HAVING briefly alluded to the mischiefs consequent upon the use of woods in an improper condition, I shall proceed to describe the general modes pursued for avoiding such mischiefs by a proper course of preparation.
The woods immediately after being felled, are sometimes immersed in running water for a few days, weeks, or months, at other times they are boiled or steamed; this appears to be done under the expectation of diluting and washing out the sap, after which it is said the drying is more rapidly and better accom-plished and also that the colours of the white woods arc improved, (see article Holly in Catalogue, also Ebony,) but the ordinary course is simply to expose the logs to the air, the effect of which is assisted by the preparation of the wood into smaller pieces, approaching to the sizes and forms in which they will be ultimately used, such as square logs and beams, planks or boards of various thicknesses, short lengths or quarterings, etc.
The stems and branches of the woods of our own country, such as alder, birch, and beech, that are used by the turner, frequently require no reduction in diameter; but when they are beyond the size of the work, they are split into quarterings and stacked in heaps to dry, which latter proceeding should never be forgotten under any circumstances.
We know but little of the early treatment of the foreign woods used for cabinet-work and turning; some few of them, as mahogany and satin-wood, are imported in square logs; others, as rosewood, ebony, or coromandel, are sometimes shipped in the halves of trees, or in thick planks; but the generality of those used for turning are small, and do not require this reduction; these only reach us in billets, sometimes with the rind or bark upon them, and sometimes cleaned or trimmed.
The smaller hard woods are very much more wasteful than the timber woods; in many of the former, independently of their thick bark, the section is very far from circular, as they are often exceedingly irregular, indented, and ill-defined; others are almost constantly unsound in their growth, and either present central hollows and cavities, or cracks and radial divisions, which separate the stem into three or four irregular pieces.
Probably none of the hard woods are so defective as the black Botany-Bay wood, in which the available produce, when it is trimmed ready for the lathe, may be considered to be about one third or fourth of the original weight, sometimes still less; but unfortunately many others approach too nearly to this condition, as a very large proportion of them partake of the imperfections referred to, more especially the cracks; the larger hard woods are by comparison much less wasteful.
All the harder woods require increased care in the seasoning, which is often badly begun by exposure to the sun or hot winds in their native climates: their greater impenetrability to the air the more disposes them to crack, and their comparative scarcity and expense, are also powerful arguments on the score of precaution. It is therefore desirable to prepare them for the transition from the yard or cellar to the turning room, by removing the parts which arc necessarily wasted. the more intimately to expose them to the air, some time before they are placed in the house, and they should be always kept away from the fire, or at first in a room altogether without one.
It is usual to begin by cutting the logs into pieces a few inches or upwards in length, to the general size of the work; and if possible to prepare every piece into a round block, or into two or three, when the wood is irregular, hollow, or cracked. In the latter case, a thin wedge is inserted into the principal crack, and driven down with a wooden maul; or a cleaver such as fig. 7, which has a sharp edge, and a pole to receive the blow, is used in the same manner; these tools, or the hatchet, are likewise used in splitting up the English woods, when they are beyond the diameters required.* The cleft pieces are next roughly trimmed with the hatchet, or else with the paring knife, (fig. 8
over leaf) a tool of safer and more economical application in the hands of the amateur: it is a lever knife, from two and a half to three feet long, the cutting edge is near that end which terminates in a hook, the other extremity has a transverse handle; an eye-bolt for the hook to act against, is screwed into the bench or block, and a detached cutting board is fixed under the blade, to serve as the support for the wood, and for the knife to cut upon. To avoid waste of material, it is advisable, until the eye is well accustomed to the work, to score with the compasses upon each end of the rough block, as large a circle as it will allow, to serve as a guide for the knife.
The block, represented in fig. 8, is adapted to the bearers of the lathe, hut any other support will serve equally well. The paring-knife is also employed for other purposes besides those of the turner: it is sometimes made with a curved edge like a gouge, and is used in many shaping operations in wood, as in the manufacture of shoe-lasts, clogs, pattens, and toys.*
* Sometimes the glazier's chipping knife is used for small pieces of wood instead of the clearer represented. - See also Appendix, Note I., page 953, vol. ii.
In the absence of the paring-knife or hatchet, the work is fixed in the vice, and rounded with a coarse rasp, but this is much less expeditious; by some manufacturers the preparation both of the foreign and English woods is prosecuted still further, by cutting the material into smaller pieces, rough turned and hollowed in the lathe, to the forms of boxes, or other articles for which they are specifically intended, and in fact every measure that tends to make the change of condition gradual, assists also in the economy, perfection, and permanence of the work.
Many of the timber woods are divided at the saw-pit into planks or boards, at an early stage, in order to multiply the surfaces upon which the air may act, and also to leave a less distance for its penetration: after sawing, they should never be allowed to rest in contact, as the partial admission of the air often causes stains or doating: but they are placed either perpendicularly or horizontally in racks, or they are more commonly stacked in horizontal piles, with parallel slips of wood placed between at distances from about three to six or eight feet, according to the quantity of support required; the pile when carefully stacked forms a press and keeps the whole flat and straight.
* A paring-knife similar to the above, but working in a guide, and with an edge 12 or 14 inches long, is a most effective instrument in the hands of the toy-makers. The pieces of birch, alder, etc. are boiled in a cauldron for about an hour to soften them, and whilst hot they may be worked with great expedition and perfection. The workmen pare off slices, the plankway of the grain, as large as 4 by 6 inches, almost as quickly as they can be counted: they are wedged tight in rows, like books, to cause them to dry flat and straight, and they seldom require any subsequent smoothing. In making the little wheels for carts, etc, say of one or two inches diameter, and one-quarter or three-eighths of an inch thick, they cut them the cross-way of the grain, out of cylinders previously turned and bored; the flexibility of the hot moist wood being such, that it yields to the edge of the knife without breaking transversely as might be expected.
Thin pieces will be sufficiently seasoned in about one year's time, but thick wood requires two or three years, before it is thoroughly fit to be removed to the warmer temperature of the house for the completion of the drying. Mahogany, cedar, rosewood, and the other large foreign woods, require to be carefully dried after they are cut into plank, as notwithstanding the length of time that sometimes intervenes between their being felled and brought into use, they still retain much of their moisture whilst they remain in the log.*
In some manufactories the wood is placed for a few days before it is worked up, in a drying-room heated by means of stoves, steam, or hot water, to several degrees beyond the temperature to which the finished work is likely to be subjected.
Such rooms arc frequently made as air-tight as possible, which appears to be a mistake, as the wood is then surrounded by a warm but stagnant atmosphere, which retains whatever moisture it may have evaporated from the wood. Of late a plan has been more successfully practised in seasoning timber for building purposes, by the employment of heated rooms with a free circulation of air, which enters at the lower part in a hot and dry state, and escapes at the upper charged with the moisture which it freely absorbs in the heated condition. The continual ingress of hot dry air, greedy of moisture, so far expedites the drying, that it is accomplished in one-third of the time that is required in the ordinary way in the open air.†
* Scientifically considered, the drying Lb only said to be complete when the wood ceases to lose weight from evaporation; this does not occur after twice or thrice the period usually allowed for the process of seasoning.
In many modern buildings small openings are left through the walls to the external air to allow a partial circulation amidst the beams and joists, as a preservative from decay, and for the entire completion of the seasoning.
† Price's Patent