Mechanism of infection of fir wood joinery; Part 2: Sequence and intensity of attack of microorganisms

In Croatia the primary raw material for joinery production is silverfir wood (Abies alba Mill). L-joints made of home-grown fir sapwood and prepared according to EN 330: 1993. were used to establish the colonisation and infection of microorganisms to compare the performance of untreated and 1% TnBTO treated L-joints by ten-minute immersion. The L-joints surfaces were coated with two types of liquid coat, and exposed on three different climate sites in Croatia. The first type of coat was alkyd paint and the second was a stain, in three different colours: white, brown and black. The untreated L-joints were examined after 1, 2, 3, 4, 6, and 12 months and treated after 12 months of exposure. The influence of the climate, and the type of coat were the most important factors which affected the rate of colonisation. In Zalesine, a mountain site with the highest average air humidity and the greatest amount of precipitation, colonisation was fastest and strongest. The lowest bacterial and fungal colonisation occurred in L-joints exposed in Rovinj, a site on the Adriatic coast, particularly on those L-joints coated with a darker stain. It was due to the well known vaporous diffusivity of the stains and the fact that Rovinj had the largest number of sunny days during the first two months of exposure when the dark stain surfaces absorbed many more of the sun's heat rays which caused accelerated seasoning, lower moisture contents and lower bacterial colonisation. The influence of coat colours later was not significant. The differences between one year exposed untreated and treated L-joints were significant according to the moisture content, permeability and fungal colonisation. The colonisation and fungal attack of treated L-joints was lower, particularly of those coated with stain. The most frequently isolated fungi were Alternaria alternata (Fr.) Keissler, Gloeophyllum trabeum (Fr.) Pers. and Aurobasidium pullulans (de Bary) Arnaud.