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Summary:
The lithographic process is based on the great difference that exists in wetting properties of various substances, but there are no methods to measure the relative wettability of these materials. The method of measuring wettability by contact angle measurements has been adapted to lithographic materials with good results. This method has been particularly valuable in studying steps in albumin and deep-etch type platemaking. Studies on mechanically cleaned plates show a fairly wide difference in wettability of various metals. Work on the changes in wetting characteristics of metal surfaces with changes of the chemical composition shows many changes that cannot be understood on the basis of present knowledge. Examples of these changes in wettability due to surface reactions are presented. A more basic knowledge of these reactions may be gained by the method of radio active tracers.