Is the paper white Lab a must?

[Dujo]

Hi all!

I have ran into a problem, where my customer wants me to print a testform, that has all values according to ISO12647-2.

The printing part is no problem, I can reach the desired Lab values for the colors, and the dot gain is in the tolerance for all colors, but the problem seems to be the paper white...

In the media standard, I see that the paper white according to ISO must be 95/0/-2 for PT1 and 94/0/-2 for PT2.
My paper is 96/1/-5 so as I see the b value is too much (in negative).
I can't find any tolerances for paper white in the media standard, and I just don't know if paper white is just a recommendation, or a must.
The paper importers, all said, that it is just a recommendation for reaching the right color and dot gain, but the customer is not convinced.

Can anyone help me with this issue? Am I missing something?
I have Heidelberg Color Toolbox, for measuring, and there, the maximum difference for paper white is
Delta L:3
Delta a: 2
Delta b: 2


Where are these values from?? is this the ISO 12647-2 requirement?

[rich apollo]

The values you cite are for paper measured on white backing, and are said to be informative. The normative values are 93, 0, -3 (PT1) and 92, 0, -3 (PT2) for paper measured on black backing. Normative values are necessary for compliance.

[Bloodsaler]

From my test,the paper white not effect the result much,but if your customer insist,you may look for help of your paper supplier.
I`m curious about where you located,the situation in my country is,almost all of the paper not match ISO tolerance~

[Dujo]

Thanks for the replies!
I am located in Hungary, and yeah, the situation is the same here, there are no papers that match the ISO tolerance. (its always the b value) I think it's because they use too much optical whiteners when producing the paper

[Bloodsaler]

Yes,the paper in my country often around 93,0,-5,also the b* value.You may be can think about use the device that got uv cut function~

[gordo]

Thanks for the replies!
I am located in Hungary, and yeah, the situation is the same here, there are no papers that match the ISO tolerance. (its always the b value) I think it's because they use too much optical whiteners when producing the paper

AFAIK there are no papers that match the ISO specification anywhere.

best, gordon p

[chevalier]

LOL how in the world was an ISO specification established for a thing that doesn't exist?

[gordo]

LOL how in the world was an ISO specification established for a thing that doesn't exist?

The answer is obvious - it's the wild and wacky printing industry. ;-)

Actually, I think that the problem came about because of a change, after the specifications were created, in how paper is manufactured. Today calcium carbonate is used as a filler in the basesheet and in the paper coating as a pigment. It provides brightness and a more blue-white shade than clay - the old filler - does.

There's more info here:

Quality In Print: Calcium carbonate - the problem with better quality paper

If I'm not mistaken, using a UV block filter in the spectro is not a solution because there are no standards for UV filters, nor the UV content of the light used by the spectro, nor the light under which you view the sample.

best, gordo

[Dujo]

Have you guys ever heard of "The Paperdam Group" ?
My paper supplier now sent me this
Paperdam Group - Expertise in Paper Performance

Basically they say, that you can achive ISO standard Lab values, and dot gain on any white paper, so it's no big deal if the paper Lab is according to ISO ro not....
But in the ISO standard, paper Lab is a normative, and there is a tolerance
Now I'm even more confused

[gordo]

Have you guys ever heard of "The Paperdam Group" ?
My paper supplier now sent me this
Paperdam Group - Expertise in Paper Performance

Basically they say, that you can achive ISO standard Lab values, and dot gain on any white paper, so it's no big deal if the paper Lab is according to ISO ro not....
But in the ISO standard, paper Lab is a normative, and there is a tolerance
Now I'm even more confused

Oh no. You're not confused enough :-)

In the ISO standard, paper Lab is a normative, and there may be a tolerance - however there is no standard for how the deviation from the standard is measured nor is there a standard for the instrument's illuminant or geometry.

The Paperdam Group points out that, "as stated in ISO 12647-2 and -4 point 4.3, the most important issue is that the proof substrate matches with the production paper. The proof substrate should be specified, including parameters that are common in paper industry."

Unfortunately there are no published standards, specifications or trade customs in the paper industry. *The assignment of a particular grade to a quality category and the establishment of sales policies are made by each individual company. Also, the way that paper manufacturers measure and describe their papers is not the way that printers, or the ISO, do.

The technique described here:
Quality In Print: The issues of Optical Brightening Agents in paper and ink - part 5 of 5

might help.

best, gordo