Plate background toning (specks)

[GJOHN]

One of my clients is experiencing tiny specks in the non-image areasof the sheet. This is not easily visible by naked eye but under a loop, it is very obvious. One observation is that some of the non-image area show more specks than others and the black plate shows the most specks, others less. They also had some offsetting issues but it was an ink problem, changed inks and fountain solutions but the non-image area specks keep coming back. Any thoughts.
GJ

 

[buckeye]

Re: Plate background toning (specks)

How old is your chemistry? We get background toning in non image areas when our plate (Fuji LPNV2) processor chemistry gets weak. We were advised to change chemistry once a month but we sometimes have gone as long as three months and that's when the plates start to hold tone in the non image areas. The plates look clean to the naked eye but when they're on press they start scumming.

Erik

 

[upekkha]

Re: Plate background toning (specks)

i concur with Erik
do you have a hard water problem, and if so, might consider using a water-softener
we use creo/kodak PTP plates and also get that problem after about 10-12 weeks, so usually we clean out the processor after 6 weeks

 

[bikerterry]

Re: Plate background toning (specks)

From a prepress perspective, anytime the press department changes inks, fountain solutions, blankets, etc. we reprofile the presses for dot gain. I changed jobs 6 months ago to a plant that had been having the same problem with toning and specks, for about a year. They had never profiled the presses for dot gain. After that was done and the actual dot gain curves were built the problem went away.

Rampage 10.4, Screen Plate-Rite 4000, Fuji LHPSE plates, Fuji processor.