Calcium and its effect

The U.S. paper industry’s switch from acidic to alkaline paper, coupled with an increase in

 the pH and alkalinity of municipally supplied water, has created a new set of problems for

 today’s printer. Many of these problems can be directly traced to the increased presence of

 calcium in the printing environment. This write-up will address:

• Describe these new problems and how they can be recognized

• Recommend steps which the printer can take to minimize their effect;

• Cover the sources of calcium, and why paper an water are changing’ and
• Discuss the role that fountain solution can play in minimizing calcium’s effects.
• What are these new problems and how do they show up in the print shop?

 Rollers
  

A uniform white haze develops on the surface of rollers in either the inking or dampening 

trains. This interferes with the ability of these rollers to carry uniform ink and/or water films

, and leads to poor ink transfer, roller stripping or sensitive water rollers.

• In extreme cases, a hard band of white calcium compounds builds up at roller ends, and roller settings cannot be properly maintained.

Plates

Calcium compounds that deposit in the grain may lead to plate sensitivity (toning) that cannot

 be eliminated by increased water metering speeds or use of alkaline plate washes.

• Calcium compounds that deposit around or on plate surface dots can lead to plate blinding, where the image area will not accept ink.

 Blankets

Calcium deposition on the blanket surface (a white haze which cannot easily be removed by plain water) interferes with the ability of the blanket to transfer ink properly and print a shop dot with clean background.

 Water System

Fountain solution in pans, chiller or recirculating tanks may turn a milky white because of the 

presence of large amounts of insoluble calcium compounds. Conductivity and pH may both 

rise dramatically due to contamination and destruction of the buffer system. The pressman 

may not be able to keep these non-image areas clean despite increased water metering 

speed.

• White or off-white deposits may accumulate in the bottom of press fountain pans that have 

poor drainage or exchange rates, reducing their effective volumes and possibly leading to 

fountain pay overflow.

 How can the printer minimize these problems?
• It is important to realize that not all alkaline paper and board is bad, and that changes in the

 water supply can be easily dealt with.

• The most important thing is to recognize the above symptoms so that no time is lost in 

implementing a solution. We can’t change the paper or incoming water supply, but by

 following these recommendations the printer can minimize the impact of increased calcium 

on his process.

Water The use of a Water Processing System ensures a consistent supply of water designed specifically for the printing process. Other treated water sources have drawbacks:

• Reverse osmosis (RO) water is very aggressive

;

• Distilled water is very expensive; and

• Softened water still contains undesirable alkalinity.

Reservoir Maintenance

Recirculating tanks should be drained on a weekly basis and refilled with fresh fountain

 solution. At this time, press fountain pans should be cleaned if needed.

Printers should monitor and record both pH and conductivity on a daily basis. If pH goes 

above 4.5 or if conductivity increases 1000 ųmhos above initial readings, consideration 

should be given to replacing the solution regardless of age.

Periodically or as needed, the entire recirculating system should be drained and then flushed 

with either bleach/water solution or a maintenance product to remove all contamination.

Fountain Solution

We’ll discuss them in more detail later. Normally, fountain solutions are selected based on

 water quality and type of press and dampening system. Type of stock may influence the 

choice, and in some cases a switch to obtain great buffer capacity may be necessary.

Press Maintenance

The importance of a regular press roller maintenance program cannot be over-emphasized

. Roller maintenance products such as Salt Deglazer, Salt Crystal Remover and Alkaline 

Paper Roller Rinse are designed to remove calcium compounds from the roller train. 

Metering Roller Cleaner (MRC) and Chrome Roller Cleaner (CRC) will clean and desensitize 

rollers in the dampening system.

Remember that most calcium compounds are essentially insoluble in water and alkaline plate

 cleaners. They are actually insoluble in acid-type fountain solutions as well. Calcium 

carbonate slowly reacts with the acid to yield calcium ions, which can combine with other ions

 such as citrate and phosphate, and precipitate out on rollers as a white haze or as hard, 

rock-like deposits.

Now that we have described the problem and how to minimize its effects, let’s discuss the

 sources for calcium in today’s printing environment, and how they contribute.

Water

All municipally supplied and well water contains at least some calcium. The amount can be

 determined by a very simple water hardness test. This test, however, does not measure total

 alkalinity, which is more important when selecting a fountain solution.

Carbonate, which is alkaline, is the species, which actually reacts with the acid in the fountain 

solution, raising its pH and using up buffer capacity.

Conductivity usually, but not always, increases as hardness and alkalinity rise.

These three properties – conductivity, hardness and alkalinity – are independent. A properly

 conducted water quality analysis always includes all three along with a pH determination.

Ink

It is well known that press units printing red inks tend to develop more calcium-related 

problems. Fountain solutions in these units may also experience sharp upward rises in pH

 and conductivity within a short period of time. Many red pigments in inks are calcium-based

, and the constant mixing of fountain solution and ink on the press causes some of this 

calcium to be “leached out” by, and absorbed into, the fountain solution. Once there, it is free 

to react with other ions that are present, and can form hard, insoluble compounds.

Paper

In the last decade, most  paper manufacturing has switched from an acid to an alkaline

 process. This is a less polluting, cheaper process that produces a better printing sheet that

 is more permanent. But it is also a process that introduces calcium carbonate into the 

printing environment.

Very simply, paper consists of wood fibers, inorganic fillers and a material called sizing, 

which acts like a glue to hold the insides of the sheet together. Coated paper, of course, has

 an outer layer, generally starch-based or latex-based, which also contains fillers.

Acid type paper uses 8% to 12% clay (an alumino-silicate) as the main filler along with a 

rosin-alum sizing. For this to function effectively, a pH of 4.5 to 5.5 is needed which results in

a sheet with a residual acidic pH (acid paper). Calcium carbonate can’t be used because it 

would dissolve and cause foaming.

Alkaline paper, on the other hand, is made under slightly alkaline (pH 7.5 to 8.5) conditions,

 uses an organic sizing, and accommodates higher amounts of filler – usually 15% to 25% 

calcium carbonate.

Improper or insufficient sizing and/or poor coating can lead to piling and the release of

 calcium carbonate onto the blankets. Then, it can work it way back into the ink and 

dampening roller trains via the plates (remember, all these items are in continual high speed 

contact). Part of the fountain solution’s job is to absorb this calcium carbonate. If too much 

comes out of the paper, the excess ends up on the rollers, plates and blankets.

What role can fountain solutions play in minimizing calcium-related problems?

A wide variety of fountain concentrates for both soft – to – medium and hard waters. Water 

that contains large amounts of calcium and/or alkalinity (generally 200 ppm or more) requires

 use of a fountain concentrate with extra acid (a sol-called “hot” etch); otherwise the starting

 pH will be too high. Carbonate alkalinity reacts with the acid in the fountain concentrate, 

raising its pH.

All modern fountain solutions contain a buffer system, which is designed to react with or 

absorb alkaline materials and maintain a constant pH. Buffer capacity differs from solution to 

solution, and sometimes a change has to be made to a solution, which has larger capacity.

Even if the printer has soft – to – medium water, either a “hot” or highly buffered fountain 

concentrate may be necessary, especially if he is printing large amounts of very alkaline or 

poorly sized paper which has poor water resistance. This type of paper may release more

 than the normal amount of calcium carbonate into the fountain solution.

Due to recent government legislation (EPA lead/copper rule), municipalities are raising the 

pH and alkalinity of tap water to combat corrosion and the resultant increase of lead and 

copper in drinking water. Depending on the magnitude of these adjustments, a change in 

fountain solution may be needed.

Optimize Your Performance

We have seen how recent changes in paper manufacturing and municipal water supplies

 have resulted in calcium-related problems becoming more prevalent in the printing 

environment. We have also seen that these problems can be easily minimized through 

regular pressroom maintenance and by choosing the correct fountain solutions, press

 washes and water processing system that addresses the needs dictated by the local water

 supply and printing application.