Should densities be read before or after varnished is laid down?

[shorty83]

Hi,

I am attempting to build some proof profiles and have charts for press to run so I can read them in for color management. I am wondering if the press guys should be reading their densities before or after they lay the varnish down? The plate fingerprints done for the presses were read in without varnish so I was going to have them run the proof profiles without varnish. Then I got to thinking and wondered what they did for jobs that are varnished...they came back saying they read the densities after they put the varnish down. So which is correct? To read before or after varnish is laid down when running a job?

Thanks in advance,

Molly

 

[gordo]

[SNIP]So which is correct? To read before or after varnish is laid down when running a job?

My understanding (from GATF & Idealiance) is that it doesn't matter.

gordo

 

[Alith7]

As Gordo said...I have this argument...I mean discussion with the pressmen occasionally... we have determined that it really doesn't matter also.

The one thing we HAVE noticed, at least with the Aqueous, is that whichever way it is, make sure that the coating either completely covers, or doesn't touch the color bar. Every once in a while, my pressmen have the coating stop halfway through the color bar, and then they can't get a consistent read.

The only other thing we have noticed is that covering the colorbar with Aqueous, we don't tend to see as much density shifting from dry back. still some, but not as much as without coating it.

 

[RGPW17100]

If you can do either I am assuming that you are running the job waiting for it to dry then putting the varnish on it. This is the only way I can see how you can read densities before the varnish is laid down also I assume you are talking about an oil based varnish and not an aqueous coating. Despite what people say if you run 4 color let it dry and then varnish it later the colors will change. If you are running pantone colors and then varnish later the reflex, purple, violet and rhodimine will burn but not as bad as it does with aqueous. Varnish is seldom used anymore because it yellows with time and takes a lot longer to dry then just running the ink. I would think you would have better control of your color if you run the varnish inline .

 

[rich apollo]

Final product is varnished, right? That would lead me to think that they should be reading a varnished colorbar.

Alith makes a great point, make sure the colorbar is completely varnished or unvarnished - no halvsies.

Have you found that the varnish changes density or color appearance?

 

[meddington]

I would opt for coated measurement assuming coated product, but as a metric of ink laydown, it shouldn't matter. Further on Alith7's point on dry back, note that industry touted densities/CIElab values are dry values, so it could be relevant to know how much shift occurs when measuring wet values.

 

[shorty83]

The varnish is beindg laid in-line. I was just wondering if they should set their densities before turning the varnish station on. Sounds like most press guys set their densities with the varnish down. The densities do change before and after varnish so that's why I was asking, thanks for all the responses!

 

[Alith7]

The varnish is beindg laid in-line. I was just wondering if they should set their densities before turning the varnish station on. Sounds like most press guys set their densities with the varnish down. The densities do change before and after varnish so that's why I was asking, thanks for all the responses!

Umm...if you are varnishing in-line then definitely with varnish down. Otherwise, once you start running, (if the varnish is covering the colorbars) your densities won't match on your check sheets.

....unless your pressmen are setting their densities, and then running the job without checking periodically.....that is a different issue.