Blotchy Ink

Hi Guys,

I just mixed my van son rubber based ink with a rubber based mixing white and my ink is splotchy when I print. I mixed the ink thoroughly, but it looks like crap - almost like the ink has leopard spots. What can cause that?

Help please!


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There are many different factors that could cause mottling of the ink. I first take a different paper (preferably machine made paper) one that I know prints well under normal conditions. Pull a couple of impressions with it and see if the stock is the main problem causing it.
If I get like results with an alternate paper, then is the ink on press contaminated with oil or grease grime or paper dust?
If I feel confident that the ink is not contaminated (on press), I look at the ink or inks comprising the mix being used. With a clean knife was the ink skinned in the can and have hickies (dried ink particles) invaded the inking system? Always skin the ink surface of the can as level as possible, avoid gouging down into the balance left in the can, as a clean skinning of it ensures good ink underneath is what ends up on the press. With a clean knife draw some from each can on a white piece of copier paper. Are there dried or burned ink particles in the draw down? If burned ink particles are in the ink, return it to the ink maker as defective as the speed of the ink mill may have burned it.
If the ink simply mottles, no matter what stock it is printed on, you will either have to increase or decrease the tack of the mix to minimize the effect. Hope that helps, good luck!

Have you let the ink mix completely on the disc? What kind of press are you using?

I mix on the disc a fair amount to match colors, and usually I’ll get “leopard ink” as a temporary result, but if the ink isn’t dried out or full of skin, it resolves itself after 4-7 full rotations.

Good luck!

James Beard
Vrooooom Press

I’m using a Kelsey Excelsior 5x8 - and I mix on a glass mixing plate before I add it to the disc.

Calvin - thanks for the guidance it was actually the tack of the mixing white I was using.

Your welcome. Good job! ! !