Dry heat process for dyeing and printing organic material which can be dyed with cationic dyes

In a dry heat transfer process for the dyeing, printing or optical brightening of organic material susceptible to dyeing with cationic dyes which comprises (1) bringing the surface of the said organic material to be dyed, printed or optically brightened into contact with the treated surface of an inert carrier, said surface being treated with a printing ink containing at least one finely divided, electroneutral, deprotenized cationic dye or fluorescent brightener of the formula ##STR26## wherein R is an aromatic, heterocyclic or aliphatic radical which contains a deprotonized nitrogen atom (.dbd.N--), each of X.sub.1 and X.sub.2 independently is N, CH or CR.sub.2, in which R.sub.2 is alkyl of 1 to 4 carbon atoms, aryl or aralkyl, Z is a divalent radical which optionally contains further heteroatoms or fused rings and which completes the nitrogen-containing ring to form an unsaturated 5- or 6-membered ring, and R.sub.1 is substituted or unsubstituted alkyl, and the deprotonized nitrogen atom in R is in conjugation to the ##STR27## group, irrespective of the length of the conjugation system which advantageously extends over 3 to 17 members, (2) subjecting the said organic material and inert carrier while in contact to a heat treatment of 120.degree. C. to 210.degree. C., and (3) separating the said organic material from the said inert carrier, the improvement according to which the printing ink employed to treat the surface of the inert carrier additionally contains an indicator dye which does not exhibit acid reaction.