Tack issue

[Artimusg]

We have been running std densities for our process and have not had any trouble until now. Recently when we build a purple it comes out blue. All other process colors are building ok. We have to jack the magenta and stare the cyan to get the color to match. Is this a tack issue/ink issue or has anyone else experienced this.

 

[aqazi81]

We face the same problem when we have heavy coverage of magenta over 100% cyan. Got some success by changing color sequence but not 100% satisfactory results.....

 

[Greg_Firestone]

Just curious what the color build is.

Greg

 

[Artimusg]

The build is a dark purple. Not sure what the pms specified color was. Have had this issue since manufacturers change the ink formula some how. Toyo is the ink.

 

[Greg_Firestone]

Hi Artimusg,

I want to try to rule out prepress being a variable. Just to verify, the job came in with a specified purple spot color. However, this job is being printed CMYK, so the spot color was converted from spot to process. Is this correct? What application created the original file? Also, where and how was the spot color converted. With Adobe's recent release of CS, spot to process conversions are different than they were in the past. I believe they now go through LAB versus using a specified CMYK conversion. This actually gives more accurate results, but the conversion values will vary based on your ICC profile. If your profile is not an accurate profile for your printing condition, you could experience some unexpected variation. I assume this is an offset job... not flexo or digital?

Greg

 

[rapida guy]

Do you have color bars on the sheet? If so, what are the trap readings as measured on the strip? If no strips are on the sheet, I would add them even to other jobs running the same inks and densities.
Seems like a good place to start to me.

 

[Artimusg]

Greg, thank you for your help with this issue. The job did not have a specified purple color that I am aware of. It is what the design team chose. We run these jobs quarterly and we try to match to previous printed pieces as well as proofs that come off the digital. In the past the proofs and previous printed pieces have always looked the same or extremely close. However lately the color shift has changed. Pre press/artist say they are not doing anything different. This is odd, but when we run a process job that does not have any build in color they look fine. It just seems to be with purple or dark builds. We have had 5 so far in the past 2 weeks. Yes this is offset printing, running on a ryobi 524.

 

[Greg_Firestone]

I assume the proofs still look accurate and it's the press which is off?

If it's press related, that's not as much my area of expertise. I would go back to your ink supplier since you mentioned a change from the manufacturer in the ink formula.

Side note: have you updated your proofing color management since the ink change? Any custom ICC color profiles you use would need to be updated.

Greg

 

[Artimusg]

Checked with our pre press and art department and they say the profiles are correct and accurate. Proofs are looking like what we should be getting off press. Ink manufacturer is sending out new ink and was confident this will resolve our issues. Will let you know and thanks for all the feedback. Much appreciated!