Water uptake by some chamber materials.

The characteristics of water uptake by several materials have been studied. Nitrile rubber, silicone rubber and perspex retained substantial quantities of water. Metals took up smaller, but still significant, amounts of water, and glass was the least water-retentive material used in the tests. The surface structure of the material, revealed by scanning electron microscopy, does not necessarily account for its water uptake characteristics. The results are discussed in relation to the design and construction of psychrometer and porometer chambers.