The invention relates to flexible foams having a flexible abrasive surface and containing 1 to 90 wt.%, relative to the uncoated substrate, of a mixture containing the condensation product of 99.985 to 20 wt.% of at least one pre-condensate of a heat-curing resin, 0 to 10 wt.% polymer thickener chosen from the group consisting of biopolymers, associative thickeners and/or fully synthetic thickeners, 0.01 to 10 wt.% curing agent, 0 to 10 wt.% surface-active substances or surfactants, 0 to 15 wt.% dyes, pigments or mixtures thereof, and 0 to 75% water, said mixture containing 10 to 70 wt.% of one or more binders, relative to the above mixture, from the group comprising polyacrylates, polymethacrylates, polyacrylonitriles, copolymers of acrylic acid esters and acrylonitrile, styrene and acrylonitrile, acrylic acid ester and styrene and acrylonitrile, acrylonitrile and butadiene and styrene, polyurethanes, melamine formaldehyde resins, phenol formaldehyde resins, urea formaldehyde resins, melamine urea formaldehyde resins, melamine urea phenol formaldehyde resins, and urea glyoxal resins.