Previously we touched on how fountain solutions help maintain pH and conductivity during press runs. Some printers are knowledgeable about both these values. However, many printers are only familiar with pH, but don’t measure or understand conductivity.
Quick chemistry lesson here. pH is simply the amount of acid present in the fountain solution. Acid helps the ink stick to the image area and keeps the non-image clean. Conductivity is the measure of electrical flow through the fountain solution.
Pure water does not conduct electricity well, so as impurities from ink, paper, spray powder, and paper coating increase, so does conductivity. The higher the conductivity, the more problems you are likely to experience. If you use tap water instead of RO or distilled, you are adding a lot of minerals and other impurities that will increase conductivity and shorten the life of your fountain solution. That’s why it’s so important to start with RO or distilled water, and to measure both pH and conductivity.
Let’s start with a simple scenario. Your press is running fine for the first 2-3,000 impressions or so, but then you notice the ink isn’t as dense as when you first started. You increase the amount of ink, and for a while the image seems fine. Then things go downhill again. Ink starts piling, and you’re getting a little picture framing.
To fix the piling, you increase the amount of fountain solution, but then the ink density becomes too light again. You measure pH, but it’s within range, so what could be causing the problem?
The most likely culprit – conductivity! At the point the ink starts breaking down, conductivity has become so high that it affects the ability of the solution to do its job. Now you must clean up the press, remix and replace the fountain solution. This is not fun or productive. You waste time, paper stock, ink, and sometimes your sanity!
It’s relatively easy to measure both pH and conductivity. There are a lot of good meters on the market.
Measuring conductivity is a little more involved, but it’s not difficult. Take measurements of the water before and after mixing your solution. Write this number down as it is your starting point. Some solutions might have a reading of 1000-1200, but some may be as low as 600 depending on the type of surfactants, the addition of alcohol or alcohol replacements. This is not a big deal. It’s your “norm”.
Measure conductivity every hour or so and record the numbers. Problems most likely will start when conductivity gets to be 500 -1000 points higher than where you started. (300-400 if your solution starts out in the lower 600 range.) Each press is different, so measure each one. Once you notice conductivity is creeping up too high, replace the old solution.
Burnishine fountain solutions are formulated with excellent wetting agents and buffers that will help keep your press running smoothly throughout the day. Just remember, the longer the press runs, the more likely it is your solution will become contaminated. Measuring conductivity will save you a lot of time and money in the long run.