Abstract: The present invention provides a heat-sensitive recording material, characterized in that a carrier material carries at least one coating layer in which at least two colour-forming reactants A and B are contained, wherein the layer contains a water-insoluble or sparingly water-soluble iron compound as colour-forming reactant A and a water-insoluble or sparingly water-soluble phenol compound having 2 or more adjacent OH groups as reactant B separated from each other, wherein at least one of the compounds melts at less than 100° C. and this melt reacts with the other colour-forming reactant by colour development in less than 1 second's contact time and at least one of the two colour-forming reactants is present as particles having a size of less than 20 ?m.

Abstract: The invention relates to a reactive ink-jet printing method for implementation on substrates such as paper, board, corrugated cardboard, films, injection or compression moulded plastics parts, metal, ceramic surfaces, paint coats or corrosion protection layers, characterized in that the substrates are coated with a polyphenol, and a reactive ink composed of at least one dissolved metal salt selected from the group consisting of the compounds of iron, molybdenum, tungsten and titanium is reacted by ink-jet printing on or in the surface of the stated substrates, to form a stable colour complex which is immediately perceptible to the human eye, and the invention also relates to suitable coated materials and to a writing system for the implementation of the method.