In 1979, a number of glued laminated poles treated with CCA and creosote were placed in a greenhouse in Uppsala, in the Simlångsdalen test field in south-western Sweden and in a power lane in Vuollerim in northern Sweden, in order to study their resistance against biological degradation. The test poles were treated in a two-step process. All laminations of Scots pine (Pinus sylvestris) were first treated with a CCA-preservative, Boliden K33, followed by a second treatment with creosote or copper naphthenate stain applied after assembling the laminations, in the majority of cases after incising of the originally CCA-treated poles. Half the number of poles were equipped with a top cover of aluminium to protect the end grain The poles tested performed remarkably well after 43 years of exposure. The CCA+creosoted poles performed somewhat better than the CCA+CCA-treated and CCA+stained poles. Poles with aluminium top cover were less susceptible to decay in the upper-most part than poles without aluminium top cover. Although the decay was sometimes rated as 3 or 4, it occurred only in relatively small pockets and was not regarded as a hazard to the structural integrity of the poles. Delamination and cracks were not an issue either.

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