The surface must be sound and thoroughly cleaned before applying Vetoseal XX777. Remove all loose particles, old mortar, laitance, dirt, paint, etc., by brushing with a stiff/wire brush or other suitable means. Scour away fungi or Algae using hypochlorite type bleach or proprietary fungicidal solution and then wash with water. Remove all traces of oil and grease with an industrial-grade chemical degreaser or another suitable degreasing agent.