CHAPTER VIII. - HOW TO MAKE DRAINING TILES.
Draining tiles are made of burnt clay, like bricks and earthen-ware.
In general terms, the process is as follows:—The clay is mixed with sand, or other substances which give it the proper consistency, and is so wetted as to form a plastic mass, to which may be given any desired form, and which is sufficiently stiff to retain its shape. Properly prepared clay is forced through the aperture of a die of the shape of the outside of the tile, while a plug,—held by a support in the rear of the die,—projects through the aperture, and gives the form to the bore of the tile. The shape of the material of the tile, as it comes from the die, corresponds to the open space, between the plug and the edge of the aperture. The clay is forced out in a continuous pipe, which is cut to the desired length by a wire, which is so thin as to pass through the mass without altering the shape of the pipe. The short lengths of pipe are dried in the air as thoroughly as they can be, and are then burned in a kiln, similar to that used for pottery.
Materials.—The range of earths which may be used in the manufacture of tiles is considerable, though clay is the basis of all of them. The best is, probably, the clay[pg 175] which is almost invariably found at the bottom of muck beds, as this is finer and more compact than that which is dug from dry land, and requires but little preparation. There is, also, a peculiar clay, found in some localities, which is almost like quick-sand in its nature, and which is excellent for tile-making,—requiring no freezing, or washing to prepare it for the machine. As a general rule, any clay which will make good bricks will make tiles. When first taken from the ground, these clays are not usually adhesive, but become so on being moistened and kneaded.
It is especially important that no limestone pebbles be mixed with the clay, as the burning would change these to quicklime, which, in slaking, would destroy the tiles. The presence of a limey earth, however, mixed through the mass, is a positive advantage, as in this intimate admixture, the lime forms, under the heat of the kiln, a chemical combination with the other ingredients; and, as it melts more readily than some of them, it hastens the burning and makes it more complete. What is known as plastic clay, (one of the purest of the native clays,) is too strong for tile-making, and must be "tempered," by having other substances mixed with it, to give it a stiffer quality.
The clay which is best for brick-making, contains Silica, and Alumina in about the following proportions:
Silica ... 55 to 75 per cent.
Alumina ... 35 to 25 per cent.
Variable quantities of other materials are usually found in connection with the clay, in its native condition. The most common of these are the following:—
Magnesia 1 to 5 per cent.—sometimes 20 to 30 per cent.
Lime 0 to 19 per cent.
Potash 0 to 5 per cent.
Oxyd of iron 0 to 19 per cent.
"These necessary elements give fusibility to earthenware,[pg 176] and, therefore, allow its constituent substances to combine in such a manner as to form a resisting body; and thus is performed with a temperature lower in proportion as the necessary elements are more abundant."[23]
When the earth of the locality where tiles are to be made is not sufficiently strong for the purpose, and plastic clay can be cheaply obtained from a distance, a small quantity of this may be used to give strength and tenacity to the native material.
The compound must always contain a proper proportion of clay and sand. If too little clay is used, the mass will not be sufficiently tough to retain its compactness as it passes through the die of the tile machine; if too little sand, the moulded tiles will not be strong enough to bear handling, and they will crack and warp in drying and burning. Within the proper limits, the richer earths may be moulded much thinner, and tiles made from them may, consequently, be made lighter for transportation, without being too weak. The best materials for tempering stiff clays are sand, pounded brick or tile, or scoria, from smelting furnaces.
Preparation Of Earths.—The clay from which tiles are to be made, should be thrown out in the fall, (the upper and lower parts of the beds being well mixed in the operation,) and made into heaps on the surface, not more than about 3 feet square and 3 feet high. In this form, it is left exposed to the freezing and thawing of winter, which will aid very much in modifying its character,—making it less lumpy and more easily workable. Any stones which may appear in the digging, should, of course, be removed, and most earths will be improved by being passed through a pair of heavy iron rollers, before they are piled up for the winter. The rollers should be made of cast iron, about 15 inches in diameter, and 30 inches long, and set as close[pg 177] together as they can be, and still be revolved by the power of two horses. The grinding, by means of these rollers, may add 50 cents per thousand to the cost of the tiles, but it will greatly improve their quality.
In the spring, the clay should be prepared for tempering, by the removal of such pebbles as it may still contain. The best way to do this is by "washing," though, if there be only a few coarse pebbles, they may be removed by building the clay into a solid cone 2 or 3 feet high, and then paring it off into thin slices with a long knife having a handle at each end. This paring will discover any pebbles larger than a pea that may have remained in the clay.
Washing is the process of mixing the clay with a considerable quantity of water, so as to form a thin paste, in which all stones and gravel will sink to the bottom; the liquid portion is then drawn off into shallow pits or vats, and allowed to settle, the clear water being finally removed by pumping or by evaporation, according to the need for haste. For washing small quantities of clay, a common mortar bed, such as is used by masons, will answer, if it be supplied with a gate for draining off the muddy water after the gravel has settled; but, if the work is at all extensive, a washing mill will be required. It may be made in the form of a circular trough, with scrapers for mixing the clay and water attached to a circular horse-sweep.
"Another convenient mixing machine may be constructed in the following manner: Take a large hollow log, of suitable length, say five or six feet; hew out the inequalities with an adz, and close up the ends with pieces of strong plank, into which bearing have been cut to support a revolving shaft. This shaft should be sufficiently thick to permit being transfixed with wooden pins long enough to reach within an inch or two of the sides of the log or trough, and they should be so beveled as to form in their aggregate shape an interrupted screw, having a direction[pg 178] toward that end of the box where the mixed clay is designed to pass out. In order to effect the mixing more thoroughly, these pins may be placed sufficiently far apart to permit the interior of the box to be armed with other pins extending toward the center, between which they can easily move. The whole is placed either horizontally or vertically, and supplied with clay and water in proper quantities, while the shaft is made to revolve by means of a sweep, with horse power, running water or steam, as the case may be. The clay is put into the end farthest from the outlet, and is carried forward to it and mixed by the motion, and mutual action and re-action of the pins in the shaft and in the sides of the box. Iron pins may, of course, be substituted for the wooden ones, and have the advantage of greater durability and of greater strength in proportion to their size, and the number may therefore be greater in a machine of any given length. The fluid mass of clay and water may be permitted to fall upon a sieve or riddle, of heavy wire, and afterward be received in a settling vat, of suitable size and construction, to drain off the water and let the clay dry out sufficiently by subsequent evaporation. A machine of this construction may be made of such a size that it may be put in motion by hand, by means of a crank, and yet be capable of mixing, if properly supplied, clay enough to mold 800 or 1000 pieces of drain pipe per day."[24]
Mr. Parkes, in a report to the Royal Agricultural Society of England, in 1843, says:
"It is requisite that the clay be well washed and sieved before pugging, for the manufacture of these tiles, or the operation of drawing them would be greatly impeded, by having to remove stones from the small space surrounding the die, which determines the thickness of the pipe. But it results from this necessary washing, that the substance[pg 179] of the pipe is uniformly and extremely dense, which, consequently, gives it immense strength, and ensures a durability which cannot belong to a more porous, though thicker, tile.
"The clay is brought from the pug-mill so dry that, when squeezed through the machine, not a drop of water exudes,—moisture is, indeed, scarcely apparent on the surface of the raw pipe. Hence, the tiles undergo little or no change of figure while drying, which takes place very rapidly, because of their firm and slight substance."
Fig. 42 - PUG-MILL.
Tempering.—After the fine clay is relieved of the water with which it was washed, and has become tolerably dry, it should be mixed with the sand, or other tempering material, and passed through the Pug-Mill, (Fig. 42,) which will thoroughly mix its various ingredients, and work the whole into a homogeneous mass, ready for the tile machine. The pug-mill is similar to that used in brick-yards, only, as the clay is worked much stiffer for tiles than for bricks, iron knives must be substituted for the wooden pins. These knives are so arranged as to cut the clay in every part, and, by being set at an angle, they force it downward toward the outlet gate at the bottom. The clay should be kept at the proper degree of moisture from the time of tempering, and after passing through the pug-mill it should be thoroughly beaten to drive out the air, and the beaten mass should be kept covered with wet cloths to prevent drying.
Moulding the Tiles.—Machines for moulding tiles are[pg 180] of various styles, with much variation in the details of their construction, but they all act on the same general principle;—that of forcing the clay through a ring-shaped aperture in an iron plate, forming a continuous pipe, which is carried off on an endless apron, or on rollers, and cut by wires into the desired lengths. The plates with the ring-shaped apertures are called dies; the openings are of any desired form, corresponding to the external shape of the tiles; and the size and shape of the bore, is determined by the core or plug, which is held in the centers of the apertures. The construction of the die plates, and the manner of fastening the plugs, which determine the bore of the tiles, is shown in Fig. 43. The view taken is of the inside of the plate.
Fig. 43 - PLATE OF DIES.
The machine consists usually of a strong iron chest, with a hinged cover, into which the clay is placed, having a piston moving in it, connected by a rod or bar, having cog-teeth, with a cog-wheel, which is moved by horse or hand power, and drives the piston forward with steadiness, forcing the clay through the openings in the die-plate. The clay issues in continuous lines of pipe. The machines most in use in this country are connected directly with the pug-mill, and as the clay is pugged, it at once passes into the box, and is pressed out as tiles. These machines are usually run by horse-power.
Mr. Barral, in his voluminous work on drainage,[25] describes, as follows, a cheap hand machine which can be made by any country wheelwright, and which has a capacity of 3,000 tiles per day (Fig. 44):
"Imagine a simple, wooden box, divided into two compartments. In the rear compartment there stands a vertical post, fastened with two iron bolts, having heads[pg 181] at one end, and nuts and screws at the other. The box is thus fixed to its support. We simply place this support on the ground and bind its upper part with a rope to a tree, a stake, or a post. The front compartment is the reservoir for the clay, presenting at its front an orifice, in which we fix the desired die with a simple bolt. A wooden piston, of which the rod is jointed with a lever, which works in a bolt at the top of the supporting post, gives the necessary pressure. When the chest is full of clay, we bear down on the end of the lever, and the moulded tiles run out on a table supplied with rollers. Raising the piston, it comes out of the box, which is again packed with clay. The piston is replaced in the box; pressure is again applied to the lever, and so on. When the line of tiles reaches the end of the table, we lower a frame on which brass wires are stretched, and cut it into the usual lengths."
Fig. 44 - CHEAP WOODEN MACHINE.
The workmen must attend well to the degree of moisture of the clay which is put into the machine. It should be dry enough to show no undue moisture on its surface as it comes out of the die-plate, and sufficiently moist not[pg 182] to be crumbled in passing the edge of the mould. The clay for small (thin) tiles must, necessarily, be more moist than that which is to pass through a wider aperture; and for the latter there may, with advantage, be more sand in the paste than would be practicable with the former.
After the tiles are cut into lengths, they are removed by a set of mandrils, small enough to pass easily into them, such as are shown in Fig. 45, (the number of fingers corresponding with the number of rows of tiles made by the machine,) and are placed on shelves made of narrow strips sawn from one-inch boards, laid with spaces between them to allow a free circulation of air.
Fig. 45 - MANDRIL FOR CARRYING TILES FROM MACHINE.
Drying and Rolling.—Care must be taken that freshly made tiles be not dried too rapidly. They should be sheltered from the sun and from strong winds. Too rapid drying has the effect of warping them out of shape, and, sometimes, of cracking the clay. To provide against this injury, the drying is done under sheds or other covering, and the side which is exposed to the prevailing winds is sometimes boarded up.
For the first drying, the tiles are placed in single layers on the shelves. When about half dried,—at which time they are usually warped more or less from their true shape,—it is well to roll them. This is done by passing through them a smooth, round stick, (sufficiently smaller than the bore to enter it easily, and long enough to project five or six inches beyond each end of the tile,) and,—holding one end of the stick in each hand,—rolling them carefully on a table. This operation should be performed when the tiles are still moist enough not to be broken by the slight bending required to make them straight. After rolling, the tiles may be piled up in close layers, some[pg 183] four or five feet high, (which will secure them against further warping,) and left until they are dry enough for burning,—that is, as dry as they can be made by exposure to the air.
Burning.—Tiles are burned in kilns in which, by the effect of flame acting directly upon them, they are raised to a heat sufficient to melt some of their more easily fusible ingredients, and give to them a stone-like hardness.
Kilns are of various construction and of various sizes. As this book is not intended for the instruction of those who are engaged in the general manufacture of tiles, only for those who may find it necessary to establish local works, it will be sufficient to describe a temporary earthen kiln which may be cheaply built, and which will answer an excellent purpose, where only 100,000 or 200,000 tiles per season will be required.
Directions for its construction are set forth in a letter from Mr. T. Law Hodges, of England, to the late Earl Spencer, published in the Journal of the Royal Agricultural Society for the year 1843, as follows:
"The form of the clay-kiln is circular, 11 feet in diameter, and 7 feet high. It is wholly built of damp, clayey earth, rammed firmly together, and plastered, inside and out, with loam (clay?). The earth to form the walls is dug out around the base, leaving a circular trench about four feet wide and as many deep, into which the fire-holes of the kiln open. If wood be the fuel used, three fire-holes will be sufficient; if coal, four will be needed. About 1,200 common brick will be wanted to build these fire-holes and flues; if coal is used, rather fewer bricks will be wanted, but, then, some iron bars are necessary,—six bars to each fire-hole.
"The earthen walls are four feet thick at the floor of the kiln, seven feet high, and tapering to a thickness of two feet at the top; this will determine the slope of the[pg 184] exterior face of the kiln. The inside of the wall is carried up perpendicularly, and the loam plastering inside becomes, after the first burning, like a brick wall. The kiln may be safely erected in March, or whenever the danger of injury from frost is over. After the summer use of it, it must be protected, by faggots or litter, against the wet and frost of winter. A kiln of these dimensions will contain 32,500 1-1/4-inch tiles, * * * or 12,000 2-1/4-inch tiles. * * *
"In good weather, this kiln can be filled, burnt, and discharged once in every fortnight, and fifteen kilns may be obtained in a good season, producing 487,500 1-1/4-inch tiles, and in proportion for the other sizes.
"It requires 2 tons 5 cwt. of good coals to burn the above kiln, full of tiles."
Fig. 46 - CLAY-KILN.
A sectional view of this kiln is shown in Fig. 46, in which C, C represent sections of the outer trench; A, one of the three fire-holes; and B, B, sections of a circular passage inside of the wall, connected with the fire-holes, and serving as a flue for the flames, which, at suitable intervals, pass through openings into the floor of the kiln. The whole structure should be covered with a roof of rough boards, placed high enough to be out of the reach of the fire. A door in the side of the kiln serves for putting[pg 185] in and removing the tiles, and is built up, temporarily, with bricks or clay, during the burning. Mr. Hodges estimates the cost of this kiln, all complete, at less than $25. Concerning its value, he wrote another letter in 1848, from which the following is extracted:
"The experience of four years that have elapsed since my letter to the late Earl Spencer, published in the 5th volume of the proceedings of the Royal Agricultural Society, page 57, has thoroughly tested the merits of the temporary clay-kilns for the burning of draining-pipes described in that letter.
"I am well aware that there were persons, even among those who came to see it, who pronounced at once upon the construction and duration of the kiln as unworthy of attention. How far their expectations have been realized, and what value belongs to their judgment, the following short statement will exhibit:
"The kiln, in question, was constructed, in 1844, at a cost of £5.
"It was used four times in that year, burning each time between 18,000 and 19,000 draining pipes, of 1-3/4 inches in diameter.
"In 1845, it was used nine times, or about once a fortnight, burning each time the same quantity of nearly 19,000 pipes.
"In 1846, the same result.
"In 1847, it has been used twelve times, always burning the same quantity. In the course of the last year a trifling repair in the bottom of the kiln, costing rather less than 10 shillings, was necessary, and this is the only cost for repair since its erection. It is now as good as ever, and might be worked at least once a fortnight through the ensuing season.
"The result of this experiment of four years shows not only the practical value of this cheap kiln, but Mr. Hatcher, who superintends the brick and tile-yard at Benenden,[pg 186] where this kiln stands, expresses himself strongly in favor of this kiln, as always producing better and more evenly burned pipes than either of his larger and better built brick-kilns can do."
The floor of the kiln is first covered with bricks, placed on end, at a little distance from each other, so as to allow the fire to pass between them, and the tiles are placed on end on these. This position will afford the best draft for the flames. After the kiln is packed full, the door-way is built up, and a slow fire is started,—only enough at first to complete the drying of the tiles, and to do this so slowly as not to warp them out of shape. They will be thoroughly dry when the smoke from the top of the kiln loses its dark color and becomes transparent. When the fires are well started, the mouths of the fire-holes may be built up so as to leave only sufficient room to put in fresh fuel, and if the wind is high, the fire-holes, on the side against which it blows, should be sheltered by some sort of screen which will counteract its influence, and keep up an even heat on all sides.
The time required for burning will be from two days and a night to four days and four nights, according to the dryness of the tiles, the state of the weather, and the character of the fuel. The fires should be drawn when the tiles in the hottest part of the kiln are burned to a "ringing" hardness. By leaving two or three holes in the door-way, which can be stopped with loose brick, a rod may be run in, from time to time, to take out specimen tiles from the hottest part of the kiln, which shall have been so placed as to be easily removed. The best plan, however,—the only prudent plan, in fact,—will be to employ an intelligent man who is thoroughly experienced in the burning of brick and pottery, and whose judgment in the management of the fires, and in the cooling off of the kiln, will save much of the waste that would result from inexperienced management. After the burning is completed, from[pg 187] 40 to 60 hours must be allowed for the cooling of the kiln before it is opened. If the cold air is admitted while it is still very hot, the unequal contraction of the material will cause the tiles to crack, and a large portion of them may be destroyed.
If any of the tiles are too much burned, they will be melted, and may stick together, or, at least, have their shape destroyed. Those which are not sufficiently burned would not withstand the action of the water in the soil, and should not be used. For the first of these accidents there is no remedy; for the latter, reburning will be necessary, and under-done tiles may be left, (or replaced,) in the kiln in the position which they occupied at the first burning, and the second heat will probably prove sufficient. There is less danger of unequal burning in circular than in square kilns. Soft wood is better than hard, as making a better flame. It should be split fine, and well seasoned.
Arrangement of the Tilery.—Such a tilery as is described above should have a drying shed from 60 to 80 feet long, and from 12 to 18 feet wide. This shed may be built in the cheapest and roughest manner, the roof being covered with felting, thatch, or hemlock boards, as economy may suggest. It should have a tier of drying shelves, (made of slats rather than of boards,) running the whole length of each side. A narrow, wooden tram-way, down the middle, to carry a car, by which the green tiles may be taken from the machine to the shelves, and the dry ones from the shelves to the kiln, will greatly lessen the cost of handling.
The pug-mill and tile-machine, as well as the clay pit and the washing-mill, should be at one end of the shed, and the kiln at the other, so that, even in rainy weather, the work may proceed without interruption. A shed of the size named will be sufficient to dry as many tiles of[pg 188] assorted sizes as can be burned in the clay-kiln described above.
The Cost of Tiles.—It would be impossible, at any time, to say what should be the precise cost of tiles in a given locality, without knowing the prices of labor and fuel; and in the present unsettled condition of the currency, any estimate would necessarily be of little value. Mr. Parker's estimated the cost of inch pipes in England at 6s., (about $1.50,) per thousand, when made on the estate where they were to be used, by a process similar to that described herein. Probably they could at no time have been made for less than twice that cost in the United States,—and they would now cost much more; though if the clay is dug out in the fall, when the regularly employed farm hands are short of work, and if the same men can cut and haul the wood during the winter, the hands hired especially for the tile making, during the summer season, (two men and two or three boys,) cannot, even at present rates of wages, bring the cost of the tiles to nearly the market prices. If there be only temporary use for the machinery, it may be sold, when no longer needed, for a good percentage of its original cost, as, from the slow movement to which it is subjected, it is not much worn by its work.
There is no reason why tiles should cost more to make than bricks. A common brick contains clay enough to make four or five 1-1/4-inch tiles, and it will require about the same amount of fuel to burn this clay in one form as in the other. This advantage in favor of tiles is in a measure offset by the greater cost of handling them, and the greater liability to breakage.
The foregoing description of the different processes of the manufacture of draining tiles has been given, in order that those who find it necessary, or desirable, to establish works to supply the needs of their immediate localities may commence their operations understandingly, and form[pg 189] an approximate opinion of the promise of success in the undertaking.
Probably the most positive effect of the foregoing description, on the mind of any man who contemplates establishing a tilery, will be to cause him to visit some successful manufactory, during the busy season, and examine for himself the mode of operation. Certainly it would be unwise, when such a personal examination of the process is practicable, to rely entirely upon the aid of written descriptions; for, in any work like tile-making, where the selection, combination and preparation of the materials, the means of drying, and the economy and success of the burning must depend on a variety of conditions and circumstances, which change with every change of locality, it is impossible that written directions, however minute, should be a sufficient guide. Still, in the light of such directions, one can form a much better idea of the bearing of the different operations which he may witness, than he could possibly do if the whole process were new to him.
If a personal examination of a successful tilery is impracticable, it will be necessary to employ a practical brick-maker, or potter, to direct the construction and operation of the works, and in any case, this course is advisable.
In any neighborhood where two or three hundred acres of land are to be drained, if suitable earths can be readily obtained, it will be cheaper to establish a tile-yard, than to haul the necessary tiles, in wagons, a distance of ten or twenty miles. Then again, the prices demanded by the few manufacturers, who now have almost a monopoly of the business, are exorbitantly high,—at least twice what it will cost to make the tiles at home, with the cheap works described above, so that if the cost of transportation on the quantity desired would be equal to the cost of establishing the works, there will be a decided profit in the home manufacture. Probably, also, a tile-yard, in a neighborhood where the general character of the soil is[pg 190] such as to require drainage, will be of value after the object for which it was made has been accomplished.
While setting forth the advantage to the farmer of everything which may protect him against monopolies, whether in the matter of draining-tile, or of any other needful accessory of his business, or which will enable him to procure supplies without a ruinous outlay for transportation, it is by no means intended that every man shall become his own tile-maker.
In this branch of manufacture, as in every other, organized industry will accomplish results to which individual labor can never attain. A hundred years ago, when our mill-made cloths came from England, and cost more than farmers could afford to pay, they wore home-spun, which was neither so handsome nor so good as the imported article; but, since that time, the growing population and the greater demand have caused cloth mills to be built here, greater commercial facilities have placed foreign goods within easy reach, and the house loom has fallen into general disuse.
At present, the manufacture of draining tiles is confined to a few, widely separated localities, and each manufacturer has, thus far, been able to fix his own scale of charges. These, and the cost of transportation to distant points, make it difficult, if not impossible, for many farmers to procure tiles at a cost low enough to justify their use. In such cases, small works, to supply local demand, may enable many persons to drain with tiles, who, otherwise, would find it impossible to procure them cheaply enough for economical use; and the extension of under-draining, causing a more general acquaintance with its advantages, would create a sufficient demand to induce an increase of the manufacture of tiles, and a consequent reduction of price.