Open-pored originals made of dry and cracked clay, stone, concrete, extremely dry wood with cracks and fissures; such as old wood reliefs, models and figures must be pre-treated before casting in such a manner as to prevent the mould casting material from settling and damaging the models afterward when they are removed. Pre-treat stone and ceramic models with casting paste paint primer in order to stabilize the surface. Paint wooden objects twice with a matt solvent-containing transparent varnish in order to seal the surface. The paint on transparent mould Separating Soap. Melt the soap like wax in a water bath on your stove and then apply it with a soft brush. After it hardens, the soap builds a thin separating layer to the mould casting paste. Remove soap residues with hot water when the negative mould is finished. The pre-treatment cannot be seen on the dried original.