In this investigation, formulations of PP523 and TCMTB were sprayed on softwood lumber using a specially-constructed “Electrodyn” sprayer developed by Imperial Chemical Industries PLC. The lumber surfaces were evaluated subsequently for overgrowth by fungi after a four-month period of incubation. Formulation PP523 provided adequate protection of hem-fir lumber while TCMTB gave suitable protection to the SPF lumber. Drop size and spray distribution patterns on the wood, were affected by Electrodyn nozzle voltage, fluid flow rates, height of the nozzle above the lumber surface and speed of lumber passing the nozzle. The wrap-around effect, caused by the charged drops, gave reasonable coverage by the chemical on the sides and lower surfaces of the lumber.
The efficiency of chemical application could be at least doubled when compared with conventional hydraulic sprays. Volumes of solution used to obtain adequate control of mould and stain on lumber were several magnitudes less than with hydraulic sprays while surface concentrations of chemical required to achieve protection were possibly lower. This technology could significantly advance the current procedures used in sawmills throughout Canada, by providing a more efficient and much safer method for applying antisapstain chemicals on lumber.