The influence of water on the rheological properties has been investigated for boric oxide glass and two sodium borate glasses. The reducing influence of water on the viscosity appears to be about five times stronger than the increasing influence of sodium oxide. The deviations from Newtonian flow (Bingham yield values) have shown a similar picture. The explanation of the behaviour of water is based on the idea that B=O=B bonds in the glass are "hydrolysed", which causes a preferable viscous flow along OH groups.
Visser, T. J. M., & Stevels, J. M. (1972). Influence of water on the rheological properties of alkali borate glasses. Journal of Non-Crystalline Solids, 7(4), 401-409. https://doi.org/10.1016/0022-3093(72)90274-8