Exothermic reaction after printing (old songs about the main thing)

Tatyana

New member
I found few old topics about exothermic reaction after printing: different types of paper, inks, fountain solutions with and without coating and so on. Quite interesting information about linseed oil and vegetable oil-based inks. If I am not mistaken the main idea that there is a chemical reaction between paper and ink. I would be very appreciate if you share new information about this problem. For example, when you last time faced with this problem and how it was solved (if it was…) and what was the reason in your opinion. In my practice a have had different cases but i still have no clear version of what it is.
 

cementary

Well-known member
Well of course it's chemical reaction - oxidation to be particular. The main idea is something makes the reactiom more aggressive in one cases (say next morning after printing pile temperature already around 40 c), or if paper is thick and pile is high, then the heat generated from polimerization process has no place to go and temperature rise over time. Especially if printed 4/4 in one run - twice as much heat in the pile.
Particular paper can be the cause for, and i'm pretty sure that you ink supplier will stand to it.
From my experience it's always Huber ink with different papers.
 

cementary

Well-known member
I am for sure do not think that way. In fogra reports on ghosting btw they didn't mention significant temperature rise anyway
 

turbotom1052

Well-known member
Have you never noticed how a pile pulled from the delivery, and sitting off to the side, will often rise in temperature in comparison to the freshly delivered pile? I believe that this temp rise has a pretty direct impact on gas ghosting as well as blocking. This is one of the reasons that on a form that shows a good potential for gas ghosting, can often be lessened by a good winding BEFORE pile temps have a chance to build a bunch of heat. This winding will also help in preventing blocking but not nearly as much as it helps gas ghosting. Its been my experience that blocking often happens before you even roll the load out of the delivery.
 

cementary

Well-known member
@turbotom1052 , in case you're not mixing terms set-off and actual blocking, i believe you're talking about different problem. @Tatyana referres to radical oxidation with probably reverse polimerization after printing in terms of days, not right after printing.
Winding is helpful against gloss ghosting, also as small piles are. Anyway glass ghosting is result of polimerization which is oxidation, which produce heat, but not that much
 

turbotom1052

Well-known member
isn't blocking nothing more than an extreme case of setoff? ive seen both happen while the pile is still on the delivery platform.
 

cementary

Well-known member
Yepp, i've seen too, but these are different problems. If you see these right in the delivery, then there should be other factors like inappropriate use of ir-light, lack of powder or wrong size, exaggerated ink densities, too much fointain or too much area coverage - legions of factors btw. But in case for this topic non of these factors are relevant because temperature rise happens way after the delivery, sometimes even with the cut and sewed product, right before shipment
 

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