Chemical graining: the lithographic plate surface is etched to produce a fine grain by the application of a strong acid or alkali solution.
化学磨版：用强酸或强碱溶液在平版印版的版面上腐蚀，造成幼细微粒表面。
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Mechanical graining: Mechanically roughening the surface of a metal sheet by means of abrasive powders, sand bursting, etc, for use as an offset plate.