Ink tack

[janezl]

Is there a way to determine ink tack before usage on press?
In our case, too tacky ink delaminates upper layer of GD duplex board.

What is viscosity/density of ink/fount solution emulsion, that hits paper?
What is temperature of ink emulsion, that comes in contact with paper?

Thanks, Janez

 

[CD102]

Your ink supplier can run a test to determine tack. If you are running out of kits, it should be printed on the label because ink tack is important when determining ink rotations.

 

[Cornishpastythighs]

Just as CD says, ink company should have the equipment (Inkometer) to measure the tack of their ink. Inkometers are very expensive so most printers do not invest in such equipment.

 

[GJOHN]

Ink Tack

Ink Tack

Ink "tack" is the force needed to split an ink film. In the lab. the ink manufacturer uses "Inkometer" to read the tack. But when you emulsify the ink on press, the tack goes down about 50% or so. This was studied by BASF with "graphometronic" instruments that was hooked up to a "live" press during production runs. Not all resins react the smae way when you emulsify it, some visoelastic resins will hold the body and tack better than others. Tack depends on the film thickness on press-the higer the film, the lower the force needed to split it and hence lower tack. Thus a very strong ink, when you have a very low coverage, will impart higher tack than the same ink at heavy covergae. Tack and visosity both are realted to temperature, the higher the temp. the lower the tack and viscosity. Tack is also related to speed of the press, faster the speed higher the tack. That is why web offset inks have lower tack than Sheetfed inks, the quality of papwer is the other reason. When you emulsify and ink on press with aggressive fountain solutions and alcohol substitue, the ink can beak down and will show lower tack and will print fuller dots.
Hope this answers some of your questions.
George John
269-216-8088.

 

[Bob Peterson]

George John,

Would you happen to know if there is a white paper available regarding the testing done at BASF? If there is would you happen to know where I might obtain a copy of it?

Thank you,
Bob Peterson