Most household scouring powders and pastes scratch or dull porcelain enamel surfaces, according to tests made in the household equipment department at Iowa State College. Dirt and stains adhere readily to enamels that have been roughened by abrasives, additional scouring is necessary, and a vicious cycle of staining and scrubbing begins.
"Do Cleaning Powders Scratch Porcelain Enamel?,"
Farm Science Reporter: Vol. 3
, Article 6.
Available at: http://lib.dr.iastate.edu/farmsciencereporter/vol3/iss2/6