Patchy print - seems like a stock problem?

[dagoof]

Was wondering if anyone could advise - we had postcards manufactured by a 3rd party, which we later overprint. For our latest batch we went with a new coated stock, however, it's causing major problems with overprinting, specifically weak patchy print (not to mention the fact it doesn't seem to dry on properly, it's still off-setting after almost a week!).

We can run waste through on 3 different previous coated stocks, all perfect, then as soon as it hits the new stock it's patchy. We've mentioned our concerns to the manufacturer but they suggested it was our press, I'm not convinced given the above.

Is it possible they could have been sealed in some way that prevents overprint? Any other suggestions?

[Freeman A.Gain]

They possibly coated it?

[dagoof]

It's wasn't UV'd or Aqueoused - is there any other sort of seal that could have been applied?

[Kaoticor]

Have you checked the thickness on the new stock? That wouldn't affect the drying, but is something simple you could check for the "patches".

[Freeman A.Gain]

Was it done digital? May be a fuiser oil?

[dagoof]

Kaoticar - the thickness is pretty much the same as previous stock and the press is set for maximum impression.
It's definitely litho work Freeman.

[saso777]

Can you ask them what ink they use and if they put something in ink while printing

[RGPW17100]

Uncoated side of boards are always problematic. I was told they were to alkaline and cause the ink driers to fail. We use carolina and it prints fine. Lower quality boards like Kolima we have to use more driers in the ink and have noticed splotchy ink lays. You get what you pay for on board stock. Everybody keeps making it cheaper and that makes it harder to print on.

[dagoof]

Saso - do you mean an additive at our end or the manufacturers?

RPG - it's coated both sides.

[Ajax]

Are you finding a megaton of spray powder on your blankets?

Over printing on over powdered stock is like making dough with ink as your water.
Could be why its not drying.

Take an air hose to the stock or dust the stock through the press on impression.

How ever it does sound like you're printing over a varnish or coating.

Fill us in on what worked for you.