Tredgold calls timber seasoned when it has lost 1/5 of its weight, and says that it is then fit for carpenters' work and common purposes. He calls it dry, fit for joiners' work and framing, when it has lost 1/3 of its weight.
The exact loss of weight must depend, however, upon the nature of the timber and its state before seasoning.
Timber should be well seasoned before being cut into scantlings. The scantlings should then be further seasoned, and after conversion the wood should be left as long as possible to complete the process of seasoning before being painted or varnished.
Mr. Britton states that logs season better and more quickly if a hole is bored through their centre. This also prevents splitting.
There are several different methods of seasoning timber, the principal of which will now be briefly described.
Natural Seasoning is carried out by stacking the timber in such a way that the air can circulate freely round each piece, at the same time protecting it by a roof from the sun, rain, draughts, and high winds, and keeping it clear of the ground by bearers.
The great object is to ensure regular drying. Irregular drying causes the timber to split.
Timber should be stacked in a yard, paved if possible, or covered with ashes, and free from vegetation.
The bearers used should be damp-proof, and should keep the timber at least 12 inches off the ground. They should be laid perfectly level and out of winding, otherwise the timber will get a permanent twist.
If possible, the timber should be turned frequently so as to ensure equal drying all round the balks.
When a permanent shed is not available, temporary roofs should be made over the timber stacks.
Logs are stacked with the butts outwards, the inner ends being slightly raised so that the logs may be easily got out. Packing pieces are inserted between the tiers of logs, so that by removing them any particular log may be withdrawn.
Some authorities have stated that timber seasons better when stacked on end. This, however, seems doubtful, and the plan is practically difficult to carry out.
Boards may be stacked in the same way, laid flat and separated from one another by pieces of dry wood an inch or so in thickness and 3 or 4 inches wide. Any that are inclined to warp should be weighted or fixed down to prevent them from twisting.
Boards are, however, frequently stacked vertically, or inclined at a high angle.
Tredgold gives some algebraic formulae for calculation of the time required, and a table deduced therefrom.
Mr. Laslett has, however, compiled a table from practical observation.
He says : "My experience of the approximate time required for seasoning timber under cover and protected from wind and weather is as follows : -
Pieces 24 inches and upward square require about .
,, Under 24 inches to 20 „......
„ 20 „ 16...........
„ 16 „ 12.........
,, 12 ,, 8 ,, •
8 ,, 4 .........
"Planks from 1/2 to 2/3 the above time according to the thickness."
Mr. Laslett further states that if the timber is kept longer than the periods above named, the fine shakes which show upon the surface in seasoning " will open deeper and wider until they possibly render the logs unfit for conversion."
Tredgold says that the time required under cover is only 5/7 of that required in the open.
Water Seasoning consists in totally immersing the timber, chaining it down under water, as soon as it is cut, for about a fortnight, by which a great part of the sap is washed out. It must then be carefully dried, with free access of air, and turned daily.
Timber thus seasoned is less liable to warp and crack, but is rendered brittle and unfit for purposes where strength and elasticity are required.
Care must be taken that the timber is entirely submerged. Partial immersion, such as is usual in timber ponds, injures the log along the water line.
Timber that has been saturated should be thoroughly dried before use when taken from a pond, cut up and used wet, dry rot soon sets in.