The 14th INTERNATIONAL DAAAM SYMPOSIUM “Intelligent Manufacturing & Automation: Focus on Reconstruction and Development”, 22-25th October 2003


Gojo, M.; Mahovic, S.; Agic, D. & Mandic, L.

Abstract: Paper with its properties and the way of producing in the process of offset printing changes properties of fountain solution. This is especially in respect with newspaper paper, where of reasons of alkaline paper production process and its composition and structure, pH value in the printing process significantly changes. Except pH value electrical conductivity and surface tension changes, as well other physical-chemical parameters. Investigations in this paper covered physical-chemical measurements of fountain solution in dependence on the quantity of newspaper printing paper, as well interacting time of the paper to the fountain solution. The results show that the addition of paper to the solution raises all physical chemical parameters. The wetting process is carried out in a mild acid media, in a pH range 4.4 to 4.9. Increasing pH value above 6 could cause a permanent damage of bemite Al2O3 structure that forms nonprinting elements, and that could cause changes in nonprinting elements structure and change their hydrophility. The increase of surface tension and contact angle of the fountain solution could cause significant changes in physical-chemical properties. These changes are evident in disturbing the emulgation ratio and the ink-water ratio.

Key words: contact angle, electrical conductivity, fountain
solution, paper, pH value, surface tension


The offset printing is based on various physical-chemical properties of printing and nonprinting elements. Printing elements must obtain hydrophobic properties and nonprinting elements hydrophilic properties. The selective adsorption of molecular various composition and properties are obtained. The way of paper manufacturing and in the offset printing process changes properties of the fountain solution. That is very expressive in newspaper printing where rather alkaline paper changes pH value and electrical conductivity of fountain solution during printing process. Other physical-chemical parameters could also change, which can influence the final product.


Physicochemical parameters, that greatly influence the whole printing process, are pH value electrical conductivity and surface tension. The narrow area of pH value is caused by corrosion stability of the bemite structure Al2O3 as the material forming the non-printing areas, steel parts and chromium coatings on the machine parts (Pourbaix, 1966).
As already mentioned, the newspapers paper contains notable amount of basic salts that change pH value, electrical conductivity and surface tension. It is possible that interactions guide the offset plate surface in unfavorable pH range where structure changes can occur and overall properties as well.
By measuring electric conductivity, it can be obtained the increase of electric conductive particles (anions and cathions).
Conductive particles are formed primarily by dissociation of salts for hydrophilisation and buffer system from the fountain solution and dissociation of dissolved salts that were extracted from the paper that was in contact with the fountain solution as well as dissociation of salts dissolved in water, which is used for fountain solution preparation (Mahovic et al., 2003). Except the influence on damping of the printing plate, pH value considerably influences the oxypolymerization, viscosity, tackiness and tinctorial strength of the ink as well as corrosion of the machine parts.
By measuring the surface tension of the sample, the influence of the surface active substances from the original concentrate on the systems of the fountain solutions as well as on the mixing and emulsification of ink, have been observed. The basic role of the fountain solution is the qualitative damping of the nonprinting areas.
All above mentioned physical-chemical parameters influence directly or indirectly the damping of the printing plate (Lovrecek et al., 1999).


The influence of quantity of paper on electrochemical parameters changes of fountain solution that was prepared by diluting of concentrate by demineralised water in volume of 2.5%. Defined amount of paper (45 gm-2) in the quantity of 0.02, 0.06 and 0.1 gcm-3 was dipped in fountain solution. The samples of the fountain solutions were prepared by diluting the original concentrates with the demineralised water in concentration of 2.5% vol.
Electric conductivity of the fountain solution sample was measured by the conductometer LF 330/SET by WTW GmbH. pH values of the sample were measured by pH meter 330/SET from the company WTW GmbH with standard electrode with previous calibration. Surface tension of the prepared samples was measured by the stalagmometer method.
This comparative method measures indirectly the mass of the drop sample in comparison with the sample of the known surface tension. The density of the solution was measured by picnometer.
The distilled water with the surface tension 72.75x10-2 mNm-1 at 21°C was used as the reference solution. The contact angle was measured with goniometer NRL C.A. model N° A / 1000 with Rame-Hart. The solution samples were measured by means of the immersing method (Dragcevic et al., 2002).


Measuring of mentioned physical-chemical parameters show notable changes in comparison of parameters measured excluding the paper influence. The increase of measured values of fountain solution could have a negative influence on printing results.
Increase the fountain solution pH over 6 could occur a permanent damage of Al2O3 bemite structure that form nonprinting element
(fig. 1).
The increase of electrical conductivity by particles dissolved from the paper generates increase of surface tension and the contact angle as well. This causes poor wetting and toning of the print that is a negative phenomenon in the printing process.
The increase of conductivity causes increase of surface tension, that influences inadequately or poor wetting of free surfaces (fig. 2).

Fig. 1. Dependence of the pH value and surface tension on time.


Comparing the dependence of pH value and contact angle with the paper mass it could be mentioned that additives from the paper dissolve and increase pH value by simultaneous increasing the contact angle. That is very visible in first fifteen to twenty minutes of influence of paper on fountain solution. The increase of time of paper influence on the solution the concentration of dissolve particles rises, but there is a significant distinction between the paper quantity and dissolved particles. The amount of paper over 0.06 gcm-3 does not express significant increase of pH value (fig. 1) neither electric conductivity. The reason for that fact could be building of saturated solution, where is no further dissociation of salts present in the paper.
Surface activants added in fountain solution cause decrease of surface tension (Taber, 1996). The electrical conductivity depends on the variety of ions that carry the electrical charge. So, the electrical conductivity increase caused by conductors dissolved from the paper increase the surface tension (fig. 1), and the increase of contact angle as well, that result by poor wetting of free surfaces on printing plate (fig. 2).

Fig. 2. Dependence of the pH value and cos of the contact angle
on mass of paper.

During the wetting period the molecular layer that increase the adsorbance of water molecules is restored by salts contained in fountain solution. Except that salts for hydrophilisation, the surface active agents (PAT) are added for decreasing the surface tension of water (such as alcohol, carboxy-metile cellulose, diethyl glycol, propylene, glycerol, etc.).
The quantity and sort of PAT additions into the fountain solution physical and chemical properties are significantly changed. Particles dissolved from paper could influence PAT as well added salts for hydrophilisation. Measurements show that the breaking of pufer action can occur, and that negative influences on the nonprinting parts of printing plate.
Increase of paper quantity in prepared fountain solutions raises all physical-chemical parameters (except contact angle on printing elements). The reason for that behavior is dissolving of fillers from the printing paper, and various particles from paper manufacturing, for new and for recycled paper as well.

Fig. 3. Dependence of the surface tension and cos of the
contact angle on mass of paper.


The results point out that addition of paper in fountain solution increase all physical-chemical parameters. The concentration of dissolved particles from the paper in the fountain solution rapidly increase in the first fifteen to twenty minutes.
The addition of paper over 0.06 gcm-3 does not show a notable change of parameters. The reason for such behavior could be forming of saturated solution, with no further dissociation of salts from the paper. The wetting process take place in a slight acid media, pH ranges 4.4 to 4.9. Increasing the pH value of the fountain solution over 6 can permanently damage the bemite structure of Al2O3 that form nonprinting elements, and change their hydrophility.
Increasing the surface tension and contact angle in the fountain solution could significantly change their physical and chemical properties. Those changes take place in emulgation ratio and water-ink balance disturbing.


Dragcevic, K.; Gojo, M. & Agic, D. (2002). Investigations of Physicochemical Properties of Fountain Solution in the Function of Printing Quality Prediction, Proceedings of 13th International DAAAM Symposium, Katalinic, B., 141-142, ISBN 3-901509-29-1, Austria, October 2002, Daaam Int., Vienna
Lovrecek, M.; Gojo, M. & Dragcevic, K. (1999). Advances in Printing Science and Technology, Vol. 25, United Kingdom, 1999, Pira International, Surrey
Mahovic, S.; Dragcevic, K.; Agic, D. & Gojo, M. (2003). Paper Influence of Electrochemical Parameters Changes of Fountain Solution, CD, 2nd Day of Electrochemistry, pp. 59-60, ISBN 953-6894-09-2, Croatia, June 2003, Zagreb
Pourbaix M. (1966). Atlas of Electrochemical Equilibrium in Aqueous Solutions, Pergamon Press, Oxford, London, Paris, Toronto, New York, Frankfurt
Traber, K. (1996). Fogra No 32., 107, Munchen