A QUANTITATIVE WEATHERING STUDY OF WOOD SURFACES MODIFIED BY CHROMIUM-VI AND IRON-III COMPOUNDS .2. IMAGE-ANALYSIS OF CELL-WALL PIT MICRO-CHECKING

Radial longitudinal radiata pine wood surfaces were treated with dilut e aqueous solutions of chromium trioxide, ferric chloride and ferric n itrate. Treated and untreated specimens were then exposed to natural w eathering for 35 days. Scanning electron microscopy was used to obtain images of bordered and half bordered pits at treated and untreated su rfaces before and after weathering. Images were converted to a digital form and the micro-checking and enlargement of pit apertures during w eathering was then examined using image analysis. Application of chrom ium trioxide reduced the micro-checking and enlargement of both border ed and half bordered pit apertures during natural weathering. Both fer ric treatments increased surface degradation. Image analysis of the mi cro-checking and enlargement of pit apertures at treated wood surfaces during natural weathering shows potential as a quantitative method of assessing the protective effect of chemical treatments, but measureme nt of the checking and enlargement of half bordered rather than border ed pit apertures may be preferable since checking of the former is mor e uniform.