Hand Out - Roller Temperature

[Alois Senefelder]

Hello fellow Lithographers.


A PDF handout, I hope you will find of interest.



Regards, Alois

 

[BeauchampT]

Not to mention the beauty of condensation and your ink rollers deciding to shred to pieces on the run.

 

[Deleted member 16349]

Hello fellow Lithographers.


A PDF handout, I hope you will find of interest.



Regards, Alois

This brings up the fundamental questions.

The PDF states some factors that can be true observations on a conventional press but they are not fundamental factors.

A fundamental question related to the ink transfer process would be something like this.

If the amount of ink transfer to the paper changes, where does the difference in the amount of ink come from?

In the printing industry, there are a lot of comments about causes of ink transfer. The implication is that one is supposed to just accept that the difference in the amount of ink just magically appears or disappears in the system.

This view of ink transfer factors is not just limited to the observations of press operators but is commonly seen in the body of knowledge in the scientific community in the printing industry. The view is not totally wrong but it must be viewed in the context of the steady state conditions of the system of a particular problem.

Much technical work has been presented related to the interfacial factors between ink and paper etc. that is supposed to govern ink transfer but much of this work is done without the total process being considered.

For the offset process, the idea that the interfacial factors somehow control ink transfer is proven wrong every day by every press operator in the world. All an operator has to do is increase the ink feed and more ink gets transferred.

 

[Dan Roll]

Anyone who runs their ink train at 25-28°C (77 to 82°F) risks (in a big way) dew point issues. When the roller surface temperatures are lower than the dew point, and here I am not referring to the dew point where humidity in the air will condensate, but the temperature at which the fountain solution will condensate out of the ink, stripping will be the inevitable result. This is epidemic amongst owners of newer sheetfed equipment that came with ink train chill systems. These people complain of stripping, but will refuse to turn their chill units off. I have heard "we turn the temperature down until the roller sweats, and then turn it up till it stops, so we are OK" over and over from people who have stripping issues, or that some expert told them to run at a magic temperature (not much agreement as to what this is) but when you suggest just turning the system off, it is like you have suggested sacrificing their babies. Recently I have been dealing with a printer who can not figure out why their stripping is confined to one press (the others do not have chilled ink trains) even though he is running at a temperature suggested to him by a salesman! Why sheetfed operators (whose presses rarely approach web make-ready speeds) feel the need to run at temperatures twenty degrees cooler than most people would run a high speed web press ink system is a mystery to me.

 

[Alois Senefelder]

Roller Temperature again !

Roller Temperature again !

Hello fellow Lithgraphers.


Part # 2 of Roller Temperature, again I hope you will of interest.


Regards, Alois