Fig. 60
Timber may be considered to be sufficiently seasoned for rough work when it has lost one-fifth of its weight by evaporation.
Fig. 61
The poles from St. Petersburg have a narrow strip of bark removed in four equidistant longitudinal lines throughout their entire length. This treatment assists drying, and tends to prevent dry rot.
Weather shakes sometimes form on the outside of the wood while seasoning (see [fig. 61]).
They arise owing to the sapwood contracting more when drying than the heartwood. Unless they extend to a considerable depth they do not affect the quality of the wood. Balk timbers, where the sapwood is uncut, and whole timbers principally suffer in this manner.
Water seasoning—that is, having the timbers completely immersed in water for a short time before drying. This is a common practice. It is frequently carried out at the docks, where the balks may be seen floating about on the surface of the water. This is a bad method, as the wood is at the same time under the influence of water, sun and air.
Water seasoning may make the wood more suitable for some purposes, but Duhamel, while admitting its merits, says: ‘Where strength is required it ought not to be put in water.’
Description.—Pine or northern fir (Pinus sylvestris) is light and stiff, and is good for poles and scaffolding purposes, but only the commonest of the Swedish growths are used for this purpose. The hardest comes from the coldest districts. It has large red knots fairly regularly placed, inclined to be soft, and starting at acute angles. It grows chiefly in Northern Europe.