Solid Ink LABs - GRACoL 2006 & GRACoL 2013

[Vernon Roberts]

Hello,

I'm currently evaluating our solid ink LABs. I have received a certificate of analysis and compliance from our ink manufacturer that states it's in compliance with ISO-2846-1 as directed in ISO 12647-2.

Right now, when referencing GRACoL 2006 and averaging 10 it8s, measured with an X-Rite iSis in M0 mode, yellow and paper white are out of spec. My pressroom manager says they can't run density any higher. My theory is the paper white is affecting yellow. I can convert my paper white to the standard in Color Toolbox (what I'm working in), that does what I guess is a simulation of CMYK and RGB solids. All deltas improve when I do this. My theory is optical brighteners in the paper are making the paper bluer, and thus affecting yellow the most, because of it's transparency.

I'm looking to upgrade into a complete M1 workflow, but right now everything is too new and I don't have RIP support yet. I'm asking for opinions on what else could be the problem or if it is the paper whiteness, what can I do? Adjust my standard and live with it? What about proofs? Thanks

 

[gordo]

What are your SIDS?

 

[Vernon Roberts]

What are your SIDS?

1.80 K
1.35 C
1.45 M
1.05 Y

These are the wet densities, but I averaged the it8s dry.

 

[gordo]

1.80 K
1.35 C
1.45 M
1.05 Y

These are the wet densities, but I averaged the it8s dry.

Assuming a Status T non-polarized M0 instrument, for wet densities (which may be more dry than you think), except for K, you're low (expecting a 0.05 drop in density reading going from wet to dry.) Your SID readings may also be the result of instrument to instrument variation.

Here are the olde shoppe standard ink densities dry measurements:

K 1.70
C 1.40
M 1.50
Y 1.05

Below, on the right, is a chart of SID maximums (based on my experience at many shops)

Yellow SID tops out at about 1.20-1.25 - so he should be able to go higher - maybe 1.10-1.15 without the ink film thickness causing issues if that'll help you align.

What you watch for as SIDs increase are ink "tailing" (a.k.a. misting, slinging) ( The Print Guide: Every letter tells a story - print problems revealed in type reproduction. ) and set-off in the delivery stack - you want to be below that point.

 

[rich apollo]

Your paper will conform to GRACoL_2013 spec.

You can adapt your target colors to the white point of the paper; there is an Excel spreadsheet on the IDEAlliance web site to do this.

You could use a test form like the attached to find if there is a yellow density that will get you in spec. It'll vary the ink take-off across the sheet so you can find the sweet spot. (credit to Darrian Young for this idea - at least he's the one that I heard it from)

For proofing, you could a) create a custom press profile, b) edit the white point of the GRACoL_2006 data and build a new profile, c) perform a white point edit on a GRACoL_2006 profile.

 

[Vernon Roberts]

Apollo,

I have that spreadsheet, it only has the new datasets, not GRACoL 2006. Will my color be worst or better if I use GRACoL 2013 spec with out calibration with an M1 device?

Gordo, the densities are read with a spectro scanner straight from a pull, so they are wet. I've checked before, but I'll have to check again, they are using Status T, no filter.

 

[Vernon Roberts]

I guess the point of an M1 device doing calibration is to better measure the difference in optical brighter amounts from proof paper to press paper, helping to create proofs that are easier to match.

 

[gordo]

Gordo, the densities are read with a spectro scanner straight from a pull, so they are wet. I've checked before, but I'll have to check again, they are using Status T, no filter.

I guess I'm thinking that if the data sets are from 2006 they'd be from dry sheets. Even 2013 data judging from how the papers are handled they'd be dry. So measuring wet would introduce a difference. Best to know the shop's dry back to accommodate as required.

 

[rich apollo]

Apollo,

I have that spreadsheet, it only has the new datasets, not GRACoL 2006. Will my color be worst or better if I use GRACoL 2013 spec with out calibration with an M1 device?

1) I don't know.

2) I have the spreadsheet with GRACoL_2006 (TR006) data. PM me if you'd like a copy of what I have.

3) You should be able to edit the reference data. You can copy in the data set that you need to work with.

 

[Vernon Roberts]

1) I don't know.

2) I have the spreadsheet with GRACoL_2006 (TR006) data. PM me if you'd like a copy of what I have.

3) You should be able to edit the reference data. You can copy in the data set that you need to work with.

You're right, if I could managed to not fudge it up. I would like to take a look at the spreadsheet you have. I appreciate that very much.



Gordo, The densities I posted are only aims for the press operator. I'm not really concerned about the dry density, only the dry spectral data. My pressroom manager is on vacation at the moment, I'll see if they think it's anyway possible to push yellow more. Switching over to GRACoL 2013 as our process standard does help paper whiteness and yellow. There's a reason to keep updating data sets.

 

[gordo]

You're right, if I could managed to not fudge it up. I would like to take a look at the spreadsheet you have. I appreciate that very much.



Gordo, The densities I posted are only aims for the press operator. I'm not really concerned about the dry density, only the dry spectral data. My pressroom manager is on vacation at the moment, I'll see if they think it's anyway possible to push yellow more. Switching over to GRACoL 2013 as our process standard does help paper whiteness and yellow. There's a reason to keep updating data sets.

OK but realize that, from a press operator's point of view an offset press does NOT print color. It lays down an emulsion of ink and water. That dynamic is what the press operator is concerned about - consciously or not. If he/she exceeds the tolerances then the press will either be unstable or the lithographic process will fail. So you cannot/should not only be concerned with spectral values and not densities.

 

[Deleted member 16349]

OK but realize that, from a press operator's point of view an offset press does NOT print color. It lays down an emulsion of ink and water. That dynamic is what the press operator is concerned about - consciously or not. If he/she exceeds the tolerances then the press will either be unstable or the lithographic process will fail. So you cannot/should not only be concerned with spectral values and not densities.

Lots of wrong thinking going on in this industry is how I see it. Printing devices are not colour devices.

Printing devices place pigments on substrates. This results in colour. Colour is a byproduct of the process.

Aiming at colour targets for process inks is in fashion now but it is not the right thing to do IMO. Inks do not have a specific colour. Instead of accepting the colour of how a process ink prints and managing the colour from that point, the industry seems to want to force the idea that the printed ink should have a specific colour, which it does not tend to have. So the result is that one starts out with an error right from the start because the target colour can not be obtained.

Accepting this initial error seems to be perfectly OK with the experts who then develop methods to move the spectral values along the curve that goes close but does not get to the target spectral colour. Of course these kinds of methods are not so easy for an operator to use.

Process control. You can get to a density target but you can't often get to a colour target. If it is not possible for you to get to a target, you don't have process control.

 

[rich apollo]

You're right, if I could managed to not fudge it up. I would like to take a look at the spreadsheet you have. I appreciate that very much.

Here's what I have.