Offset Print Job on Uncoated Paper fades within weeks for no known reason

[Tim-Ellis]

Hello folks,


I really need your help. Our sister company has trouble with an offset job. The Cool Grey 5U looks OK when it's printed but after just a few weeks it fades.


Attached is a photo of the target, the first print run and the second print run. You'll see the first run is a little out but second is way off. I've had to blur out the clients details. The second photo has the LAB readings and some other info.


The job was stored in the usual way and not exposed to intense light. It's the same paper and the same ink supplier. They are now thinking it's humidity.


I don't have all the info to hand as they are in North West India. They print to ISO Standards 12647-2 and use PressSign to verify their work. They are a pretty good team with a good track record.


We are all out of ideas. Does anyone out there have a clue?

 

[Cornishpastythighs]

Does the humidity change that much in their factory that it could cause this issue. Do they monitor humidity in the plant on a daily basis? The equipment that can monitor Humidity is not very expensive. Have their ink supplier perform a Light fastness test on the inks. Are you certain this is ink fade and not ink dryback?

 

[curiosity]

clarification please.
OP said: "The Cool Grey 5U looks OK when it's printed but after just a few weeks it fades."
But then you show us a 1st and 2nd run. Do you have an example of a run after a few weeks, faded?
The 2nd run looks like a huge problem. Or is the 2nd run, the faded example?
As for humidity, this article: https://www.q-lab.com/documents/public/c1e61671-f8b7-4ba1-a4ea-1d91cd306592.pdf
suggests that humidity did not make a difference with the inks they tested.

 

[Tim-Ellis]

Does the humidity change that much in their factory that it could cause this issue. Do they monitor humidity in the plant on a daily basis? The equipment that can monitor Humidity is not very expensive. Have their ink supplier perform a Light fastness test on the inks. Are you certain this is ink fade and not ink dryback?

Hiya - I am fairly sure the production area will be temperature controlled (I am checking). They are wondering if the paper had been exposed to different humidity conditions before it arrived to them. I will ask about the Humidity monitor. The inks suppliers says that they have performed light fastness test on the ink. Ink dry back does seems the more likely to me. I'll try to get more details today.

 

[Tim-Ellis]

clarification please.
OP said: "The Cool Grey 5U looks OK when it's printed but after just a few weeks it fades."
But then you show us a 1st and 2nd run. Do you have an example of a run after a few weeks, faded?
The 2nd run looks like a huge problem. Or is the 2nd run, the faded example?
As for humidity, this article: https://www.q-lab.com/documents/publ...91cd306592.pdf
suggests that humidity did not make a difference with the inks they tested.

Hello - So sorry for any confusion.

I will ask them for the PressSign reports so you can see the dates of the runs. At the time of printing, both 1st and 2nd run looked like a good match for Cool Grey 5U. They should have both had a delta E of less than 1.5 when the job was in finishing. Today Run 1 looks ok (ish) and Run 2 looks closer to Pantone 7535 U than it does to Cool Grey 5 U.

I'll get you more information when I have it .... Thanks for the article!

 

[Alois Senefelder]

Hello Tim-Ellis,


Chemical Fading - Check the following 1) pH of the paper , Coated/Uncoated 2) pH of the Fountain Solution 3) Moisture Content of the Substrates

Irrelevant ---- Quoting L.a.B. values !!!!


Regards, Alois

 

[Tim-Ellis]

Hello Tim-Ellis,


Chemical Fading - Check the following 1) pH of the paper , Coated/Uncoated 2) pH of the Fountain Solution 3) Moisture Content of the Substrates

Irrelevant ---- Quoting L.a.B. values !!!!


Regards, Alois

Hello Alois,

Thank you so much - I'll pass that back to the team.

"Quoting L.a.B. values !!!!" - sorry - just wanted to communicate exactly how far the colour had moved and in which direction.

Thank you again.

 

[D Ink Man]

Most likely, your ink supplier is tipping that spot color with something other than the dastardly pAntone formula to give an acceptable match on the particular paper stock you are using. If truly it is the pigments of the pMS book formula, black and 072 blue, you should know these 'exact' pigments are lightfast even in the relatively low percentages contained in a color like CG#5. If the ink supplier is incorporating any other pigment to accommodate a good match, this COULD BE your problem. For instance, if the ink supplier used Alkali Blue G.S. as the blue portion, the problem is solve. Tell them to use Victoria Blue or find another supplier. It the inky also tipped the match with a fugitive pigment (could be any number of types), this could be your problem.

Secondly, it could be the substrate. Give adequate sample of your job stock, along with "2" other random samples of a similar offset paper, with the same grade, basis wt., (make sure to indicate cover or text) at approximately the same brightness and whiteness level as your job stock also. You may have to ask for paper samples from paper vendor, but I would recommend not to get him involved in the analysis and evaluation. Ok, once you have all 3 stocks, submit them to your ink guy and have him proof the CG#5 to proper shade density. Then have the inky, proof the same "VOLUME" or "WEIGHT" of ink on the other 2 alternate stocks. Don't worry about shade variation on the other 2 stocks. Just that the same IFT is laid down. Have your inky measure L*a*b values on his spectrophotometer freshly printed and then 24 hours later after drying has occurred. Tell him to keep going; he needs to run all lab proofed in a fade-o-meter (usually an Atlas brand), for 24-48-72 hours. Then after 72 hours read L*a*b values on each patch of the time intervals. So that would make for a total of 15 separate values. Not finished> Also do the same to each virgin paper stock. As is, 24-48-72 for a total 12 readings for paper only. So at the end of the evaluation you will have 27 total L*a*b values for the subjects aforementioned.

And..... I promise you with 99.98% certainty you will have the answer to your problem.

If your ink man, ink company cannot or will not do this for you I have one suggestion. FIRE THEM and get, well you know..........

D Ink Man

 

[Tim-Ellis]

....

And..... I promise you with 99.98% certainty you will have the answer to your problem.

D Ink Man

Thank you D Ink Man,

I have passed that on to the boys at the Sister company. I am fairly sure that by now they will be shopping around for a new supplier.

 

[D Ink Man]

Back to the CG#5 printing problem. The methodology recommended will certainly 'find out why'. So you potentially have the means to do what I aforementioned in the previous paragraph. So, it is felt that now with this in possession, the answer will be revealed by the ink supplier, without the testing I descriptively laid out. That seems like a lot of work you may say. It really is not, for an ink company that wants to keep your business. Give them a chance to be honest with you. You cannot print xxx,000 number of impressions and have failure like this. Work it out it with them, reach accord and then carry on. They may rise to the occasion if they are worth their salt..
D

 

[D Ink Man]

Even when we try to control our variables, we often assume that the variable we're controlling is a consistent one. I've found over the years that the consumables (variable) we use in the industry, aren't always made consistently.

Sometimes a way to find out is as simple as trying another batch of something, or a different brand.

Just SWAG at it huh, ali? D

 

[turbotom1052]

One of the problems that I've encountered when printing ANY color, that has a very high transparent white component, is that just about any variable in the process, can result in problems with color matching. For example.... the slightest traces of a previous color, still on the rollers from another job, has the ability to greatly influence the color your printing. In this scenario some guys will wind up chasing their tails, adjusting for a color match, only to have the color change during the run. Its for this very reason I like to tap out the ink thats on my rollers, and compare it to a tap out of the ink from the fountain. This tap out is best done on a gloss coated sheet. Your best chance of consistent color from beginning to end of a press run will happen, when the ink on your rollers dead matches the ink in the fountain.
The other variable that will have great influence on any light colored ink will be any variations in the stocks shade. If you start a job running a bright white sheet and the next batch of paper winds up being yellowish then your color will be greatly affected. Same thing with variations in a sheets holdout. This also holds true when it comes to a stocks felt side vs. its wire side!!!
It should also be noted that both hand held,and closed loop scanning densitometers are notoriously inaccurate when delivering sub .25 readings. When a light color can only muster a reading of 25 it takes a pretty large amount of additional or less ink to register a reading of a couple of points up or down. This variation of a couple or 3 densitometer points can greatly affect the color you see.
Its for this reason, that at times its best to, at the very least use your eyes to VERIFY what your densitometer is telling you. Im not at all opposed to not even bothering with the densitometer when printing such colors. Ill even bypass that color when it comes to closed loop inking corrections, and substitute my eyes and pressman skills. Ive seen more and more, a total and complete dependance on technology, cause the very problems the OP has written about.
Its no surprise to me that these things happen more and more, as the level of craftsmanship that was once the driving force in a pressroom, has been replaced with managements mentality, that modern technowizardry is all thats needed to be successful in a pressroom.

 

[D Ink Man]

Formulation #2 of the Day: (For Variable #1 from turbotom1052)

Drag-Out Varnish:

Now this product should be employed before running any light tint (95% Trans White or more), pasters, invisible fluorescents, day glo type flurorscents and/or critical colors where you need exact reproduction of the color in the can on the paper.

Your ink supplier (ha-ha), should be able to provide you with this. It is a free flowing, low viscosity, but very tacky clear drierless varnish that should be run, idled through the press unit for 1-2 minutes. Think of it as a shampoo. Lather, rinse, repeat. Spray down your trains withappropriate roller wash in between shampoos and you can approach a clean and sterile unit. You will know if you have the correct product, if you are easily able to dig it out of the container, but find it very difficult to control the cotton candy type of filament strings that follow the gloub on your spatula.

For novice ink makers, just take some modoified hydrocarbon resin and melt it into just enough of diluent to solubilize it to clarity. The diluent you should use is.........well what the hell inkies, you want me to deliver it to the printer too?

D

 

[Tim-Ellis]

Thank you everyone so much for your great advice. I have passed it all on. As yet, they have not found the cause but they tell me they are working closely with the Ink Supplier to get to the bottom of it. They are certain that is where the problem is. The problem seems limited to these few press runs only. My money is on the pH of the Fountain Solution but I'll let you know if we get a definitive answer.