WHY TEST FOUNTAIN SOLUTIONS?
Accurate fountain (dampening) solution concentration control is essential
for consistent, high quality results in lithography. Low concentration can
cause drying on the non-image area of the plate resulting in tinting,
scumming, blanket piling etc. High concentrations, on the other hand,
bring about over-emulsification of the ink. This results in weakening of
color strength and changes in ink rheology (body and flow properties).
Correct concentration will allow the non-image areas of the plate to be
WAYS TO TEST
Traditionally, pH was the test relied on to determine fountain solution
concentration. Today, however, conductivity testing is recognized as a
much more accurate method.
Many modern dampening solutions are pH stabilized (or
buffered), so only small changes in pH are seen even when dramatic changes
occur in solution strength.
Conductivity measurement is a fast and easy test which
is more indicative of fountain solution concentration than pH. This is
true for all neutral, alkaline, and many acid type solutions.
pH is still important, however, with unbuffered acid fountain solutions,
conductivity and pH can provide valuable information. Acid fountain
solution is a mixture of gum arabic, wetting agents, salts, acids,
buffers, etc. Conductivity will tell you if the proper amount of most
ingredients are present, but pH is necessary to check acid concentrations.
pH will also determine how effective one ingredient, gum arabic, will be.
What is conductivity? Conductivity is the measurement of a solution's
ability to conduct an electrical current. It is usually expressed in
microsiemens (micromhos). Absolutely pure water is a poor electrical
conductor. It is the substances dissolved in water which determine how
conductive the solution will be. Therefore, conductivity is an excellent
indicator of solution strength.
To properly measure the conductivity of fountain
1.Test and write down the conductivity of the water used to prepare the
2.Mix the fountain solution concentrate with the water, using the
manufacturer's recommendations or as experience dictates.
3.Measure the conductivity of the mixed solution.
4.Subtract the water conductivity value obtained in step 1. This is
because tap water quality can change from day to day.
The resulting number is an accurate indicator of fountain solution
strength. Caution: because alcohol will lower a solution's conductivity,
always test solution conductivity before and after the addition of
Determining the best concentration of fountain solution is mostly "trial
and error." It can be very useful to make a graph recording readings for
every one-half or one ounce of concentrate added to a gallon of water.
Record readings on a graph with the vertical axis representing
conductivity values and the horizontal axis representing ounces/gallon.
Such a graph will help "fine tune" your system during future press runs.
For "on the spot" fountain solution tests, Myron L® handheld instruments
are fast, accurate, and reliable. Measurements are made in seconds simply
by pouring a small sample of solution into the instrument's cell cup and
pressing a button. Automatic temperature compensated accuracy and famous
Myron L® reliability have made our instruments popular in pressrooms
Even though pH usually is not the best method to check the concentration
of fountain solution, it is still very important and must be checked
regularly. The pH of acid dampening solution affects sensitivity,
plate-life, ink-drying, etc. Also, pH can change during a run if the paper
has a high acid or alkaline content. pH, therefore, must be maintained at
the proper level for good printing.
A convenient and accurate way to test pH (as well as conductivity and
temperature) is Myron L®'s waterproof ULTRAMETER™ Model 6P. All electrodes
are contained in the cell cup for protection and the 6P has a 20 reading
memory to store test results onsite. Model M6/pH also measures pH and
For continuous monitoring and/or control of fountain solution
concentration, Myron L® offers a complete series of in-line conductivity
instruments. These economical, accurate and reliable models use a remotely
installed sensor and a panel/wall mounted instrument enclosure. Most
contain an adjustable set point and heavy duty relay circuit which can be
used to activate alarms, valves, feed pumps, etc. All models contain a
0-10 VDC output for a chart recorder or PLC (SCADA) input, if required.
4-20mA output is also available.
The new 750 Series II with dual set point option has become quite popular
in pressrooms. The two set points allow a "safe zone" for controlling
fountain solution concentration.
||Recommended Myron L®
directions, checking both water and mixed solution with a
Models 4P or 6P
512M5 portable DS Meter with a 0-5000 microsiemens conductivity range
|Halftones sharpen and
highlight dots lost during run
||Check pH of fountain
solution to determine if it's too acidic
M6/pH portable pDS Meter. Ranges: 0-5000 microsiemens and 2-12 pH
|Reverse osmosis water
treatment system monitor indicates
|Test RO water quality
and verify in-line instrument accuracy
|Scum streaks across
plate after 10,000-20,000 impressions
||Check acid/gum levels in
M6/pH portable pDS Meter.
Ranges: 0-5000 microsiemens
and 2-12 pH
|Personnel unable to test
fountain solution concentration
fountain solution with conductivity monitor/controller
||758II-123 (0-5000 µS)
Ultrameter 6P, 512M5 and M6/pH are available with the useful LITHO-KIT™.
This accessory includes a foam-lined, rugged all-plastic carrying case
with calibrating solutions and buffers. In addition, a syringe to simplify
drawing samples and a thermometer for testing fountain solution
temperature are also included.