Dampening solution

[mantman]

Hello I was wondering when (and if) you mix dampening solution out of water tank what percentage you use.

10 liters=300ml fountain solution (3%), 700ml IPA (7%), rest tap water.

I aim for 5-7% of alcohol content at 10 C, with 4,5 pH, conductivity is for now unknown.

Also what is your opinion on distilled water?

 

[Joe Burger]

Hello, in some case we can use a mixture between fresh water+destilled water, if the hardness of the fresh water is too high. (16-23dH)
But first of all you have to messure hardness and conductivity. Better is to have a empty tank (20l) and the mixture is as follow.
20liter means 20.000ml total liquid
3,5% of 20.000ml = 700ml Aditiv solution
8% of 20.000ml = 1.600ml Alkohol
-------------------------------------------------
20.000 - 700 - 1600 = 17.700ml Fresh Water / you put all together in one small tank. The pH should have a value between 4.8 to 5.2 and mostly we try to fix it on 5.0pH.

 

[mantman]

Thank you for reply,IPA should be 5-8% at water tank 10 Celsius or room temperature?

 

[Joe Burger]

The value of Alcohol its depend on several different issues. (9,5°C to 11°C temperatur)
Generally, the additive what is in use it depends on the product. In most cases, and if the Additiv is not a ´less-alcohol-additiv´ an alcohol content of 8% is sufficient enough. However, in some cases 10% of Alcohol may be necessary if the rubber rollers in the dampening unit are very old.
If you tell me more about the machine, -typ you are working with?

 

[mantman]

Speedmaster 52 so it's alcolor dampening system. My issue is I get a small toning at gripper edge mainly at 1st PU and from time to time at 2nd too. When i increase water it goes away but i think it gets too much water (40% pan) rollers are brand new (westland) and in spec of stripes so it must be chemistry or plate (processless Kodak)

 

[Joe Burger]

Then, go up to 10% Alcohol and what you can try, (regarding the KODAK processless plate), check the value at ´Pre-Dampening-Menue´. Means, the turnment of the fountain-form-roller when you start production and when it runs with 100% of speed during pre-dampening of the plate. It should have 8-12 turns when printing starts. But, however, in case of stripe at gripper edge, first of all check ink-form-roller setting.
At Speedmaster 52 and its ink-form-roller, it is possible to let them move left to right, or the rollers are fixed, without movement. Check this out first and that they don´t have a ink-strip at plate with 4mm. Better is ... roller: whight=3.5 / blue=3.0 / red=3.0 / yellow=2.5mm

 

[mantman]

Ink stripe on paper happens after a while of printing. As for plate stripes tou recommend, I don't know it reminds me of GTO stripes . No end play of rollers