CHAPTER XXIV
THE MANUFACTURE OF CHARCOAL
Amongst dead or dying industries of our woodlands that have been revived by the war, none is at present receiving a greater share of attention than the manufacture of charcoal.
There was a time, and not so long ago, when the merry voice and ring of the charcoal burner’s axe were familiar sounds in some of the Kentish and other forests of Southern England; but keen foreign competition, aided by preferential carriage rates, have caused this time-honoured industry to slip from our hands; indeed, it was almost forgotten till again called into existence for the battlefields of France and Flanders. The trenches must be warmed without apprising the enemy of the existence of our men, and in order to do this and prevent soaring signals of smoke, the tent brazier is filled with glowing charcoal.
Except, perhaps, in Kent and Surrey and the English Lake district, where small quantities of charcoal are annually produced for the hop kilns and iron smelting, charcoal burning is a thing of the past. The expert charcoal burner is now a difficult man to find, and an independent, highly-paid workman when you have found him. Successive members of the same family in Kent have been known to follow the occupation of charcoal burning for fully a century and a half, and it is distinctly a skilled industry, and confined to few.
Usually the men work in threes, and, having selected a piece of ground sheltered from the prevailing winds and in a position to which easy access with wood can be obtained, a rough hut is erected for the accommodation of these nocturnal workmen. Water, sand or sawdust and turf are other requisites that must be provided as the work proceeds. A couple of large tarpaulins and half a dozen straw-covered hurdles are other necessities.
From the point of economy in carting the wood to the kilns it may seem that shifting the position of burning from one part of the woodland to another is to be recommended. Such is, however, not the case, as the hard, dry, ash-covered site, where charring has already been carried out, has its advantages, and the cost of transferring the workmen’s hut and tools from one position to another must also be considered.
Several methods, largely dependent on the quantity and quality of charcoal to be obtained, are adopted, but in order to procure that of the best description the following system, which has been successfully carried out on a large estate for the past hundred years at least, is recommended. The timber carted to the charcoal yard consists of all kinds of hardwoods, preferably not under two inches in diameter.
Firewood and rough, unsaleable timber, as also inferior grades of heavy coppice wood, are mainly utilized for the production of charcoal. The wood is sawn into pieces about 2 ft. long, this being the most convenient size for building the kiln, and these again split if required to some 4 in. to the side, and when a sufficient quantity for two pits has been cut up, the building of these is proceeded with. It has been found economical to burn two pits at the same time, as both can be attended to as conveniently as one, and it is unnecessary for the men to sit up at night to watch each separately. The charcoal pits, one of which is shown in the accompanying sketch, are made of a broadly conical shape, 21 ft. in diameter and about 9 ft. high, and the mode of construction is as follows:—
A strong stake is driven firmly into the ground and left protruding about a foot. Around this are placed small pieces of dry ash of equal length, and standing as close to the upright stake as possible; around this another layer is placed in the same manner, and this is continued until a circle 5 ft. in diameter is obtained. A circle 1 ft. in diameter, and having the top of the stake previously driven into the ground as centre, is next made by placing the wood horizontally on the upright pieces and side by side, the ends of each piece being placed at the circumference of the circle already made, and directed towards its centre. Layer upon layer is built in this manner until the pit is of the required height, the wood used here being dry pieces of ash 2 ft. in length, but split rather smaller than the ordinary pieces. A sort of chimney is thus formed, by means of which the pit is fired. Outside the core the wood is placed on end and reclining inwards, this being continued until the pits are of the required size. When the building is completed the pits are covered with newly cut turf, the grassy side placed innermost, beginning at the base and working towards the top, each line of turf overlapping the previous one by a few inches. The circular hole or chimney is left open for firing. Before turfing the top half of each pit it is carefully examined, and any crevices between the wood packed full of small pieces of turf and sawdust to exclude the air. The turfs are cut about 1 ft. in width, and of any convenient length. The quantity required for two pits of the dimensions stated is seven loads.
When the pit is satisfactorily covered it is fired by dropping a couple of shovelfuls of burning wood and some dry pieces of pine or ash into the opening left at the top; the top turf is then put on, which effectually shuts up the chimney, and the process of charring commences. The smoke is first seen issuing from the lower half of each pit, where the chinks were not packed with sawdust, and ultimately it escapes from the whole surface.
Constant attention is required day and night during the period of burning, especially should the weather be stormy, as the wind, by striking on a particular part of the pit, causes that side to burn more rapidly, and fall in. When this occurs the hole must at once be filled in with rough logs, which had been set aside for the purpose when splitting the wood, and re-covered with turf.
When the weather is mild the pits burn uniformly, require but little attention, and produce the finest charcoal. The time required for burning will vary with the size of the pit, quality of wood, method of covering, and meteorological conditions. From six to seven days are usually required for pits of the above dimensions, but smaller kilns only covered with grass, fern and a little soil may be ready for uncovering in from two to four days. Long experience has, however, proved that by the slower process of charring the best charcoal is produced, but the cost is higher. By covering the pits with grass and fern, as is often done, a considerable saving is no doubt effected, but where turf is available there can be no question as to its value over the former, and on the boundaries of most woodlands it is readily procurable at the cost of cutting. As the charring proceeds the turf gradually disappears until only a slight covering of burnt earth remains. When the pits have burned out and become cool, it is found that they are reduced to rather less than half their original size.
[Illustration: SECTION OF CHARCOAL PIT]
The charcoal is extracted by means of a specially constructed rake resembling a light drag, but having much finer teeth, which, after it has become quite cold, is stored in a shed until required for use.
The very finest charcoal, superior to what is generally sold, is produced by this method. The expenses connected with making it are, however, a little heavier than usual, owing to the slower system of charring, the use of larger wood, and the extra cost of covering with turf. As to the cost of producing charcoal by the above method, this will vary greatly, much depending on the distance the wood has to be carted and on the cost of labour in the particular district.
The price paid to the charcoal burners is 7_d._ per bushel, or about four guineas per ton, which may seem high, but when we consider that it is specialized work that is confined to few and attended with grave risks and discomfort, the amount earned is not excessive. It should also be remembered that, previous to lighting the kilns, sufficient rough, not corded, wood has to be sawn and split and the pits carefully built and covered, not to speak of the constant attention required, both day and night, wet or dry, for from three to seven days, during charring process. The usual price for burning charcoal when the wood is corded is 35_s._ per ton.
Fresh-felled wood is rarely converted into charcoal, the greater portion of that used being thinnings of the previous season. The proportion of wood to charcoal varies greatly, much depending on the size, quality, and maturity of timber. Having had occasion to purchase charcoal lately, I found the price, retail, to be 2_s._ 6_d._ per bushel, or in quantities of not less than a ton, £14, for that of fair quality.
From about the twelfth century onwards Scotland, where wood was abundant, produced annually a large quantity of charcoal iron; and in 1660 the Navy Commissioners nominated John Evelyn to investigate the then denudation of forests owing to the manufacture of charcoal for iron smelting, and the following quaint extract from his report will be interesting:—“Nature has thought fit to produce this wasting ore more plentifully in woodlands than any other point, and to enrich our forests to their own destruction—a deep execration of iron mills and ironmasters also.” The Lorn Works, in Argyllshire, were started in 1753, and annually consumed upwards of 3,000 tons of lump charcoal.
The Sussex and Kentish forests at one time supported many of the familiar charcoal burners, and right brawny and thrifty were these denizens of the woodland with their rustic wooden huts and piles of rifted firewood, but the industry was almost a thing of the past till again called into active existence by the exigencies of the war.
=Kiln burning.=—The kiln is made of brick, one course being sufficient, if bands of iron be added to strengthen the brickwork. It is usually conical in shape, 24 ft. in diameter, with an equal height, and holds about forty cords of wood. The wall of the kiln is carried up nearly straight for about 6 ft., when it is gradually drawn in and made a blunt cone shape. A plate of iron is fastened on the top in the manner of a stone to an arch. Three-inch hoop-iron bands, about an eighth of an inch thick, are placed around the kiln and drawn together by means of screw-bolts and nuts. At the base, and near the top, are double sheet-iron doors, by which it is filled with wood or emptied of charcoal. The time required to fill, burn and empty is about three weeks. Pit-burning, for estate purposes, is, however, most commonly pursued, and has this advantage—that the charcoal can be made at any place where timber is being felled, without extra expense, save that of the cartage of the charcoal, whereas in using the kiln or retort the wood must, in most cases, be conveyed to the place where it is erected.
=Comparative Value of Woods for Charcoal making.=—Amongst home-grown timber, oak, ash, and beech are generally preferred for charcoal making, but the following table will show pretty correctly the proportionate relative values of the various descriptions of wood for gunpowder charcoal:—
Per Cent. Rhamnus frangula contains 27 Laburnum 25 Boxwood 24 Sweet Chestnut 23 Oak 22 Holly 20 Walnut 20 Beech 19 Sycamore 19 Elm 19 Willow 18 Poplar 18 Birch 17 Alder 17 Ash 17 Hazel 17 Mountain Ash 17 Scotch fir 16 Larch 16
=Uses of Charcoal.=—The uses of charcoal for estate purposes are very numerous, for horticultural, agricultural and other departments. From remote antiquity charcoal has been used as a fuel, and for many purposes it is still unsurpassed. It is by far the cleanest solid fuel known; it burns steadily, gives out a great amount of heat, and lasts well. On account of its smokelessness it is invaluable for cookery, and it is also admirably suited for use in green-house and other stoves. It is not adopted for heating apartments on account of the poisonous gas (carbonic oxide) produced in its combustion, and the danger, most apparent when the charcoal is burnt in an open chauffer, is not obviated by using it in a stove, as carbonic oxide has the power of diffusing through red-hot iron.
In gardening, charcoal is largely used for potting purposes, for vine borders, and for flower beds; and in the form of dust it is the best material for packing bulbs for transmission to a distance.
Perhaps the most important of the uses to which charcoal can be put about a house or estate is that depending on its extraordinary power of absorbing gases. It is a perfect deodorant, a preservative of food and all animal substances and a valuable disinfectant. The gases most readily absorbed by charcoal are those which are most prejudicial to health and most frequently produced by putrefactive changes.
In the pores of the charcoal they are destroyed by union with the oxygen condensed from the air. The fact of its being absolutely non-poisonous and perfectly odourless puts it before all other disinfectants.
=“Dogwood” for Gunpowder Charcoal.=—The alder buckthorn, berry-bearing or black alder (_Rhamnus frangula_) is a native shrub that is fairly plentiful in Southern England, though rare in Scotland and Ireland. Confusion sometimes arises from the same popular name being applied to widely different species of plants, and this, unfortunately, is the case with the shrub in question. What is known among gunpowder manufacturers as dogwood is in reality the present shrub (_Rhamnus_), which, however, is quite distinct from the true dogwood (_Cornus_) and belongs to an entirely different family. To those who contemplate growing charcoal wood for the making of explosives, this distinction is of the utmost importance, as I have seen _Cornus sanguinea_ cultivated for the making of gunpowder.
The alder buckthorn is perfectly hardy, growing freely even in the North of Scotland, where it ripens its seeds. It is usually found as an erect-growing bush from 8 ft. to 10 ft. in height, though in suitable situations in Southern England specimens fully 20 ft. high, with stems 6 in. in diameter, are to be met with. The bright green leaves are oval in shape and vary, according to conditions of growth, from 2 in. to 3 in. in length, while the flowers are of a dull yellowish green and are succeeded by dark purple berries each about the size of a pea. From a very early date the alder buckthorn has been cultivated, though not extensively, in this country for charcoal making, and the price, upwards of £15 per ton, that is paid for the wood, shows that the growing of this shrub is a profitable undertaking. At one time large quantities of the wood were produced in Sussex and other counties, the selling price being £14 per ton when peeled and tied in bundles.
The cultivation of the alder buckthorn is nearly similar to that of the osier for basket-making, and the produce is dealt with and disposed of in like manner. For soil any good loam inclined to be dampish will suit it well, and an open, but not wind-swept, situation should be chosen for its cultivation. The land intended for growing the alder buckthorn should be trenched the winter before planting, and a top-dressing of leaf soil or thoroughly decomposed manure, the former preferably, will greatly assist the growth of the young plants and prevent too speedy evaporation of moisture from the soil. Young plants are not offered in quantity in our nursery catalogues, and in order to obtain a stock sufficient to form a plantation, seed-sowing or layering old plants must be resorted to. Fortunately, by either method the plant is readily obtained in quantity, and as the seeds are produced in fair abundance and ripen freely this method of getting up a stock is to be recommended.
The berries, after being collected in the early winter, are treated much as we treat those of the yew and holly. They are mixed with sand in order to separate the seed and fleshy covering, and the whole is sown during early spring in previously prepared beds. The seed beds may be prepared in any shady situation out of doors, the soil being largely composed of light sandy loam mixed with finely riddled leaf-mould. Sometimes the seeds are sown in boxes and placed in a cool frame, but we have found cultivation out of doors more satisfactory. When two years old, the seedlings should be transplanted into lines 18 in. apart and 9 in. from plant to plant. Here they may remain for another two years, after which they should be planted out permanently and headed back the following season. Rather thick final planting is to be recommended, as the shrub being of upright growth, requires comparatively small room for development, and the best wands are produced by a close order of growth, say 5 ft. from plant to plant.
Layering does not produce such upright-habited shrubs as those grown from seed, and the yield of wood per acre under exactly similar conditions of growth is greatly in favour of seedlings.
After planting, the ground should be kept free from rough-growing seeds for the first two years, the crop being cut at from six to seven years’ growth, when the wands are from 1½ in. to 2 in. diameter at butt end. Cutting and bundling is usually done by contract, but, as with the osier, it is imperative that the crop be cut over near ground level and short “stumps” without “spurs” encouraged.
As in the case of ordinary coppice wood, the buckthorn for charcoal making may be cut every sixth or seventh year, the straightest shoots when sorted in about 5 ft. lengths being tied in bundles which are about a yard in girth. The buckthorn being a gross feeder, manuring the land after the removal of a crop has been found advantageous.
Although largely imported from Holland, and other parts of the Continent, home-grown wood is preferred, as it produces a much superior charcoal for the manufacture of explosives. Unfortunately, however, home supplies are so limited that foreign wood is imported in considerable quantity, and as there was a scarcity before the war, the probabilities are that, with our greatly increased consumption of charcoal explosives, a dearth of suitable wood is now being felt.
With the present small remuneration attaching to the cultivation of coppice or underwood, which under ordinary circumstances does not exceed £4 per acre, the cultivation of the alder buckthorn is to be recommended, particularly as the price is at least quadrupled. The cultivation of this is quite simple, while the quality of soil required need not be better than that which produces a crop of chestnut or hazel. In cultivating the alder buckthorn for charcoal purposes the following rules should be observed:—
1. It will not succeed satisfactorily in sandy, poor or water-logged soils; rich, well-manured loam being preferred.
2. The ground should either be trenched or ploughed and cleared of all rough-growing weeds the winter before planting.
3. Plant seedlings or layers in the spring in lines about 5 ft. apart and the same distance from plant to plant.
4. An annual clearance of weeds and loosening of the soil between the rows of plants is recommended where a heavy crop is expected.
5. Induce the growth of stout clean shoots by liberal feeding and clean cultivation.
6. Cut the shoots close to the ground so as to prevent the formation of long spurs and minimize the number of off-shoots. Clean cutting with a sharp tool is imperative.
7. After the removal of a crop, stirring and enriching the soil is to be recommended.
8. Though found mixed with undershrubs and in the shade of trees when in a wild state, yet the greatest quantity of the most valuable wood for charcoal making is produced in open situations.