A radiation curable ink composition comprising at least one initiator and at least one polyhedral oligomeric silsesquioxane (POSS) represented by the following empirical formula [R(SiO.sub.1.5)].sub.n wherein n=4, 6, 8, 10, 12, 14, 16 and larger and each R is independently hydrogen, an inorganic group, an alkyl group, an alkylene group, an aryl group, an arylene group, or non-heterocyclic group-containing organo-functional derivatives of alkyl, alkylene, aryl or arylene groups; and a process for obtaining a colourless, monochrome or multicolour ink jet image comprising the steps of jetting one or more streams of ink droplets having the above-mentioned composition onto an ink-jet ink receiver material, and subjecting the obtained image to radiation curing.