NOVELTY - A printing or coating composition (C1) comprises a material to be deposited on a substrate and a non-volatile liquid vehicle for the material. The liquid vehicle is cleavable without decomposition of the material, cleavage of the vehicle producing decomposition products that are more volatile than the vehicle and which can be evaporated to dry the composition.    USE - As a printing or coating composition e.g. printing ink useful for applying a material to a substrate (claimed) and in polymer solar cells, organic field effect transistors, organic light emitting diodes, organic electro active materials.    ADVANTAGE - The thermally decomposable filler or viscosity modifier enables more viscous formulation that can be printed as a thicker wet layer without the finished dry layer being commensurately thick. The thermo-cleavable fillers or viscosity modifiers allow to raise viscosity and printing of a thicker wet layer, but by decomposing during the drying process, they do not contribute to the final dry layer thickness. This allows the printing of a thinner, defect free, dry layer. The non-volatile solvents/fillers are much easier to work with since the ink or other coating composition will not dry out during the application operation. A larger range of viscosities can be attained which allows for controlling film thickness and obtaining larger film thicknesses. The non-volatile solvents/fillers are odorless or low in odor and are much less toxic and irritating than volatile solvents, thus increasing safety and easy handling.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) applying a material to a substrate involving applying to the substrate the composition (C1), heating the composition to decompose the vehicle component of the composition and drying the composition; and    (2) a thermally decomposable solvent or filler of formula R2-O-C(=O)-(O)-C(R3)(R1)-CH3 or R-C(CH3)2-O-C(=O)-CH2-C(=O)-O-C(CH3)2R.    R2=organic substituent such that R2-OH is a volatile alcohol;    R1=aliphatic or aromatic substituent of more than three carbon atoms such that -C(=CH2)-R1 is volatile;    R3=1-3C alkyl;and    R=aliphatic or aromatic substituent of more than three carbon atoms such that -C(=CH2)R is volatile or is thermally itself decomposable to produce volatile products.