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Marking material, , Objectives: At the end of this lesson you shall be able to, * name the common types of marking material, , * select the correct marking material for different applications., , Common types of Marking Materials, , The common marking materials are Whitewash, Cellulose, Lacquer, Prussian Blue and Copper Sulphate., Whitewash, , Whitewash is prepared in many ways., , Chalk powder mixed with water, , Chalk mixed with methylated spirit, , White lead powder mixed with turpentine, , Whitewash is applied to rough forgings and castings with, oxidised surfaces. (Fig 1), , , , Fig 1, , , , , , , , [uowra0rs1, , , , Whitewash is not recommended for workpieces of high, accuracy., , Cellulose Lacquer, , This is a commercially available marking medium. It is, made in different colours, and dries very quickly., Prussian Blue, , This is used on filed or machine-finished surfaces. This, , will give very clear lines but takes more time for drying, than the other marking media. (Fig 2), , , , Fig2, , , , , , , , Copper Sulphate, , The solution is prepared by mixing copper sulphate in, water and a few drops of nitric acid. The copper sulphate, is used on filed or machine-finished surfaces. Copper, sulphate sticks to the finished surfaces well., , Copper sulphate needs to be handled carefully as it is, poisonous. Copper sulphate coating should be dried well, before commencing marking as, otherwise, the solution, may stick on the instruments used for marking., , The selection of marking medium for a particular job, depends on the surface finish and the accuracy of the, workpiece.