Q. Ive read about artists who sometimes use a bleach/water solution to spray onto watercolor paintings to remove color. Is this archivally safe? Would it cause your paper to eventually yellow in the areas where its been sprayed? If this is a safe practice, whats the highest ratio of bleach to water that one could use?
A. Bleach is an oxidizing agent thats very effective at removing color—nonetheless, it should be avoided in works of art. In bleaching the paint, it may also bleach the paper in the area, causing an immediate problem of uneven tone in the color of the paper. It also oxidizes the cellulose in the paper, which will later cause it to turn yellow and deteriorate. This is one shortcut you should definitely skip.
Mark Gottsegen is an associate professor of art at the University of North Carolina at Greensboro and chair of ASTM Internationals subcommittee on artists materials.