Grey Patch is a polymer-modified, calcium-aluminate, rapid-setting, interior patching compound used to fill voids and smooth the surfaces of open concrete and approved wood underlayments and may be used without a primer or additive. Common floor coverings such as VCT and carpet can be installed in as little as 1 hour. When used in the “skim-bond system,” Grey Patch can be used on properly prepared burnished concrete, cutback and non-water-soluble adhesive residue, cement terrazzo, ceramic and quarry tile; single-layer, fully-bonded VCT; and embossed non-cushioned, residential sheet vinyl, or other non-porous surfaces.