What is fountain solution?
The dampening system on a lithographic sheetfed press applies a water-based dampening or fountain solution to the printing plate before it is inked. Dampening solutions keep the non-image areas of a plate moistened so that they will not accept ink, and are applied to the entire plate.

The non-image areas of the plate, which are made that way by adsorbing a thin film of gum arabic to them during platemaking, are hydrophilic (water loving) while the image areas are hydrophobic (water repellent). The desensitizing film on the non-image areas wears off gradually as the plate continues to run on press, so the chemicals in the dampening solution replenish the desensitizing film. Ink, plate, press speed, paper, temperature, and relative humidity are the principal factors that influence the need for various dampening solutions.

Fountain Solution
Fountain solution is a water-based mixture specially formulated to dampen lithographic printing plates before they are contacted by the inking rollers. In concentrated form, it is commonly referred to as fountain concentrate, fountain etch, or just etch. Most fountain concentrates today contain synthetic desensitizers. Very few manufacturers still use natural Sudanese gum arabic because of its cost. The term dampening solution is used for the diluted etch.

Fountain Solution Ingredients
Fountain solutions are usually sold as concentrated solutions that are diluted with water to the proper concentration. Most one-step concentrates already contain a natural or synthetic gum, an alcohol substitute, and other essential ingredients, and simply require being diluted with water. With two-step concentrates, the first step generally contains all of the ingredients except the alcohol substitute, with the alcohol substitute added as part of the second step. Although this extra step might be an inconvenience, it permits the press operator to control the alcohol substitute concentration better.

The proper mixture of chemicals in the solution is critical for quality printing. Though there may be many chemicals that make up a given manufacturer’s dampening solution concentrate, the general ingredients common to most are described below.

Composition of a Fountain solution
Fountain solution composition varies for a number of reasons. Most dampening solutions, however, are acidic, with a pH of 4.0-5.5 being typical. The dampening system itself also influences the composition of the dampening solution. For example, some dampening systems require a specific percentage of alcohol (or alcohol substitute) due to the method of applying the solution to the printing plate. Sometimes, in a conventional dampening system, the use of such an additive improves print quality although its presence in the dampening solution may not be essential.

In general, a dampening solution will consist of the following ingredients:

• Water, with minimal impurities.
• Acids or bases, depending to a large extent on the ink being used. Acids used include phosphoric acid, citric acid, and lactic acid.
• Gum, either natural (gum arabic) or synthetic, to desensitize non-image areas—that is, to make them prefer water to ink.
• Corrosion inhibitors, to prevent the dampening solution from reacting with the plate. Magnesium nitrate is sometimes used; it also acts as a scratch desensitizer and buffer (a substance capable of neutralizing acids and bases in solutions and thereby maintaining the acidity or alkalinity level of the solution).
• Wetting agents, such as isopropanol or an alcohol substitute, which decrease the surface tension of water and water-based solutions.
• Drying stimulator, a substance—such as cobalt chloride—that complements the drier in the ink. Drying stimulator is an additive that is used only if ink is not drying fast enough. Typical concentrations are 1-2 oz. of stimulator per gallon (8-16 ml per litre) of dampening solution.
• Fungicide, to prevent the formation of mildew and the growth of fungus and bacteria in the dampening system.
• Antifoaming agent, to prevent the build-up of foam. Foam can interfere with the even distribution of dampening solution on the dampening rollers.

What is pH?

• It measures the acidity or alkalinity in a solution
• The pH scale goes from 0 to 14, with 7 being neutral.
• A pH lower than 7 is acidic
• A pH higher than 7 is alkaline, or basic.
• Measured on a logarithmic scale, for example:

pH 5 solution = 10 X more acid than a pH 6 solution pH 4 solution = 100 X more acid than a pH 6 solution

What is conductivity?

• A solution’s ability to transmit an electrical charge; to measure conductivity, one measures the number of ions in a solution. The higher the ion concentration, the higher the conductivity degree.

I hope this has given you a good overview of the necessary parts in a good fountain solution, and I leave you with some of the advantages of modern fountain solutions: prevention of printing plate surface oxidation; prevention of foaming in printing fountains and in dampening systems; curing of micro scratches on plate surfaces; lubrication of blanket surface; resistance to change of acidity in fountain; formation of protective film on plate surface; clean roll up; and minimum start up waste.