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The merits of zinc and aluminium have been debated since their introduction to lithography. Each metal has had strong advocates, and excellent work has been produced over the years using both materials. From the practical viewpoint, there is little difference between the two metals in cost, outlay of processing materials, and easy of printing. It is safe to say that each type of plate, when handled knowledgeably will perform equally well. The choice of wether to stock one or both types of plates and suitable processing materials for each is largely dependant on the subjectives of the lithography shop. It might be advisable for school shops to stock only one metal in order to minimize cost and to avoid confusion and contamination of the processing materials necessary for both types of plates. The following chart comparing the merits of the two metals will serve as a basic guide:
Zinc Aluminium Darker surface colour, somewhat detrimental for close-valued tonal drawing. Crayon and wash drawings appear markedly different from those on stone Lighter surface colour, easier to see the drawing of close tonal work. Crayon and wash drawing appear more nearly like those on stone. "Peau de crapaud" wash techniques possible "Peau de crapaud" wash techniques not possible Inherently sensitive to grease. Inherently less sensitive to grease Inherently less sensitive to water Inherently very sensitive to water Produces strong image areas Produces moderately strong image areas Produces less firm non-image areas Produces excellent non-image areas Easy to stabilize added work after counteretching Somewhat difficult to stabilize added work after counteretching Prone to scumming when printing, unless effectively desentitized Resistant to scumming when printing Moderately difficult to stabilize deleted work after processing Moderately easy to stabilize deleted work after processing Oxide films jeopardize effective desensitization Oxide films jeopardize effective desensitization
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