Glycols & their effect on drying, scuffing & rub resistance

[Lukew]

In our bid to eradicate alcohol from the pressroom we have tested a range of fountain solutions.
Some have contained in concentrate 1% - 3% glycols others 5% - 10% glycols others 45% - 70% glycols.
Using the same ink set what we have noticed is that the higher the glycol level in the fountain solution worked out via the concentrate level then the mixed fountain solution glycol level. There becomes an issue with drying, scuffing & rub resistance.

It seems on polyester plates running alcohol free with standard ink sets need a certain % of glycols to effectively clean the plate and keep it running clean. It's a shame low level glycol founts don't work with standard inks as the jobs dry significantly faster.
Is there anyone out there that has worked out the approximate % level of glycols that can be in the mixed fountain solution before there is a detrimental effect on drying, scuffing & rub resistance?

 

[Bob Peterson]

Lukew

From my experience, in order to maintain an inks oxidation/dry time and rub resistance, the glycol content of the fountain solution should below 2%. The glycol content can be measured by a brix refractometer. (Low cost Brix refractometer with ATC 0 to 10 Brix - Brix Refractometers from Cole-Parmer)

My recommendation is that you test different 1 & 2 step solutions. What we normally see, that maintains the inks properties and provides optimal print quality, is a one step mixed at 5-7 ounces per gallon. Or, a two step mixed at 4 ounces of etch and 1.5 ounces of sub per gallon.

All of the above is dependent on the type and consistency of the incoming water, i.e (Tap or Reverse Osmosis). R.O water is the best as it remains consistent providing the system is maintained properly.

Bob

 

[Lukew]

Thank you for that info. I will look at purchasing that instrument.
From my calculations our current fount would be below the 2% glycol limit when mixed but the drying, scuff & rub resistance is significantly worse then mixed founts that contained less then .5% glycols.

If 2% is the limit, then would .5% - 1% be the ideal level?

Regards...

 

[Bob Peterson]

Luke

Ideally, the best mixture is the one that allows you to run the least amount of water on the plate, while keeping the non image area clean. If you can achieve this with .5-1.5% glycol content, that would be ideal. However, if you can't keep the plate clean with out increasing the glycol and/or the amount of water on the plate, I would recommend trying a different etch and/or sub until you can achieve the desire effect while keep the glycol and water setting to a minimum.

Keep in mind, the more water you have to run along with a glycol content above 2%, will create the problems you are experiencing.

Regards,
Bob

 

[RGPW17100]

Van Son makes a dryer stimulator to add to the water. You might want to give that a shot. Could not hurt