Polychrome sculpture, which constitutes much of our heritage in statuary and architecture, presents special conservation problems. Treatments which form inorganic salts within the stone may obscure such traces, and application of resins often darkens the stone. New treatments involving alkyl silicates and silicone resins have gained acceptance. Of these, the alkyl trialkoxy silanes have good results regarding the consolidation of porous stone and are said to leave the surface undarkened. An investigation followed by tests and subsequent silane treatment of an Egyptian polychrome and gilt sandstone triad from the first century BC shows that this method still presents problems for polychromy. These problems are set out and discussed.