A series of preservative treatments with creosote using Lowry and Rueping schedules was undertaken. From these treatments the most suitable impregnation conditions for water stored Sitka spruce (Picea sitchensis) and Norway spruce (Picea abies) transmission poles were determined. Preservative distribution and permeability values for poles of both species were used to decide the optimum season and duration of water storage. A testing programme on full size poles was carried out to determine the strength properties of home grown Sitka spruce poles, and to evaluate the effect of water storage on their strength. Extensive testing of small clear specimens of both water stored and control material was also undertaken. Home grown Douglas fir and European larch and imported Scots pine poles were tested to provide comparative pole strength data. A bibliography on methods of increasing the permeability of refractory wood species has been compiled by Unligil (1969). Other reviews relating to this topic have been prepared by Jutte (1971), Greaves (1971) and Rossell, Abbot and Levy (1973). Recently Unligil (1972) has shown that water storage of white spruce (Picea glauca) for five to nine weeks is sufficient to ensure full sapwood penetration with creosote in air-dried bolts using an eight hour Lowry process.

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