I want to know what is the relationship between the viscosity of the fountain solution and additives maybe added to it and what is the most important factors which determine viscosity of fountain solution booth alcohol and alcohol free...thanks
when you say viscosity do you mean measuring the speed of a set volume through an apature whilst timing it, if so there will be a change depending on the aditives but to what degree? and if the results are acceptable and repeatable? i would guess that the results would be crude at best without gaining and acurate data to use on press or in the lab, i believe that more info would be gained by using surface tension angles. but anyway a simple answer is alcohol or ipa adds to viscosity whilst im not sure fount does, i know fount soloution effects specific garvity but at a guess fount aditives would not change viscosity that much.. im ready to be shot down though.
P.S Heres a web adress which has the quote about IPA ading viscosity so you can cite it.
Are you guys sure you aren't lloking for the Surface Tension of mixed founts? The Dynamic Surface Tension is actually a calculated number to determine "How Wet" a particular diluted fountain solution is. The lower the number - the wetter it will run.
Examples are as follows: Typically Heatset Web founts run "Wetter" than sheetfed founts to keep up with the speed of the press. Adding 99% Isopropyl Alcohol to mixed fount makes the fount run wetter. That why water speeds get reduced by adding it to the mix..
Don't confuse how wet a fount runs with the densitiizing of the product.
Your supplier should be able to give you "Surface Tension Numbers" or at least ranges in what the product will be.
For measuring fountain solution viscosity you might want to use an Ostwald flow viscometer. I did a lot of viscosity related research on fountain solution back in the early 90's and this was the only device which gave reliable or useful results.
I do think that the FS will be more or less Newtoninan fluids, that is to say it will not depend on shear put on it. The same should apply if you put IPA in the FS. The small amout of additives will probably not have a big inpact on the viscosity. Where the absolute value lies I am not certain but likely very similar to water (1 mPas).
Fountain solutions are essentially pseudo-plastic or non-Newtonian fluids. What this means is the viscosity of the fountain solution is reduced by shear but recovers when the shearing force is removed. What this means is that attempts to raise fountain solution viscosity usually have little or no impact on the rate at which continuous dampening systems move fountain solution from the pan to the plate, due to the shearing force exerted by the dampening system.
We went Alcohol free on just one machine and when we were satisfied all presses went on it.
One other things I noticed was the temperature played a big part with the system.
and the alchol substitute has a buffer on it which stops it going too far.
I also noticed when the water in the tank started to turn a slightly milky was pretty close to the mixture required.
The temperature in the main tank was running about the 12c and by the time it reached the press it was 17C on the way back to the tank so you are looking at 15c to 17c on the press
The only problem was the blanket wash kept getting into the main tank and you have to keep changing
The filters on a regular basis
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