Trap and Mottle problem

[Prepper]

We have been experiencing low trap between C and M lately and also have been having mottle that appears to be the M unit. We run KCMY sequence and the major things I know of that have changed are we switched to alcohol sub and also using some uni-tack inks now. The trap isn't always low, one side of a 3 sig job ran fine the other day but now isnt trapping well at all on the other sides? CM trap is reading 60-64%, any suggestions?
Thanks

 

[jlind]

And so, where the trapping is poor, you see mottle? That would sound like back trap mottle. The unitack inks are nice for moving a rotation around, but tack rated is always better for trapping. They count on tack to build up fast enough after printing on the coated paper for the next ink to trap as if tack rated. If you get a paper with slow absorptivity or high hold out, the tack can't increase and the ink doesn't know which way to go, to the blanket or to the paper......Now the alcohol sub is changing the tack in different ways for each color, further aggravating the situation. Printing sure is a lot of fun.
John Lind
Cranberry Township, PA
724-776-4718

 

[Lukew]

We run novavite 918 bio, inks, now their tack sequence is made so you run KCMY but we had the problem your having, magenta would not sit over cyan,, and would just mottle.
We changed our sequence to KMCY and we no onger have problems,, one bonus of that sequence, is you get richer blues, and of couse your skys look better.
worth a go...

 

[Paultheprinter]

Hi luke, i too have run novavit is kmcy sequence but got the cyan leaching into the yellow. how did you fair?

 

[Lukew]

Yeah paul, it happens a very small amount,, nothing that much that actualy effects the yellow or the job though..Mainly only if its a long run large cyan coverage..

Not sure the reasons why it won't print KCMY as that is its designed tack sequence, but from reading I've found out a few europe guys run it in the KMCY sequence too..

 

[Prepper]

Trapping

Trapping

Thanks for the help. We did try switching the sequence to KMCY but our gray balance was pretty far off then, too red? We're running G7 so to switch the sequence should we have to redo our press calibrations?

Also, since then, we've talked with ink rep and they all say he's running too much sub, 3oz, to cut it back to 1oz, he'll have to run more water but the ink is formulated to handle that. Also he is adding alcohol to the mix also and everyone has said not to do that.

Any comments?

Thanks again, and yes it sure is fun!

One other question, we are a low volume in-plant basically, we used to run alcohol and we can still if we want to because of our low volume, with that in mind and you could run either which would you choose alcohol or sub, and is it even close?

Terry