THE EVALUATION OF THE QUALITY OF CORK PLANKS BY IMAGE-ANALYSIS

The quality evaluation of cork planks in relation to porosity may use image analysis techniques. Results are presented on the number, dimens ions, form and orientation of the lenticular channels in tangential, t ransverse and radial sections of cork planks of different thickness an d qualities. The porosity coefficient (% pore area in relation to tota l area) varied between 1.1%-18.9% and 2.1%-16.4%, respectively in tang ential and transverse/radial sections and is determined mostly by the number of pores larger than 0.8 mm(2) and by their average area. The p orosity may be used to define cork quality classes. Due to the heterog eneous porosity distribution in cork planks, an assessment of quality made on small cork samples will give a result with a large error For a n error below 15%, the observation in the tangential section should be made on a sample with a minimum area of 225 cm(2) (e.g. 15 cm x 15 cm ) and in the transverse and radial sections on a sample with a minimum length of 15 cm.