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.