One of the most often asked questions in lithography is how do I know when to modify my ink? The question right behind it is, how do I modify my ink?
How do I know when to modify my inks?
Lithographic inks should be designed so that they do not require modification to print. They should print right out of the can about 80-90% of the time. The other 10% of the time you should only change that property of the ink that is not performing to your expectations.
There are 4 basic properties of ink:
- Length - Can be measured by putting an ink knife in the ink and then drawing the knife straight up. The thread of ink that is generated will indicate the length. Long or short.
- Tack - This is how sticky the ink is. Usually long inks are very tacky
- Body - This is the stiffness of the ink. Does it stand up like putty or run like honey?
- Grease content - This is the amount of grease, natural or otherwise, in the ink.
There are 3 basic Ink modifiers
- Magnesium carbonate - A white powder that stiffens, reduces greasiness, and reduces tack and length. It also has the property of holding the ink together.
- Varnishes - 00 Reduces tack and length, increases greasiness, reduces body
#3 Reduces tack and length, increases greasiness, reduces body
#5 Increases tack and length, reduces body
#7 Increases tack and length
- Reducers - Reduces length and tack
Properties of ink are interrelated. You cannot change one property without to some extent affecting another. Stiffening ink with a stiff varnish also increases tack. Let moderation be your guide. The more you modify an ink the less likely it will be to print without problems.