It is most important to keep the work area free of the erasing granules produced by cleaning. If granules remain on the working surface and the artifact to be cleaned is placed over them and rubbed, holes may be created in the artifact. Working on large sheets of brown kraft paper may help you to dispose of the granules. While granules will remove most surface dirt, block erasers may remove even more. It is not necessary, or even desirable, to remove all surface dirt from old papers.
Erasers can abrade soft papers and are best used by persons experienced in surface cleaning.
If it is necessary to use an abrasive harsher than granules, a block eraser is comparatively safe. Proceed with caution, trying an inconspicuous spot first. Rub gently in a single direction or in small circles. Take care not to create light erased areas, which will contrast with the general surface color. Do not rub erasers over pencil, color, or inks.