During assessment of the ground contact stakes in the Norwegian test field, we have frequently found that the first visual rot attack is in the zone of the stakes, where the stakes have been in contact with each other during the fixation. These parts are usually light green, caused by the lack of light during fixation, compared to the rest of the stake surface, which has a darker colour. To investigate if light on the stakes during fixation can affect the durability of the treated wood, we started a test in 1993. CCA and ACQ treated stakes were tested according to EN 252. The stakes were treated with two retentions of each salt. One according to the Nordic Class A (for ground contact i.e. hazard class 4) and one lower retention (25 % of the class A retention. This is even lower than the Nordic class AB (HC 3) retention). Before exposure they were fixed in 7 different climates: 1) Normal fixation = 60 % RH and 25 °C, light days, dark nights for 7 days, 2) Dark fixation = normal fixation without light for 7 days, 3) UV-light fixation = normal fixation with UV-light 24 hours for 7 days, 4) Hot fixation = 95 % RH and 90 °C for 2 hours, 5) Cold fixation = 50 % RH and 10 °C for 30 days, 6) Dry fixation = 10 % RH and 50 °C, for 24 hours, 7) Wrapped fixation = each stake packed in black plastic foil, 50 °C and without light for 24 hours. The colour of the ACQ stakes varied from light green to black, depending on the fixation climates. These different colours and the durability results after 5 years were reported at the 30th IRG meeting in 1999. The different fixation procedures give only small differences in durability/rot index after 9 years in field test. Hot, dry and wrapped fixations give ACQ a better durability than CCA in the Nordic class A retention. None of the ACQ stakes were rejected in the first 9 years, while the CCA stakes had a few rejected stakes after 8 and 9 years caused by sot-rot. For the low retention, ACQ gives a better durability than CCA for all fixation procedure, but both preservatives had several rejected stakes.

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