Gracol 2006 and 2007 Specs

[Bill W]

Greetings,

I noticed that there is a small difference between the Lab values in the 2006 and 2007 specs. The largest dE difference is between the blacks (2.22 dE based on CIE2000).

Please correct my thinking if I am off base. It seems to me that the color of black is very important because gray balance is achieved by replacing black with the appropriate values of CMY. If the black has changed will that not change the needed values of CMY. Which in the case of flexo means different TVI curves.

I have already spent numerous hours on presses in two locations getting three ink companies to bend their flexo inks to be, on press, under 2 dE's to the 2006 spec. I cannot in good conscience live with a 5 dE difference. Especially if the difference is based on inks traveling from the positive to the negative side of the a or b axes.

I will be visiting both of these plants in the next few weeks to test my curves. It is now a good time to have the ink companies change the inks a little to match the new spec? And, if I do that, since the two specs are not that far from each in color, should I trust any changes in TVI that IDEALink reports with the change in inks to not test it before I do my final profile run.

Thanks to all that answer.

-Bill-

 

[meddington]

Re: Gracol 2006 and 2007 Specs

>I noticed that there is a small difference between the Lab values in the 2006 and 2007 specs. The largest dE difference is between the blacks (2.22 dE based on CIE2000).

Could you be specific in where your getting the lab values? Prior to Gracol 2007, no Lab values were published in the specification, so I'm confused what your actually comparing.

>It seems to me that the color of black is very important because gray balance is achieved by replacing black with the appropriate values of CMY. If the black has changed will that not change the needed values of CMY. Which in the case of flexo means different TVI curves.

Graybalance for CMY is calibrated independent from the black, and therefore, from a calibration perspective, there would be no change in CMY curves needed. If the black ink changes (either in the spec or from an ink change on press), but the CMY hasn't, this should not affect the CMY values needed to achieve gray balance independently at all.

From a profile/color separation standpoint, however, black is replacing the graying compenent in the CMY build, and a change in hue here could affect gray balance on press, even while hitting CMY grabalcance aims...depending on how big a change in black we're reall talking about. The place to make a correction for this would be in the ICC profile you create. Meaning that if just the black ink changes, you'd want to ensure you still hitting the NPD curve for black as defined in G7, but also that you ICC profile is updated. Basically, if you build a profile, and then the black ink is changed, it could affect the results on press. But I wouldn't expect a profound difference with 2.2 dE2000.

The question to ask yourself (as it was before) is how close is the black performing to the published Lab values and NPD curves. If your within tolerance, you should be ok.

>I have already spent numerous hours on presses in two locations getting three ink companies to bend their flexo inks to be, on press, under 2 dE's to the 2006 spec. I cannot in good conscience live with a 5 dE difference. Especially if the difference is based on inks traveling from the positive to the negative side of the a or b axes.

You mentioned that the difference was 2.22 dE2000, and later that you couldn't live with a 5dE(76) tolerance, which mixes two diffrent forumlae. So, did the ink companies bend the flexo inks to within 2 dE 76 or 2000?

 

[Bill W]

Re: Gracol 2006 and 2007 Specs

Greetings Michael,

Thank you for the clarifying questions regarding the numbers I quoted. It seems I need to do some checking myself with the numbers I received regarding ISO 12647-2. I need to do some checking and will address this later.

I am using an Xrite spector-denistometer and I have set the delta E tolerance to CMC and Lab method to CIE however I see not way to select 2000, 76, or ? I have been using PatchTool to compare my press runs to the "standard" I had received as 12467-2 and it uses CIE DE 2000.

One of my challenges is maybe trying to get G7 going for flexo while the flexo community stills debate it. As usually my questions seem to only lead me to more questions.

More to follow in the next few days.

Thanks again for your interest and feedback. Oh yeah, I am having my ink companies, I have to work with 3 different one, bend my inks to match what I thought was a correct set of numbers but now I am not sure. I do believe that what I have done is not in vain and I can still make this work.

-Bill-