Methods for field testing of preservatives in wood
1993 Edition

The standard specifies that test specimens for field evaluation should be heartwood pieces measuring 305 mm in length with a square cross-section of 38.1 mm by 38.1 mm, free from knots, stains, decay, or defects. For stake tests, specimens measuring 153 mm by 38 mm by 6.25 mm are prepared from well-seasoned planks of reference species such as Chir and Mango. Each species is sampled from six logs (two logs from each of three distinct regions), from which six specimens per preservative level are obtained. Testing includes three preservative absorption levels plus an untreated control to ensure consistent and reliable assessment of wood preservative performance under natural conditions.

Termite damage evaluation involves systematic visual inspections combined with damage quantification through a numerical rating system. Inspections are typically scheduled quarterly during the first year, biannually in the second year, and annually thereafter. Visual assessment is complemented by a knife test when the extent of decay is uncertain. The damage is rated based on the percentage of surface area affected, with categories ranging from no attack (0%) to very heavy attack (above 50%), each assigned a corresponding score. This approach allows for consistent and objective evaluation of preservative effectiveness against termite infestation.

The standard prescribes testing wood specimens at three distinct preservative absorption levels for each chemical used, maintaining an absorption tolerance of ±2.5% of the target value. Additionally, six absorption levels may be applied for more detailed investigations as referenced in IS 401:1982. Each species is sampled from six logs sourced from different regions, with specimens treated to these absorption levels, including untreated controls. This stratified approach facilitates comprehensive evaluation of preservative efficacy across a range of treatment intensities.

The standard identifies Chir (Pinus roxburghii), a coniferous species, and Mango (Mangifera indica), a broadleaved hardwood, as reference timbers for durability benchmarking. These species provide baseline data for comparing the performance of other timbers under similar environmental and biological exposure. Specimens from these reference species are prepared from heartwood, measuring 305 mm in length and 38.1 mm square in cross-section, and tested in both untreated and treated conditions at multiple preservative absorption levels.

Inspection intervals vary depending on the test phase and specimen type. For general specimens, monthly inspections are advised during the first year, followed by bi-monthly checks in the second year, and semi-annual assessments thereafter. When specifically evaluating preservative effectiveness against termites, inspections should be conducted quarterly in the first year, every six months in the second year, and annually in subsequent years. Inspections involve visual assessment of termite and fungal damage, supplemented with knife tests as necessary, ensuring continuous monitoring of wood condition and preservative performance.