propulsion gas or propellant gas to the liquid to be sprayed can result in the u201c cooking u201d or u201c baking u201d of the liquid by boiling off of the liquid solvent premature agglomeration aggregation or chemical reactions all of which separately or in combination tend to induce clogging by reaching a critical temperature in the liquid preventing this type of heat induced clogging is achieved by minimizing heat transfer between the unheated liquid to be sprayed and the heated propulsion gas until just outside their respective spray orifices thereby maintaining the unheated liquid below its critical temperature special heat transfer minimization methods are used in the nozzle to limit heat transfer from the heated propulsion gas to the liquid flow prior to liquid efflux in one embodiment of the nozzle the high velocity of the heated gas efflux creates a venturi generated low pressure region which is in turn used to draw ambient non heated air over a tube containing the liquid to be sprayed thus minimizing heat transfer from the heated propulsion gas to the sealant the pressure of the low pressure region may be obtained by the well known bernoulli equation widely used in hydraulics and fluid mechanics the result is greatly reduced clogging of the spray nozzle other embodiments employ thermal insulation techniques in various configurations to minimize heat transfer it has been found that the.