entirely degraded at ambient temperature within about 8 h the result of the above described process is the production of a self supporting photoresist membrane which is liberated from the silicon substrate by the degradation of the intermediate biopolymeric for example gelatin based in the present example layer in a third embodiment a bath according to the invention will be described an action of which provides a degradation stop in analogy to known etching stop layers when a selected layer is to be advantageously protected against external influences and at the same time reliably set free from a substrate on which it is initially formed for example when producing thin structurized membranes which are described by way of example using gelatin such gelatin layer which later forms the membrane is doped by metals or specific inhibitors for degradation of the enzyme employed such inhibitors are generally artificial analogues of the transition states of the substrate which has to be enzymatically decomposed and have bonds which are not decomposable by the enzyme for example such inhibitors would have ether bonds which are not decomposable by proteases which decompose peptide bonds a first thin layer prepared in this manner to include such metals or specific inhibitors is provided with a second thin layer of agarose having a thickness of about 1.