a polymerization apparatus includes a first chamber and a second chamber and a flexible , radioparent diaphragm separating the first chamber from the second chamber . a radiation source emitting polymerization - inducing radiation into the first chamber is provided . the second chamber is adapted for receiving a model and a foil , positioned between the diaphragm and the model , to be subjected to the radiation of the radiation source . a device for generating a pressure differential between the first and the second chamber for deflecting the diaphragm toward the model to thereby deform the foil at the model is provided . an adjusting device for adjusting the distance between the model and the diaphragm is provided .