museum boards 100% Cotton
They are composed of multiple layers of laminated paper commonly bonded using an ethylene vinyl acetate adhesive.
The carton is made of pulp composed of 100% cotton fibres or rags, with at least 95% alpha cellulose (B0127). Museum boards must contain less than 0.0008% reducible sulphur and an iron and copper content not exceeding 150 ppm and 6 ppm, respectively. The alkaline reserve must be between 2 and 5% of the total volume of the weight of the carton. Calcium, magnesium, and zinc carbonate are acceptable alkaline reserves. Museum boards may be coated with a non-ionic starch. All adhesives used in the manufacture of museum boards must have a pH between 7.0 and 9.5.
Museum boards, which are often described as being acid- and lignin-free, and occasionally fungicide or optical brightener additive free, are known for their high degree of purity, their resistance to delamination, and their ease of use. Since they are made from cotton fibres or rags, they are superior in quality to other types of conservation boards, which are made from chemical pulp. The cotton content makes museum boards very resilient and flexible, allowing them to return to their original shape after being distorted. They absorb shocks well and are more resistant to pressure than most other carton substrates. They are normally tinted throughout instead of just at the surface, and their colours, tints, or pigments, in addition to being resistant to degradation caused by light and abrasion, do not bleed.