Abstract: A method of preventing clogging of nozzles, particularly nozzle orifices in a drop-on-demand ink jet printers, during intervals when no ink flows through the nozzles, e.g. during non-printing intervals, when using an ink composition intended for recording permanent information on essentially non-absorbent surfaces. The ink composition is made up of a solvent, a non- or low-volatile fraction and a colorant. The relative quantities and solubility of the constituents are selected such that when printing terminates and a portion of the solvent evaporates at the nozzle orifice, a concentration of colorant and less volatile fraction builds up in the region of the nozzle orifice. This causes the colorant to migrate to an environment in which its affinity is greater, i.e. further within the nozzle.

Abstract: Methods of coating piezoelectric substrates with substantially uniform layers of a semi-conducting material are disclosed including placing the substrate in a heated deposition chamber at reduced pressure and depositing a layer of semiconducting material on the substrate by thermally activated chemical vapor deposition, including admitting a gas bearing the semi-conducting material into the chamber at a pressure of between about 13 and 200 Pa and a temperature of between about 300.degree. and 700.degree.C. so that a layer of semi-conducting material having a desired smoothness is obtained.