A method of protecting a biologically active substance against denaturation, wherein a liquid (14) containing the active substance and a matrix-forming substance are deposited on a target surface (18) and dried so as to form a solid amorphous matrix (26) with the molecules of the active substance embedded therein, wherein an ink jet printer (10) is used for depositing the liquid (14) on the target surface (16) in the form of droplets (12) having a volume small enough to cause the liquid to dry when it impinges on the target surface (16) and to be held on the target surface through adhesion.
