It used to take about two years of air drying to season fir and spruce.

At present the artificial kiln performs this job in from twenty to forty days.

The kiln-dried lumber is just as strong and useful for construction as the air-cured stock.

Tests have proved that kiln drying of walnut for use in gun stocks or airplane propellers, in some cases reduced the waste of material from 60 to 2 per cent.

The kiln-dried material was ready for use in one-third the time it would have taken to season the material in the air.