Ink tack

[Prepper]

What tack would be recommended, or does it matter much, for 20 micron FM screening? We are currently using a medium tack and considering changing to a low tack (for paper picking problems I think). 4 color work on 100# gloss text on a Heidelberg half-size press.

Any input appreciated,
Thanks

 

[gordo]

What tack would be recommended, or does it matter much, for 20 micron FM screening? We are currently using a medium tack and considering changing to a low tack (for paper picking problems I think). 4 color work on 100# gloss text on a Heidelberg half-size press.

It is possible for FM screening to increase the effective tack of the ink which, in turn, can make the tractive force of the printing ink greater than the fiber adhesion in the paper structure, or the bonding of the pigment used in the coating and result in "picking."

best, gordo

 

[Prepper]

So a lower tack ink may actually help with this problem? So not necessarily a bad thing to go lower tack with higher screens, I was just thinking it would increase the gains.

It seemed to be a paper problem and they did replace it.

 

[gordo]

So a lower tack ink may actually help with this problem? So not necessarily a bad thing to go lower tack with higher screens, I was just thinking it would increase the gains.

It seemed to be a paper problem and they did replace it.

Yes, the culprit is usually poor quality paper. If it's a one off problem you can usually fix it by going with lower tack inks or increasing the ink temperature or reducing the speed of the press or using a quick release blanket

If you are going to switch inks permanently then it doesn't matter if the gains are increased because you can compensate with plate curves. But determining if you should change inks permanently requires more research into how your press is transferring ink than just one instance of a picking problem.

best, gordo

 

[rich apollo]

So not necessarily a bad thing to go lower tack with higher screens, I was just thinking it would increase the gains.

Yes, a lower tack ink should increase the dot gain. That's the "glass half-empty" view.

Lower tack inks should more easily transfer from the blanket to the paper, which may be necessary with finer screens. That's the "glass half-full" view.

 

[Alois Senefelder]

Adage

Adage

Gentlemen,

A Lithographic adage: The stiffer the ink, sharper tthe dot

Tack

Successful tack sequence involves three factors: Tack, Absorption and Time

Regards, Alois

 

[RGPW17100]

Reducing tack will create dot gain. If you reduce ink you will have trouble keeping areas over 80% open. I use reducers on solids. As mentioned higher tack is better for printing sharper screens and in my opinion that includes hybrids or FM. If you do have your ink tacked and it is only one color I would not go below a 12. Certain pigments are easier to keep open like Reds however dark Blues like Reflex will probably need to be tacked around 18 to 20 and that may not be enough to hit color and keep screens open. If you are doing 4 color process. Tack 11 yellow, 12 Magenta, 13 Cyan and 14 black would be as low as I would be comfortable with

 

[Alois Senefelder]

Clarification

Clarification

Gentlemen,


1) The choice of ink is for its compatibility with the paper NOT because of the image areas.

2) Image areas include, solids, type, rules and borders besides Halftones !


Regards, Alois

 

[gordo]

1) The choice of ink is for its compatibility with the paper NOT because of the image areas.

2) Image areas include, solids, type, rules and borders besides Halftones !


Regards, Alois

I think you left out "tack" in point one.

I agree with you. Other issues mentioned, like dot gain, can be dealt with using a curve applied during plate imaging. Modifying ink to deal with issues like dot gain is often done in newspaper printing. It is not the right way to solve the problem.

best, gordo