch you receive. Have them include the L*a*b* values. You could also have them provide you with a proof/draw down from each production batch, on a stock of your choosing.

 

[Prepper]

@gordo and bob,

I agree with you both, to make sure that just the ink is the same it would have to be tested out of the can and checked against previous readings at the ink company.

As far as the printed color on paper, I also now have target readings, albeit on one single stock, to shoot for and compare to. If it turns out different on another stock next month, I could check the 2 stocks against each other to look for differences there. We change stock like most people change pants and sometimes like a baby changes diapers nearly, 3-4 times a day! But it is all 100# gloss text and all our PMS cover colors are darker shades, so that tends to help with paper variation I would think.

Terry

 

[gordo]

RE:

@gordo and bob,

I agree with you both, to make sure that just the ink is the same it would have to be tested out of the can and checked against previous readings at the ink company.

@Prepper- Tell your ink supplier to provide you with a Certificate of Quality for each and every batch you receive. Have them include the L*a*b* values.

Just to throw a wrench in the monkey works... instruments, even the same model from the same manufacturer rarely agree - particularly if you are hoping to get a delatE no greater than 1.

Some of the reasons for the difference in reported values are explained here: The Print Guide: Top reasons why color instruments don't agree

So, it's best to take a holistic approach, try to have clear communications between your production staff, your ink vendor, and your print customer, then hold your nose, close your eyes and pray for it to all work out. Sometimes it does.

best, gordo