Printing Units Troubleshooting - Mottle

Definition:  Mottle is caused by paper that is either linting too much onto the blanket, or a density that is too weak, causing the solids to look weak.

Problem:  Blankets need washing.
Solution:  Sometimes an automatic blanket washing system does not do enough.  Shutting down and scrubbing the blanket with water is sometimes necessary to remove all the lint buildup on the blanket.  This buildup causes solids too look like it has flakes in it.

Problem:  Poor blanket to blanket or plate to blanket pressure.
Solution:  Poor transfer can cause piling buildup which can effect how the solids looks.  Proper pressure can help prevent paper from building up on the blanket.  Check blanket heights, plate heights and bearer pressures.

Problem:  Insufficient water flow.
Solution:  Running the absolute minimum water is a purists ideal goal of ink and water balance.  However reality dictates that a little more water is necessary to prevent piling (from paper or ink) from building up on the blanket.

Problem:  You have crappy paper.
Solution:  Spend and extra few dollars and buy a decent paper.  It will pay dividends in other ways that will save you downtime and waste.

Problem:  Poor ink density.
Solution:  Increase your density.  This isn't as much of a solution as it is a band aid.  

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