sugar soap

From the resemblance of the dry powder form to table sugar.

sugar soap (usually uncountable, plural sugar soaps)

1. An extremely powerful detergent used for washing surfaces prior to painting.
   • 1918, The American Perfumer and Essential Oil Review:

     A detailed discussion of the work of J. Boes and H. Weyland on the value of sugar soap was made by F. G. as had been already pointed out in last year's report.

   • 1930, The Chemical Trade Journal and Chemical Engineer:

     Sugar soap, states a writer in the "Pharmaceutical Journal," is a soap powder used by painters for washing down purposes before applying new coats of paint and varnish. It owes its name to its resemblance to Demerara sugar crystals, and is retailed in 1 lb. cartons at sixpence or less, and some of it is packed loose in casks.

   • 2002, Vinny Lee, The Essential Guide to Decorating:

     Previously painted surfaces should be wiped down with sugar soap solution to remove dirt and grease, and any rough patches or holes should be filled and sanded.