Eraser powder

Draftsman's eraser powders (e.g. Skum-X or Opaline) can be used to remove ingrained dirt from relatively sound surfaces but are not safe for surfaces that have cracks or unevenness where the powder could get left behind. Various kinds of rubber powder are available, but the natural rubber ones are probably best. Rub the powder into the surface with the fingertips until cleaning is seen to be effective. When finished, use a brush to sweep all the crumbs into a vacuum cleaner nozzle covered with cheesecloth. Be careful to avoid patchy cleaning or overcleaning.

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