Chapter 5

The Assyrians and Babylonians made almost exclusive use of brickwork in erecting the vast piles of buildings the shapeless ruins of which mark the site of ancient Nineveh and of the cities of the valley of the Euphrates. Their bricks, it is believed, were entirely sun-dried, not burnt to fuse or vitrify them as ours are, and they have consequently crumbled into mere mounds. The Assyrians also used fine clay tablets, baked in the fire--in fact, a kind of terra cotta--for the purpose of records, covering these tablets with beautifully executed inscriptions, made with a pointed instrument while the clay was soft, and rendered permanent by burning. We don't know much about Greek brickwork; but it is probable that very little brick, if any, was made or used in any part of Greece, as stone, marble, and timber abound there; but the Romans made bricks everywhere, and used them constantly. They were fond of mixing two or more materials together, as for example building walls in concrete and inserting brickwork at intervals in horizontal layers to act as courses of bond. They also erected buildings of which the walls were wholly of brick. They turned arches of wide span in brickwork; and they frequently laid in their walls at regular distances apart courses of brick on edge and courses of sloping bricks, to which antiquaries have given the name of herring-bone work.

The Roman bricks are interesting as records, for it was customary to employ the soldiers on brick making, and to stamp the bricks with names and dates; and thus the Roman bricks found in this country give us some information as to the military commanders and legions occupying different parts of England at different periods. Flue bricks, for the passage of smoke under floors and in other situations, are sometimes found. The Roman brick was often flat and large--in fact, more like our common paving tiles, known as foot tiles, only of larger size than like the bricks that we use. They vary, however, in size, shape, and thickness. Not a few of them are triangular in shape, and these are mostly employed as a sort of facing to concrete work, the point of the triangle being embedded in the concrete and the broad base appearing outside. After the Roman time, brick making seems to have almost ceased in England for many centuries.

It is true we find remains of a certain number of massive brick buildings erected not long after the Norman conquest; but on examination it turns out that these were put up at places where there had been a Roman town, and were built of Roman bricks obtained by pulling down previous buildings. The oldest parts of St. Albans Abbey and portions of the old Norman buildings at Colchester are examples of this sort. Apparently, timber was used in this country almost exclusively for humble buildings down to the 16th century. This is not surprising, considering how well wooded England was; but stone served during the same period for important buildings almost to the exclusion of brick. This is more remarkable, as we find stone churches and the ruins of stone castles in not a few spots remote from stone quarries, and to which the stone must have been laboriously conveyed at a time when roads were very bad and wheel carts were scarce.

About the time of the Tudors, say the reign of Queen Elizabeth, the making of bricks was resumed in England, and many dwelling houses and some few churches were built of good brickwork in that and succeeding reigns. We find in such buildings as Hampton Court Palace, St. James' Palace, and Chelsea Hospital examples of the use of brickwork in important buildings near London at later dates. The fire of London, in 1666, gave a sudden check to the use of timber in house building in the metropolis. Previous to that date the majority of houses had been of a sort the most ornamental examples of which were copied in "Old London" at the Colonial Exhibition. The rebuilding after the fire was largely in brick; and in the suburbs, in the latter part of the 17th and the 18th centuries, many dignified square brick mansions, with bold, overhanging eaves and high roofs and carved ornaments, entered through a pair of florid wrought iron high gates, were built, some few of which still linger in Hampstead and other suburbs. The war time at the beginning of this century was a trying time for builders, with its high prices and heavy taxes, and some of the good-looking brick buildings of that day turn out to have been very badly built when they are pulled about for alterations. With the rapid, wonderful increase in population and wealth in this metropolis during the last 50 years a vast consumption of bricks has taken place, and a year or two back it was reported by the commissioners of police that the extensions of London equaled in a year 70 miles of new house property, practically all of brick. Brick were heavily taxed in the war time which I have referred to, and the tax was levied before burning.

There was a maximum size for the raw brick, which it was supposed served to keep bricks uniform, and the expectation was entertained that when the duty came off, many fancy sizes of bricks would be used. This has not, however, turned out to be the case. The duty has been taken off for years; but the differences in the size of bricks in England are little more than what is due to the different rate of shrinkage of brick earth under burning. It must not, however, be supposed that they have always, and in all countries, been of about the same dimensions.

The size and proportions of bricks have varied extremely in different countries and in the same country at different periods. Some bricks of unusual shapes have also been employed from time to time. Other countries besides England possess districts which from various circumstances have been more or less densely built on, but do not yield much stone or timber; and, accordingly, brickwork is to be met with in many localities. Holland and Belgium, for example, are countries of this sort; and the old connection between Holland and England led to the introduction among us, in the reign of William III., of the Dutch style of building, which has been in our own day revived under the rather incorrect title of Queen Anne architecture. Another great brick district exists on the plains of Lombardy and the northern part of Italy generally, and beautiful brickwork, often with enrichments in marble, is to be found in such cities as Milan, Pavia, Cremona, and Bologna.

Many cities and towns in Northern Germany are also brick built, and furnish good examples of the successful treatment of the material. In some of these German buildings, indeed, very difficult pieces of construction, such as we are in the habit of thinking can only be executed in stone, are successfully attempted in brick. For example, they execute large tracery windows in this material. Great brick gables, often with the stepped outline known as crows' feet, are an excellent architectural feature of these German brick-built towns. In parts of France, also, ornamental brickwork was from time to time made use of, but not extensively. It is not necessary to go very minutely into the manufacture of bricks; but perhaps I ought to say a word or two on the subject. Good brick earth is not simple clay, but a compound substance; and what is essential is that it should burn hard or, in other words, partly vitrify under the action of heat. The brick earth is usually dug up in the autumn, left for the frosts of winter to break it up, and worked up in the early spring.

The moulding is to a very large extent done by hand, sometimes in a wet mould, sometimes in a dry sanded mould, and the bricks are first air-dried, often under some slight shelter, as the rain or frost damages them when fresh made; and then, when this process has made them solid enough to handle, they are burned, and sorted into qualities. The ordinary or stock brick of London and the neighborhood presents a peculiarity the origin of which is not known, and which is not met with, so far as I know, in other parts. Very fine coal or cinders is mixed with the brick earth, and when the bricks are fired these minute particles of fuel scattered through the material all of them burn, and serve to bake the heart of the brick. Stock bricks are burnt in a clamp made of the raw bricks themselves with layers of fuel, and erected on earth slightly scooped out near the middle, so that as the bricks shrink they drop together, and do not fall over sideways.

Most other varieties of bricks are kiln burnt. A very large number of inventions for making bricks by machinery have been patented. If you have occasion to look through the specifications of these patents, you will find four or five main ideas appearing and reappearing, and only here and there an invention which is to some extent different from the others. A great majority of these inventions include machinery for preparing the clay or brick earth, so that it may be dug up and filled into a receptacle and worked up, screened from pebbles, and made fit for use in a short time, so as not to have to wait a whole winter. This is done in some sort of pug mill. A pug mill is a machine consisting of a large cylinder with a central shaft passing through it from top to bottom. Knives or blades are arranged spirally on the shaft, and other blades project into the interior of the cylinder from the walls of it. The material, after being screened, is fed into this at the top, and properly moistened. The shaft is caused to rotate, and the blades divide and subdivide the material, forcing it always downward, so that it at last escapes at the bottom of the pug mill in a continuous stream of moist, well worked up clay, issuing with some force. In one type of machine this clay stream is forced through a square orifice, from which it comes out of the section of a brick, and by a knife or wire or some other means it is cut into lengths.

In another type of machine there is a large revolving drum working on a horizontal axis, with open moulds all round its edge. The clay enters these moulds, and there is an arrangement of plungers by which it is first compressed within the mould and then forced out on to an endless band or some other contrivance that receives it. A third type of machine has the moulds in the flat top of a revolving table, which, as it turns, carries each mould in succession first to a part where it is filled from the pug mill, next to where its contents are compressed, and lastly to where they are pushed out for removal. However made, the brick, when moulded, dried, and burnt, and ready for market, belongs to some one sort, and is distinguished from other sorts by its size, color, quality, and peculiarities.

The sorts of brick that are to be met with in the London market are very varied. To enumerate them all would make a tedious list; to describe them all would be equally tedious. I will endeavor, however, to give some idea of the most conspicuous of them. We will begin with that family of bricks of which the London stock brick is the type. It has been said these are clamp burnt, and almost all the internal brickwork--and not a little of the external--of the metropolis is of stock brickwork. A good London stock brick is an excellent brick for general purposes, but cannot be called beautiful.

Considering the vast quantity of brickwork done in the metropolis, it is a matter for congratulation that such sound materials as good stock bricks, stone lime, and Thames sand are so easily procurable, and can be had at a price that puts them within the reach of all respectable builders. When a clamp has been burnt its contents are found to have been unequally fired, and are part of them underburnt, part well burnt, part overburnt. They are sorted accordingly into shuffs, grizzles, stocks of two or three qualities, shippers, and burrs. Several sorts of malm stocks, which are superior in color and texture, are made, and are used for facing bricks and for cutting; and what are called paviors, which are dark and strong bricks, are also made. The London stock is erroneously, but usually, described as gray. It is really of a pie crust yellow of various tones. Sometimes it is the same color when cut, but the hardest stocks are of a dark, dirty purple or brown, or sometimes nearly black inside. A stock brick is rarely quite square or quite true; its surface is often disfigured by black specks and small pits, and a stack of them often looks uninviting; yet a skillful bricklayer, by throwing out the worst, by placing those of bad colors or much out of shape in the heart of the wall, and by bringing to the front the best end or side of those bricks which form part of the face, can always make the bricks in his work look far better than in the stack. Another important group is the group of Suffolk and Norfolk bricks, red and white. These are very largely employed as facing bricks and for arches and cut mouldings.

Moulded bricks are also to a large extent made of the same material. These bricks are brought to London in large quantities. They have a sanded face, are mostly square, true, and of uniform color, but they are usually porous, soft, and absorbent. Still, they are in great demand as facing bricks, and the moulded bricks enable the architect to produce many architectural effects at a moderate outlay. These fields furnish many sorts of bricks, which are called rubbers, and which are employed (as malm stocks also are) for arches of the more elaborate sort, where each brick is cut to its shape and rubbed true, and for mouldings, and even sometimes for carving.

Mouldings that are formed by cutting the bricks can be got more perfectly true than when moulded bricks are used; but the expense is greater, and when it is done the material is less durable, for the softer sorts of brick are naturally used for cutting, and the moulded face is less sound than the original burnt face of any brick. Red bricks are to some extent made in fields within easy reach of London; but the best come from some distance. Red Suffolk bricks have been alluded to. There is a considerable importation of red Fareham bricks, brought all the way from the vicinity of Portsmouth; these are good both in quality and color. Good red bricks are also now made at Ascot, and are being used to a considerable extent in the metropolis. A strawberry-colored brick from Luton has been extensively used at Hampstead. It is hard, and of a color which contrasts well with stone, but not very pleasing used alone. Glazed bricks of all colors are obtainable. They are usually very hard and square, and the use of them where an impervious glazed face is required, as, for example, in a good stable, is better than the employment of glazed tiles, in the employment of which there is always a possibility of part of the lining becoming loose or falling off. There is a difficulty in obtaining a large quantity (of some colors, at least) exactly uniform in tint. Bricks with a very hard face, but not glazed, are obtainable. What is called a washing brick is now made in various colors, adapted for the lining of interiors, and there are hard bricks of a very pale straw color, known as Beart's patent bricks, made, I believe, of gault clay, which were some years ago bought up by the Great Northern Railway in large numbers. These bricks have the peculiarity of being pierced with holes about ½ in. in diameter, passing quite through the brick, and they are extremely hard, partly because these holes permit the hot air and smoke in the kiln to approach very near to the interior of the brick. I am of opinion that the glazed or dull qualities of hard bricks might with great advantage be often introduced into London streets. What we want is something that will wash. The rough surface of stocks or Suffolk facing bricks catches the black in the London atmosphere and gradually gets dark and dull. A perfectly hard face is washed clean by every shower. A good many years ago I built a warehouse with stock bricks, and formed the arches, strings, etc., of bricks with a very hard face, and, as I expected, the effect of time has been to make these features stand out far better than when they were fresh; in fact, the only question is whether they have not now become too conspicuous. To return to the bricks in the London market: we have firebricks made of fireclay, and almost vitrified and capable of standing intense heat. These are used for lining furnaces, ovens, flues, etc.

Then we have almost, if not quite, as refractory a material in Staffordshire blue bricks, used--in various forms--for paving channels, jambs of archways, etc. There are also small bricks called clinkers, chiefly used for stable paving. Dutch clinkers, formerly imported largely from Holland, were small, rough bricks, laid on edge, and affording a good foothold for the horse. Adamantine clinkers, made of gault clay, are much used; they must have chamfered edges, otherwise they make too smooth a floor for a stable. Many other varieties are obtainable in London, and are more or less used, but these are the most prominent. In many parts of England special varieties of brick are to be found, and every here and there one falls upon a good brickmaker who is able to produce good moulded or embossed or ornamental bricks, such as those which have been supplied to me years ago by Mr. Gunton, and more recently by Mr. Brown, both of Norwich, or by Mr. Cooper, of Maidenhead.

It is of importance to those whose business it is to look after or engage in building operations, that they should early learn what to look out for in each material. Of course, a man only becomes a judge of bricks, or timber, or stone by experience; but he is far better able to take the benefit of experience when it comes to him if he knows from the first to what points to direct attention. Wherefore I make no apology for trying to put before you the points of a good brick, and in doing so I shall partly quote from a memorandum published now a good many years ago by the Manchester Society of Architects.

A good brick is uniform in size; standard, 9 by 4½ by 2½ in.; weight about 7 lb. each = 110 lb. per foot cube; is rectangular, true faced, but only one end and one side need be smooth; has no print sinking on either face, but a hollow on one or both beds. When saturated with water, a brick should not absorb more than 20 per cent, of its own weight of water, should absorb it reluctantly, and part with it freely at ordinary temperatures. It should be uniformly burnt, should be sound, free from cracks, flaws, stones, lumps of any kind, but especially lumps of lime, should be of a good color for its sort (whether red, yellow, or white), should have a metallic clang when two bricks are struck together; when broken should be sound right through, should be tough and pasty in texture, not granular, and should require repeated blows to break it, rather than one hard blow (such bricks will withstand cartage and handling best). So much for bricks. To make brickwork, however, another ingredient is required--namely, mortar or cement.

All mortars and, in fact, all the cementing materials used (except bituminous ones) in bricklaying have lime as their base, and depend upon the setting quality of quicklime, which has to be mixed with sand or some suitable substitute for it, to make mortars. Limes and cements are far too wide a subject to be dealt with as part of an evening's lecture on another topic, and no doubt they will hereafter form the subject of a lecture or lectures. To-night I propose only to remind you that there are such substances as these, and that they possess certain qualities and are obtainable and available for the bricklayer's purposes, without attempting an investigation into the chemistry of cements, or their manufacture, etc. Ordinarily, brickwork may be divided into brickwork in mortar and in cement; but there are many qualities of mortar and several sorts of cement. Mortar made with what are called fat or rich limes--that is to say, nearly pure lime, such as is got by calcining marble or pure chalk--sets slowly, with difficulty, and is rarely tenacious. Burnt clay or brick reduced to powder improves the setting of such lime, especially if the two materials be calcined together; so will an admixture of cement. Mortar made with what is known as slightly hydraulic lime, that is to say, lime containing a small proportion of clay, such as the gray stone lime of Dorking, Merstham, and that neighborhood, sets well, and is tenacious and strong. Mortar made with hydraulic lime, that is to say, lime with a considerable admixture of clay, such as the lias lime, sets under water or in contact with wet earth. It is best to use this lime ground to powder, and not to mix so much sand with it as is used with stone lime. A sort of mortar called selenitic mortar, the invention of the late General Scott, has been made use of in many of the buildings of the School Board for London, and was first employed on a large scale in the erection of the Albert Hall. The peculiarity consists in the addition of a small dose of plaster of Paris (sulphate of lime) very carefully introduced and intimately mixed. The result is that the mortar so made sets rapidly, and is very hard.

It is claimed that a larger proportion of sand can be used with selenitic lime than with ordinary, thus counterbalancing the extra expense occasioned by royalty under the patent and special care in mixing. When a limestone contains 20 to 40 per cent, of clay, it becomes what is called a cement, and its behavior is different from that of limestones with less clay. Ordinary limestones are, as you know, calcined in a kiln. The material which comes from the kiln is called quicklime, and, on being dosed with water, it slakes, and crumbles to powder, and in the state of slaked lime is mixed up with mortar. Cement stones are also calcined; but the resulting material will not fall to pieces or slake under water. It must be ground very fine, and when moistened sets rapidly, and as well under water as in air, and becomes very hard and is very tenacious. Brickwork in mortar will always settle and compress to some extent. Not so brickwork in cement, which occasionally expands, but is never to be compressed. This quality and the rapid setting, tenacity, and strength of brickwork in cement make it a most valuable material to use in those buildings or parts of a building where great steadiness and strength are wanted, and in sewage and dock work, where there is water to contend with. A good many cements made from natural stones used to be employed, such as Medina, Harwich, Atkinson's, or Roman cement. The last named is the only one which is now much employed, except locally. It has the quality of setting with exceptional rapidity, and is on that account sometimes the best material to employ; but for almost every purpose the artificial compound known as Portland cement is preferable.