Stay Open Inks and Dry Time

[Levi M Gibson]

My press guys are constantly pressuring me to use stay open inks. We currently run one shift. Our dry time is ridiculous. Sometimes up to a day or more. Ive noticed other shops cutting the very next morning or the next shift int he bindery. Could the stay open be the issue. We are using an environmental soy based ink.

If its not the inks and the dry time is normal let me know but there are a ton of set off issues along with ink balance. I believe some of the problem to be too much ink and water. just let me know.

 

[Cornishpastythighs]

your press guys have to learn to control the ink/water balance, golden rules of Lithography 'Least amount of ink, Least amount of water' Running a better set of inks might give you a better operating window but will not make up for poor pressmanship.

 

[Levi M Gibson]

Got it thanks for the tip.

 

[Levi M Gibson]

how do can i test that when the sheet is coming off of the press? I am fairly new but have been tasked with Quality Control. I sign off on every press sheet. What are some of the sure fire ways to check if they are applying too much?

 

[Cornishpastythighs]

I guess you can check the solids to see if they are emulsified. A check of your dot gains will also tell you if they are printing mushy ink. If you sign off on a press sheet that is not in balance then the press operator will most likely have excess colour variation during the press run. You must establish what your operating window is with your set of inks,paper,plates and fountain solution and adjust your pre-press files to be able to print the same way every day as long as the press is printing the same way everyday. A word of caution, you cannot establish an optimum print curve if your process is out of control, by this I mean fountain solution mixed correctly and clean, Inking rollers in good condition and set correctly, Plates and blankets packed correctly, Plates processed properly and verified against a standard.
Sounds like you have your work cut out for you Good luck.

 

[Levi M Gibson]

thank you for the input. I really appreciate it.

 

[pdan]

What type of print & paper?
Coated - cmyk?
I've been small press only for 25 years. Stay open inks are about all I use anymore without trouble but only on uncoated stock. All my stay opens have been labeld - For Uncoated Stock Only.

As far as a quick press check - Run your finger over the wet ink. You'll quickly learn how much pressure, not much, but some.
Evaluate how much smear you achieve. About ninety seconds off the press with a coated sheet, I don't want to see the ink smear. Uncoated will not set up as fast, but there should never be much smear immediately pulled from the press in any condition.

Look at some type through a loupe - There should not be tails running, the type should be crisp and clean.

 

[Levi M Gibson]

we run on all different kinds of substrates. I notice that they are running a little heavier than needed on the coated stocks. I will discuss it. Thank you guys for the help! I'm kind of new at this and by new i mean 3 years in but i appreciate all the good feedback.

 

[Lukew]

Stay open inks + fountain solution heavily based on glycols can pose an issue.

We use stay open inks, majority of jobs can be work & turned in under 15 mins, can be printed in the morning & cut end of shift if its really necessary.
We have no rub or scuff issues on matt / silk / uncoated stocks.
We have no carbonising issues when cutting.
No coating used
No IR dryer is used
No Alcohol is used
No glycol based alcohol substitutes are used

We have tested the same inks with this type of fount no drying or bindery related issues. Then tested the inks with glycol based founts immediately the bindery guys are complaining of rub issues, carbonising, scuffing etc.

I can't say for sure but believe we are the only ones using this fount in our country.

We dump the fount and refresh every 8 - 10 weeks, utilising two 50 micron filter bags conductivity has usually only risen by 500 and the water is still relatively clear.
Previous traditional solvent based founts, would require a change every 2 - 3 weeks with a swing of 1000 - 1500 in conductivity and the water would be very dark, near black.

 

[Cold]

Stay open inks contain an anti-oxidant. While in mass this anti-oxidant locks up with the available oxygen and prohibits the ink from oxydizing. At the print film level, the anti-oxidant is so minute compared to the available oxygen that it is quickly depleted from the ink and drying can occur.

When printing heavy 4 color builds and using older generation anti-oxidants, drying issues can occur as the anti-oxidant pools at the top of the ink and is not quickly depleted. For most inks, however, this issue will not occur.

In regards to running too much water, I really like to see the very corner of the sheet scummed, at least at start up. My favorite press operator runs most all of his work in this manner. At this point he can not run less water.

As mentioned earlier, tailing is a decent indicator of running too much ink as well as looking at your dots. There are other variables that can cause an ink to print fat or tail, so keep that in mind.