The standard outlines laboratory testing procedures to establish the minimum effective retention levels of wood preservatives against fungal decay, employing soil block and Kolle flask methods. It specifically addresses treatment and testing of chir and mango sapwood to evaluate preservative performance under controlled conditions. This document is vital for scientists, manufacturers, and quality assurance personnel involved in wood preservation research and product validation.
Overview
The standard outlines laboratory testing procedures to establish the minimum effective retention levels of wood preservatives against fungal decay, employing soil block and Kolle flask methods. It specifically addresses treatment and testing of chir and mango sapwood to evaluate preservative performance under controlled conditions. This document is vital for scientists, manufacturers, and quality assurance personnel involved in wood preservation research and product validation.
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The standard specifies the use of sapwood from Chir (Pinus roxburghii) and Mango (Mangifera indica) for test specimens. The blocks must be free from defects such as knots, mould, and discoloration. Dimensions vary depending on the clause, for instance, 50 mm × 25 mm × 15 mm along the grain or 19 mm cubes with a central hole for specific tests. Prior to testing, blocks are oven-dried at 100–105°C to achieve constant weight, ensuring uniformity and reliability in preservative assessments.
Threshold retention represents the minimum preservative concentration (kg/m³) that effectively prevents wood decay, limiting weight loss to 5% or less. The process involves impregnating wood blocks with various preservative levels, conditioning them, and then exposing the samples to wood-degrading fungi. Weight loss is measured after fungal exposure, and the lowest preservative retention level associated with weight loss not exceeding 5% is identified as the threshold retention, ensuring optimal protection.
The standard advises using fungi that demonstrate resistance to preservatives, rapid growth, and significant wood degradation capacity. Specifically, tolerant fungi such as Lentinus lepideus (resistant to creosote and creosote mixtures) and Poria monticola (tolerant to copper and zinc compounds) are mandated for inclusion in all preservative efficacy tests. These fungi provide a stringent challenge to preservatives, ensuring that test results accurately reflect protective performance under adverse fungal attack.
Test blocks are incubated under controlled conditions of 25 ± 1°C temperature and 70 ± 4% relative humidity for a period of 12 weeks. During incubation, blocks are placed aseptically on glass rod supports within culture flasks, ensuring contact with aerial mycelium only, to prevent preservative leaching. After incubation, blocks are carefully cleaned of fungal growth, weighed if moisture content determination is required, then dried and conditioned at 30°C and 70 ± 4% relative humidity until constant weight is achieved.
Preservative retention (R) is calculated using the formula R = (G × C × 100) / V, where G is the mass of preservative solution absorbed by the wood block (difference between mass immediately after treatment and initial dry mass), C is the concentration of preservative in the treating solution expressed in grams per 100 grams of solution, and V is the volume of the wood block in cubic centimeters. The retention value is typically expressed in grams per cubic centimeter and can be converted to kilograms per cubic meter by multiplying by 1000. This calculation quantifies the amount of preservative effectively impregnated into the wood.
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