where does the heat come from?

[madjock]

I printed a two colour job last week on our old 6 col 102 which doesn't have any lamps, when I came in the next morning the pressroom seemed unusually warm, I checked the stacks of printed work and they were seriously hot.
I am guessing this is some sort of chemical reaction taking place, but can anyone out there explain the actual mechanisms going on here, and can the heat have an adverse affect on the job?

 

[Al Ferrari]

It's old news that what we loosely refer to as the drying of ink involves chemical reactions which generate heat.

 

[kyle]

You must have used warm red.

 

[GazKL440]

Global warming.....

I love the warm red reply...GOLD!!

Perhaps your pantone 123c thought it was pantone 123u and tried to get warmer....did you know they are DIFFERENT COLOURS??????

Residual press heat can also stay in paper stacks for a bloody long time... hand loading full stacks off our old 40" Roland few years back and the stock would be hot to touch for most of the load....which was nice in winter of course

Al... i must say ive never heard that but it certainly sounds like reasonable thought given the inter-reaction of the printing process... still, you learn something new every day if your willing to listen thank you

 

[Ritter]

Loads of chemistry and chemical reactions happen on the press. The drip-off varnish effect is good example of that. There are lists of inks that cannot be coated with a standard coating without reaction (generally the color changing type and not the explosive heat generating type). Talk to your ink vendor they will have loads of information for you.

On a side note a funny prank I have seen done in the shop:
A new prepress lackey was "learning" (read:chatting) by the smaller presses. The "wise" press operator explains to him that cool grey ink is cool to the touch and that warm red ink is warm to the touch. It just so happens that job in warm red was being ran and an 5lb open can was laying beside. The pressman tells the guy to touch the ink with his finger tip to feel the warmth in goes the finger and the pressman shoves the guys entire hand in the ink. The guy had a red hand for days afterward. On another occasion I found this poor guy looking for a "paper stretcher" (he had been searching for nearly 2 hours).

 

[buckeye]

Yes, but "Perhaps your pantone 123c thought it was pantone 123u and tried to get warmer....did you know they are DIFFERENT COLOURS??????" was....PRICELESS.

 

[DanB]

On another occasion I found this poor guy looking for a "paper stretcher" (he had been searching for nearly 2 hours).

We used to have folks look for a jar of halftone dots.

 

[HecTiK]

what about the blanket lube?

 

[Green Printer]

What you experienced is an Exothermic reaction. I have seen this many times. Linseed oil gives off heat when it dries. The acids in the fountain solution can help this along.

The follwoing links should be helpful

Exothermic - Wikipedia, the free encyclopedia

http://www.voc-infoex.uni-karlsruhe...atform/website/Guidelines/Printing/00dcec.pdf

http://www.hwsands.com/files/printer-friendly/eti.pdf

Brazilian Archives of Biology and Technology - Thermal and spectroscopic analyses on the molecular interaction between eucalyptus kraft pulp components and offset printing inks