Abstract: A process is provided for transfer printing into a substrate comprising applying onto a temporary transfer support in a desired pattern a heat transfer printing ink composition comprising a sublimatable dye, fine powder graphite and a strong acid in a carrier liquid, bringing the transfer support containing the ink into close contact with the substrate, the ink being in direct contact with the substrate, thereby temporarily transferring a portion of the ink to the substrate as a result of the direct contact, and permanently transferring the ink into the substrate by applying heat and, optionally, pressure. Suitable substrates into which the desired pattern may be transferred include paper, wood, plastic, natural cloth, synthetic cloth, carpet material, concrete, glass, metal such as steel, porcelain and ceramic.