The invention relates to a method for producing a synthetic body from a synthetic material obtained by radical polymerization, which is coated on one or several sides with an Si-containing or inorganic substance. According to the inventive method, a substrate is coated with a lacquer composition which contains inorganic particles dissolved in a solvent which may optionally also contain a flow-control agent. One or more substrates that are coated in this manner can be used to construct a polymerization chamber, the coated sides facing the interior of the chamber. After radical polymerization of a monomer mixture in the presence of a polymerization initiator and a separating agent mixture the inward inorganic coating is transferred from the substrate to or onto the surfaces of the radically polymerized synthetic material or the corresponding synthetic body. The invention also relates to the corresponding synthetic bodies and their uses and to the use of the separating agent mixture in the polymerization casting method.