Museum plywood -Specification
2007 Edition

The acceptable timber species for face veneers, core veneers, and cross bands in museum plywood must comply with Clause 3.1 of IS 710. Commonly approved species include Shisham (Dalbergia sissoo), Teak (Tectona grandis), Sal (Shorea robusta), Eucalyptus, and other durable hardwoods exhibiting suitable physical and mechanical characteristics. The use of alternative species requires prior consent from the purchaser and must possess equivalent properties. Preferably, a single timber species is used; however, if multiple species are combined, their compatibility must be ensured to prevent issues such as differential shrinkage and bonding failures. This ensures the plywood's durability, stability, and aesthetic suitability for museum furniture.

IS 15791 sets the maximum allowable formaldehyde emission at 0.5 milligrams per 100 grams of plywood, as stated in Clause 9.4. The formaldehyde content is measured using the desiccator method described in Annex B, which involves placing a plywood specimen in a sealed desiccator with distilled water for three days, followed by chemical analysis involving titration with iodine, sodium hydroxide, sulfuric acid, and sodium thiosulphate. The formaldehyde amount is calculated using the formula Formaldehyde (mg) = x × 0.15, where x is the volume of sodium thiosulphate solution used. Compliance with this limit ensures safety for indoor applications and is mandatory for BIS certification.

Under IS 15791, fire retardant treatment for plywood is mandated as per the guidelines provided in IS 5509. The treatment involves the impregnation or surface application of fire retardant chemicals that enhance the plywood's resistance to ignition and flame spread. The plywood must meet performance criteria such as flame spread limitation and charring resistance as detailed in IS 5509. Testing methods specified within IS 5509 assess parameters including ignition time, flame spread, and smoke generation to verify effectiveness. Thus, IS 15791 defers to IS 5509 for detailed chemical treatment procedures and fire performance evaluations.

The dimensional tolerances specified in IS 15791 Clause 7.3 for museum plywood panels are as follows: Length tolerance is +6 mm and -0 mm; width tolerance is +3 mm and -0 mm; thickness tolerance is ±10% for thicknesses less than 6 mm and ±5% for thicknesses 6 mm and above. Squareness and edge straightness tolerances are limited to 0.2% or 2 mm per 1000 mm length. Standard panel sizes include 2400 × 1200 mm, 2100 × 900 mm, 2100 × 1200 mm, 1500 × 900 mm, and 1800 × 1200 mm, with other sizes negotiable between manufacturer and purchaser. These stringent tolerances help maintain the structural integrity and fit essential for protecting valuable artifacts.

According to Clause 11 of IS 15791, every plywood product must be permanently and clearly marked with the manufacturer's name or trademark, the year of manufacture, the plywood thickness, and the type of fire retardant treatment applied, if any. The product may also carry the BIS Standard Mark, which is subject to licensing under the Bureau of Indian Standards Act, 1986. Manufacturers must obtain authorization from BIS to use this mark and comply with prescribed conditions. These marking requirements ensure traceability, quality assurance, and consumer confidence in the product.