Apparently, layer-building care products have left residues on the surfaces which are being redistributed with each wiping. Dilute Lithofin KF Intensive Cleaner approx. 1:5 with water and apply it to the surface. Allow the product to work for 20 minutes, then brush and thoroughly rinse the surface with plenty of clear water. For regular maintenance, use Lithofin KF Conditioning Cleaner (for Australia and New Zealand: Lithofin KF Vitra-Clean).