Carborundum Grit

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forcat.jpgLithographers use carborundum, a uniform particulate abrasive material derived from black silicon carbide, to grain limestone for the lithographic process.

This domestic grade abrasive material is very uniform in particle size ranging from coarsest 80 grit to finest 320 grit.

Graining litho stones removes the previous image, this requires an abrasive material such as carborundum grit and a levigator to clean and polish the stone, creating a grease sensitive surface.

Carborundum grit is used in place of quartz and sand abrasives for graining lithographic stones. The graining procedure should be begun with coarser grades of carborundum grit. The sludge created when graining litho stones should be removed and replaced with new grit when it becomes sticky and dry. To remove the prior lithographic image completely from the litho stone, use a coarse grit until the dark areas of the image become light. Rinse the litho stone, levigator and your hands to remove all particles of abrasives before proceeding to finer grits. To finish the stone use finer grades of carborundum grit until the tooth or grain and finish of the stone's surface are ideal.

It is extremely important that the litho stone is completely flat and of a consistent thickness. The use of a precision straight edge and precision calipers during the graining procedure ensures that the stone is flat and level. Litho stones should be checked for a wedge shape, any wedge shaped stones should be corrected during the graining procedure.