urethane derivatives acetophenone michler 39 s ketone benzophenone as well as its derivatives benzoyl benzalchloride and especially benzildimethyl ketal have proven to be especially suitable it is unexpected that in spite of the intensive hardening and crosslinking of the binder especially on the surface of the dye coating on the heat transfer the transfer of the sublimable dye is not affected during the later transfer printing i e during the sublimation of the dyes from the heat transfer onto the textile material moreover in spite of the relatively high concentration of sublimable dyes in such offset printing ink materials the uv initiators bring about a sufficient hardening of the oily hydrophobic printing material on the heat transfers during the irradiation which lasts only fractions of a second thus when polymerizable binders and uv activators are of a suitable composition radiation exposure times of 0 1 0 3 seconds can lead to the desired immediate hardening of the prints on the heat transfer backing so that the printer is then immediately ready to test the so obtained heat transfer to determine its transfer printing properties without the need to fear that the color images would change after storage since the hardening of the binder is not brought about through oxidizing time dependent procedures the dyes remain unchanged accordingly the heat transfers obtained in accordance with the invention can thus be stored practically indefinitely since the radiation crosslinking of the polymerizable vinyl group containing binders effected through the exposure to the uv light takes place in a fraction of a second the color layer printed in accordance with the offset.