white specs when backing up a four color solid job

[jms]

i am running a four color solid black job. the first side runs really good and clean with no hickeys or specs.
the job is set up as a work and turn and when i back it up i get alot of white little specs everywhere.
they are not in the same spot they come and go in different areas of the sheet. no two sheets have it in the same spot i am running a mitsubishi 6 color 40 inch.
stock: 100 lb. dull book with satin a.q.
please help...

 

[Kaoticor]

What are the white specks? Are they nothing being printed there, or is the paper picking off of the sheet?

 

[jms]

What are the white specks? Are they nothing being printed there, or is the paper picking off of the sheet?

Both sides of the sheet print nice as long its a one side but when I back it up they show up...it's a 4 color solid black.

 

[Bob Peterson]

When you say it's a 4-color solid black, are you referring to it being 400% TAC? Or, is the black a build?

Either way, from your description, it sounds like your getting picking on the back up. How long have you let the job sit before backing it up?

 

[jms]

I let it sit for about 20 mins..... But we always back it up right away...

 

[RGPW17100]

Try running the back side first. What I mean is flip the paper over before you run the first side. You may be seeing a printing issue of wire side versus felt side.

 

[tkemerly]

Might want to check spray powder unit. (Some folks call them powder bombs)
You might try turning powder down as far as able and run small lifts.
Have seen small droplets of oil and water blowing out of air lines (Sheet hold-downs) throughout press line. Water or oil can do something similar making it hard for the ink to get to the sheet but disappears by the time you see it.
Anyway...

 

[tkemerly]

It as well sounds possible that the water base coating is not completely dry and it is gassing off a bit causing the sheets to stick together thus pulling the ink off. May see some evidence on the backs of the sheets.

Most folks will run powder at a very minimum (No powder clumps) on the first pass and if able, wet plate / Dust the sheet on the second pass if they have a unit open before it gets ink again. If no unit is open they end up washing blankets a lot....

 

[jms]

Well the problem was fixed just by changing to another drum of satin coating, I don't understand why that had anything to do with the second side but it took care of the problem..
Thanks for all you suggestions.