Incising as a possible technique to improve penetration and retention of creosote in the butt end of Eucalyptus saligna power transmission poles in Kenya was investigated. Debarked, butt-end samples from whole poles were seasoned (15% MC), incised using four patterns of incisions, sealed at the top or small diameter end, and pressure treated with a mixture of creosote-furnace oil (60/40 mix) at a commercial plant using a full cell process. They were then conditioned in the open for 3 months to allow evaporation, migration, and bleeding. The samples were subsequently leached in running tap water for 21 days, air-dried for 8 weeks under cover and retentions calculated on a weight-gain basis and compared. Discs were removed from the middle (450mm) of the samples, and radial penetration assessed visually and measured. Compared to un-incised samples, both penetration and retention were substantially improved in samples with closer incisions of 20 mm x 20 mm, by 58.6% or 89.8 mm and 87.0% or 146.4 Kg/m3 respectively. Wider incisions 0f 40 mm x 40 mm achieved lower improvements, 17.3% or 66.4 mm for penetration and 19.8% or 93.8 Kg/M3 for retention. The 4 incising patterns achieved consistently higher penetration and retention of creosote compared to un-incised control samples, which achieved lower average penetrations (56.6mm) and retentions (78.3Kg/M3). Butt-end, or incising the ground-contact sections of transmission poles may be a feasible technique for improving both penetration and retention in the more vulnerable portions of poles, and thus substantially increase service lives of eucalyptus poles in the country. Further investigations are necessary to establish patterns of incision and appropriate treatment schedules.

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