Conductivity issue?

[AMCguy]

I know this has been posted before but...if straight water is at 900 to 1000 what would be a good start? We are running at 3400 now right out of the replenisher and I think that is too much, it climbs to over 4200 in the water pans after a few runs.
On start-up it takes forever to get ink on the paper even though ink is coming down the rollers...stripes are OK. Then it seems after you do get ink you are turning it back down because the density is too high.

Would that be because of such a high conductivity? PH is 7 to 7.5...we run a neutral fountain solution. We have in the past kept it at no more than 1000 over water out of the replinisher, but the boss thinks the product is cleaner with the fountain solution at 3400...I think its a pain in the A-- to run now.

Thoughts/Opinions??

 

[D Ink Man]

You need to check with your etch/fountain solution provider. There is no standard conductivity values for offset presses. It depends on the chemistry of the product and the recommeded dosage.

Have a technical fellow come into your press room and perform a titration and chart it, post it for easy access by the press crews.

There we go with that technical service thing . Somehow it keeps reappearing.

D Ink Man

 

[aqazi81]

Are you running IPA free?
This might help...
You can use the following procedure to
benchmark an IPA-based or an alcohol-free
dampening solution you’ve never used.
The relationship between conductivity and
concentration is linear, so knowing the conductivity of different amounts of dampening solution concentrate in your water makes it easy to
check the strength of your dampening solution.
To do this, you need to plot the conductivity of
your water and dampening solution concentrate
mixed together at different concentrations.
Measure and record the conductivity of your
water in a clean 1 gal (3.8 l) bottle. Add 1 oz
(29.6 ml) of dampening solution concentrate,
shake well, re-measure the conductivity, and
record the figures. Then add another ounce of
concentrate, re-measure, and record the conductivity. Repeat this until you exceed the manufacturer’s recommended dampening solution
concentration.
Plot these measurements to make your
own char ts with concentration on the horizontal
axis and conductivity on the ver tical axis. This
would give you two cur ves–one with alcohol
and the other without. Pure alcohol has little
effect on pH, but does lower conductivity.
The same procedure can be done with
alcohol substitutes. In the proper amounts,
most substitutes will have little effect on pH
or conductivity. Other dampening solution
additives may have dramatic effects.
Later, when you want to determine the
concentration of fresh dampening solution,
measure the conductivity and read the corresponding concentration from your char t.
Remember to check the water and fresh dampening solution occasionally to be sure they have
not changed. Make new char ts as needed (for
example, when changing brands of dampening
solution or after installing a water purifier).
Recommended conductivity may var y considerably with the brand of dampening solution.
In any case, it is a good idea to adjust your
solution to a conductivity that adds to the water
supply’s contribution but still leaves a reasonable operating window.

 

[Dan Roll]

You don't mention if your plates took ink quickly at the lower conductivity, but it is possible that too much fountain solution could interfere with the ability of the plate image area to attract ink, depending on the formulation of the fountain solution.
The rise is conductivity is alarming, assuming you are running a newspaper type press (based on running a neutral) as unless you have continuous dampening it is unlikely this contamination is coming from the press.
If your base reading (straight water) is 900 to 1000, the additional conductivity you get by adding fountain solution is diminished compared to running in soft water (ie, if three ounces of fountain solution would add 1500 Mmho's to RO or DI water with zero conductivity for a total of 1500, the sme addition to your water might only read 2000 or so).

 

[AMCguy]

No alcohol, water is softened with water softener only, Goss Community. Nothing on the barrel, had to do alot looking online to find it, this but here it is.



So with 1000 plain water we should be between 2350-2660moh according to the pic...still seems alittle high to me. Our pH would never get that low even with 3oz per gallon.

Did two runs now, two different nights and had ink right away on start up, in fact we where printing good copies in 600 vs 1000 to 1200+. The press is much easier to set color and maintain it. Granted it might be alittle low as I'm putting in only 3/4 oz per gallon starting at around 1600 to 1700moh mixed in the pans. But it ran clean and no toning also. Climbed to only 1800 on the Cyan after the run.
Running 2.5+ oz at 3400moh is just making the ink blind on start-up and a pain to set color. Going to try one more run before I crank it back up so I don't hear it from the boss when he comes back. I go on vacation next week anyway.

 

[BeauchampT]

Well, if running less fount works better, all the power to you!

We had a fountain solution from Huber at one time. Recomended dosing was about 3 oz/gallon or less; we couldn't get the plates to run clean unless we ran up at 5 to 6 oz/gallon. But when we did - amazing! Minimal piling, minimal feedback into the water system, etc.

A few years later they discontinued that product and gave us a related product, that had the same recommended dosing, so we figure, just go to what worked before, right? Wrong....had to drop it down to 2 oz/gallon for best results.

It seems that sometimes even what the manufacturer expects is not going to be a perfect range for you. Different inks, papers, machines, operators, climactic conditions, (and maybe the relative orbits of Mars and Jupiter???) all seem to affect fount/ink interaction. You just need to find what works and run it.

Glad you seem to have found a solution.

 

[ponnapati123]

Conductivity is indirect measure of water contamination. Conductivity goes up means contamination in water would be higher vice versa. We are maintaining conductivity in our press at 600-800 in sheetfed presses. We are using Alcohol to reduce water surface tension & PH is 4.3 - 4.7. We never experienced ink in fount solution. Try to use this method it will help you