Frequently Asked Questions about Steam Drying:

How does it work?
During the warming-up phase all air initially present in the kiln will be replaced by steam. The relative humidity of the air is during the warming-up phase kept at a maximum level close to 100 %, air vents are closed, but venting will occur based on the overpressure in the kiln resulting from the
increase of temperature and the supply of steam. After the temperature of the drying medium has approached 100 °C the climate has changed into saturated steam. If the saturated steam is further heated, by the heaters in the kiln, the steam will become super heated and the free water inside
the boards will start to boil. The temperature of the boards will stay at the boiling point of water, 100 °C, as long as the MC is above fibre saturation point. This boiling effect will cause a slight overpressure in the wood, comparable with the overpressure in a pan with boiling water causing a rattling lid. This internal overpressure speeds up the moisture transport from the core to the surface and consequently increases the drying rate.