Closed cell foam
A dense, durable foam. Closed cell foams have unconnected air cells that are formed by incorporating gas bubbles into the structure of the foam. This can be done mechanically by mixing in the bubbles or a low-boiling solvent into the polymer prior to curing, or chemically by adding a blowing agent that evolves gas.
- Pam Hatchfield, Pollutants in the Museum Environment, Archetype Press, London, 2002