EXCERPTS FROM:


BRICKWORK IN ITALY


AMERICAN FACE BRICK ASSOCIATION (1925)

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PREFACE
BRICK IN CONSTRUCTION
WALLS ARCHES VAULTS
BRICK IN DECORATION
PART 2: BRICK IN THE MIDDLE AGES

PART 1: BRICK IN ROMAN ANTIQUITY

by Prof. Ing. Carlo Roccatelli

*** MANUFACTURE AND SIZE ***

(Pages: 1-5)

T HE very serious deficiencies in the study of ancient art and technique, and still more the prejudices and false premises which have guided scholars up to the present, do not permit of obtaining clear and reliable information regarding brick manufacture in antiquity. The numerous, though unfortunately ill-preserved, remains of Etruscan, Latin, and Campanian constructions prove that brick and especially architectural terra cotta were in use before the IV century B. C.


The discovery of ancient dies in preparing the ornamental terra cotta of ancient Italic temples (di Vignale, dei Sassi Caduti, etc.), and the examination of the material itself, lead us to believe that bricks, tiles, and terra cotta were made by means of moulds and dies, and dried and burned by a process differing little from that of today, leaving out of consideration, of course, the use of modern machinery and kilns.

An important observation made by Della Seta, and easily verified by direct examination of the materials, is that, as far back as these times as well as later throughout the entire roman period, pozzolana (1)was used with clays as a reducing material for burned bricks and, according to Marcus Vitruvius Pollio, chopped straw for bonding in sun-baked bricks.


Vitruvius, who flourished in the days of Julius Ceasar and Octavianus (Augustus, to whom he dedicated his work, De Architetcura, does not give us much information concerning the manufacture of brick. He says only that there were in uselateres , that is, sun-baked bricks, and lateres cocti or testacei which were burned. He does not give us, however, a list of the various types of bricks then in use, and also their dimensions. They are so-called Greek Lydium, one by one and half feet (2); the Tetradoron, a brick (3) four palms square; and the Pentadoron, five palms square. It is evident from these names that the practice in brickmaking among the Romans was at first greatly influenced by the Greeks, although their own practical genius subsequently introduced many other sizes and forms.


Aside from the three types of brick just mentioned, Vitruvius further speaks of half-bricks in a passage much discussed by scholars up to the present day, since it may be inferred that the bricks were cut in halves, either along a line parallel to one side, thus obtaining two rectangular bricks, or along a diagonal line, giving two triangular bricks. The latter might easily be inferred from the immense quantities of triangular brick found in Roman construction. But the question of Vitruvius' meaning may be considered as solved when we call to mind that the use of triangular brick first appeared in Rome with the constructions of Claudius (41-54 A. D.) and hence at a period later than Vitruvius. Besides, Ortiz y Sanz observes that if Vitruvius had had in mind triangular bricks, he would have called them lateres trigones and not semilateres. In addition to the above mentioned bricks, Vitruvius refers also to the laterculi besales, bricks about eight inches square, or two thirds of a foot. But, aside from the data furnished by Vitruvius, we may be sure that the brick dimensions were variously modified throughout the long centuries of Roman civilization.


Beside brick, very naturally, tiles were manufactured for roofing, both curved and flat, the dimensions of which varied from 38-77 cm. [15-30 in.] in length and from 28-56 cm. [11-22 in.] in breadth. Especially in the I and II centuries A. D., not infrequently, brick were used which had been originally manufactured as flat roof tiles and afterwards transformed into bricks by cutting off their edges and smoothing them on slabs of stone.


The use of tegulae fractae [broken tiles] is supposed to have originated from the convenience of utilizing the material gathered from the ruins of great fires from which Rome suffered not a little (4).


Form the time of Claudius, and during the following centuries, triangular bricks were much used. They were obtained by cutting the above-mentioned baterculi besales, before burning, along a diagonal line, thus producing bricks approximately 20 x 20 x 30 cm. [7.9 x 11.8 in.] and then bisecting these last, giving a size of about 15 x 15 x 20 cm. [5.9 x 7.9 in.]. On the dimensions and uses of bricks in antiquity, we have today much information and detail classification; but attempts to give this a strictly chronological value must be regarded with great reserve.


An interesting peculiarity found in Roman brick and tile, from the middle of the I century on, and which undoubtedly originated in the Orient, is the seal or trade-marks impressed upon them. These marks, besides possessing a very great chronological and topographical interest, often reveal the source from which the clay was taken, and the place and date of manufacture, etc (5). They were of various forms - circular, semi-circular, crescent-shaped, or rectangular and testify by their great variety how numerous the brick factories must have been.


*** BRICK IN CONSTRUCTION ***

(Pages: 5-8)

The use of brick construction in Roman antiquity, contrary to what a superficial observer might believe, was very widespread, indeed one might say almost general. Passing by the well known, venerable monuments of Roman art, the notable character of which demanded in their exterior forms the use of stones and marble, let us seek rather to obtain a close view of the familiar life of Rome by turning our attention to those elements which, up to our day, have been so much neglected as to seem foreign to the classical world as known to us. In fact, by observing the humbler class of buildings, those in which the activities of every-day life were carried on, those quarters of the ancient city inhabited by the middle class, by merchants and workmen with their houses, shops, and taverns, where in short pulsed the real life of antiquity, we experience a complete transformation of the ideas we had formed of ancient architecture by our observation of stately temples and sumptuous public edifices.


The excavation at Ostia, even more then those at the less commercial and more tranquil Pompeii, shed great light upon the subject. We see in fact how general was the use of brick and how it afforded many solutions in construction and admirable decorative effects, while the use of cut stone was, as today, only an exception.


And if the evidence of ancient constructions themselves is not sufficient, Vitruvius reminds us of their value, by praising the structures of brick as worth of being the dwellings of kings. While burned brick were used in buildings within the city of Rome, he tells us why sun-baked brick should not be used and then gives rules for their use in construction outside the city. Dion Cassius informs us of the disastrous effects of the inundations of the Tiber upon many buildings of sun-baked brick, and finally Suetonius relates how Augustus was able to boast that he had received a Rome of brick but had left it one of marble.


Going back to the origins, we find, as one of the very first examples of brick construction, the Etruscan wall of Arezzo, mentioned by Vitruvius (in Italia Arretio vetustum egregie factum murum), built of burned brick with the facing so well executed as to cause Caporali of Perugia to write in 1536, nearly two thousand years after its construction: " Arezzo possess a wall of brick so excellently worked by hammer and laid that one can hardly see the mortar joints between them; more-over the brick are so well burned that the color is absolutely uniform." All this proves, at least indirectly, how widespread was the use of brick before the days of the Empire, and suggests how important had been both Greek and Tuscan influence.

*** WALLS ***

(Pages: 8-11)

Without going into a too minute chronological analysis, let us examine the use of brick in the various types of wall structure. In the construction of bearing walls, the Romans certainly did not have a uniform type either at a given period or in a given locality.

If up to the close of the I century B. C. Hellenistic and Etruscan tradition led to the frequent addition of wall construction in squared stones, nevertheless, the peculiar methods adopted by the building crafts soon caused the widespread use of walls built of a conglomerate enclosed between facings of other material, a type which became characteristic of Roman construction.


The great thickness of these walls made possible the rapid execution of the work and a marked economy. While the master masons, with care and skill, built the exterior surfaces of brick so as to form a sort of encasement, the common laborers carried on the work of filling in the caementum, a conglomerate formed of successive courses of mortar and rough unshaped stones which were tamped down as the work progressed (6).


This type of construction, however widespread its use, is not to be regarded as the only one known. In fact, there are not wanting examples of walls, of no thickness, built entirely of brick; and walls of mixed masonry, as well, consisting of brick and dressed stone.


The remains of pre-Augustan constructions, unfortunately not very noteworthy, are the first examples of the caementum wall construction. At first, we see appear the so-called stuctura testacea, a wall faced on both sides with broken tiles, smoothed on the outer edge after chipping off the falanges, and filled in with caementum between the two facing, without transverse brick bonding courses. The bonding of the interior nucleus to the exterior brick facing was entrusted to the good quality of the mortar and to the rough irregular inner surface of the broken brick or tile. We have example of this type of construction in the tomb of the Platorini of the Republican period, reconstructed in the National Museum at Rome. The borders of opening, and angles of walls, however, were built entirely of brick.


Under Tiberius (14-37 A. D.) this construction appeared in an improved form; the two faces of the wall were bonded together, depending on the building or the builder, all the way from every fifth up to every seventeen course by large square bricks, the tetradoron or pentadoron. Examples of this work may be found at Rome in the Domus Tiberiana on the Palatine and the walls of the Castro Pretorio in which latter we have also a first example, although a very simple one, of face brickwork with decorative cornices, loopholes, and battlements.


The external facing, however, was much more commonly built of triangular bricks with the apex laid inward, thus making an excellent bond with the internal caementum nucleus, which was then crossed at the regular intervals by horizontal courses of large bonding bricks or tiles through the entire thickness of the wall. The use of these triangular bricks, beginning the times of Claudius as already noted, spread widely; for, beside offering a better bond with the nucleus and a more uniform appearance on the wall face, it obviously afforded greater economy of material.


Another type of wall structure was the opus reticulatum (7) in which, however, brick played only a small part. Here the facing on the caementum nucleus was made up of little cubical blocks of tufo laid with the sides at 45o to the perpendicular. At intervals there were framing square of brick, and brick projections, corners, architraves, arches, and the like. This type of construction was in use from the time of Sulla (138-78 B. C.) to that of Hadrian (117-138 A. D.) after which it quickly disappeared. Although this type of wall was almost always covered with architectural decoration in cut stone or stucco, it presented nevertheless when exposed, quite a pleasing and decorative appearance. Many very beautiful examples of it are several tombs of the time of Claudius at Ostia.


Passing over other related types of wall, which have no direct bearing on our subject, we finally mention however the opus mixtum. This form of construction is composed either of alternate courses of brick and squared stone, a type which appeared after Hadrian and developed very greatly in the age of Constantine, or of brick and cobble stones laid herringbone fashion, opus spicatum, a type quite common in Northen Italy.

*** ARCHES ***

(Pages: 12-13)

Not entering into a discussion of the form of arches, almost always semi-circular or segmental, we note first of all that their construction was directly connected with that of the wall and took on rather an external organic expression. Brick arches were generally built of bipedales, the larger tile-like brick two feet square, and show more or less careful workmanship. At times, in order to obtain perfect execution and to make the mortar joints uniformly thin throughout the entire face of the arch, cuneiform or wedge-shape bricks were used, as in the Colosseum. In arches of considerable size or subject to heavy weight, it was customary to adopt the double concentric type of arch which permitted a better and more regular adjustment of the wall mass. Characteristic example of these arches are found in the Pantheon, and in the Basilica of Maxentius, and elsewhere. More often arches were of a mixed construction, brick upon the faces and concrete in the interior. Then almost always the nucleus of the concrete had at intervals bipedales or sesquipedales in horizontal courses set radially, which bonded together the two external arch faces; or perhaps , in addition, there were other arches in the interior of the nucleus, always bonded together by large tiles, thus forming a network of brick compartments into which the caementum was placed. In this manner interior forces were distributed and the curve of pressure fixed. One of the first examples of this type of construction is that of the Claudian arches on the Caelian Hill at Rome. Another use of brick may be mentioned as a typical Roman architectural motive and that is string courses or architraves combined with semi-circular relieving arches, and also relieving arches incorporated in the wall structure, either to concentrate the stresses at determined points of the foundations or to obtain a better and more uniform adjustment of the wall mass. Of these we have any number of examples.

*** VAULTS ***

(Pages: 13-23)

The vaults , a typical element of Roman architecture, of which it forms the principal characteristic, was always the object of assiduous study on the part of the ancient builders. In it we see brick assume a great and special importance because of its varied and ingenious applications. The typical construction of the Roman vault was of the nature of the caementum already described, in which suited admirably the organization of Roman labor and in which we may easily recognize the archetype of our modern concrete construction.


To the unquestionable advantages of this system - economy and rapidity of construction - were opposed the inconveniences which arose from the necessity of using strong supports during construction and from the dangers due to the even the slightest settling of the foundation which would cause immediate and very serious injury. However, builders strove constantly to eliminate these disadvantages, and the history of this construction offers numerous expedients devised for this purpose.


One of the most common of these aimed at the elimination of the complicated wooden centering which necessarily had to form a continuous and complete support, held up by very strong braces. It consisted of a vault or casing of brick laid flat, alternating from time to time with brick laid on edge, and bonded with quick-setting mortar so as to form a sort of template which, beside giving the form of vault, supported the layer of concrete with which it at once bonded.

The first example of the kind known, we have in the Colosseum. Later imposing examples are such as those in Hadrian's Villa near Tivoli, in the Baths of Caracalla, etc. Others of particular interest may be found in the houses at Ostia, which, were sometimes built of a double layer of brick as if to afford greater assurance of their resistance to the heavy weight of concrete put upon them.

An expedient devised to lighten the concrete mass of the vault and consequently to diminish the weight upon the piers was the insertion of terra cotta amphorae or wine jars, especially in the groins, sometimes set irregularly, as in the Stabian Baths at Pompeii, in the Villa dei Gordiani at Rome, etc.; at other times with a more definite constructive methods, as those at Pompeii, and especially later in the constructions of the III and IV centuries. To be historically correct, however, we must remember that the first use of earthenware jars in the interior of walls masses, although following different principles, was made at Aosta in the Augustan age.


Another improvement, in connection with the use of brick in vaulting, introduced on constructive principles of a different nature, was that of subdividing vaults and cupolas into bearing arches of bricks with intermediate fillings. The bearing skeleton was composed of brick ribs set along the transverse lines of the vault, along the diagonals of the crossing, or along the meridians of the cupola, thus directing the thrusts and concentrating them at the more resistant points of the piers.


The dispositions of these ribs in vaults was extremely varied and improved gradually with the progress of the static concept in construction. From simple brick semi-circles in barreled vaults and from rudimentary groinings, of which one of the first examples is found in the Colosseum, we see the gradual development of this principle in the diagonal ribs of intersecting vaults with ingenious disposition of the bricks as, for example, in the Arch of Janus Quadrifons, in the Palace of Septimius Severus on the Palatine, in the Baths of Diocletian, etc. At times these ribs projects, as in Villa dei Sette Bassi, as if to anticipate the classical type of crossing in Lombard architecture, until they develop into the ribs of cupolas as in the Sepulchre of the Calventii, in the Temple of Portunno at Porto, etc. These groinigs, in which we may perhaps see the germ of that conception which found full development and perfect application in the marvelous cupolas of our Renaissance and successive epochs, had their stylistic expression in the coffering or paneling at the time when the cupola was introduced. At times these ribs do not mark the meridian of the cupola but are interlaced as in the apse of the Temple of Venus and Roma at Rome and as appears from some drawings of Renaissance artists.


Finally, we may note among many others, two particular use of brick. Pavements which were generally made either of large flat tiles or of very small bricks set on edge in herringbone fashion, and the wall surfaces of baths (laconicum and calidarium) were constructed of one-celled hollow bricks, generally 8 X 13 X 33 cm. [3.2 x 5 x 13 in.] in size, which afforded passage for the circulation of smoke and hot air. This ingenious and widespread system of heating which is found at Pompeii was first extensively applied in Hadrian's Villa near Tivoli and later in the Baths of Caracalla and of Diocletian at Rome.


*** BRICK IN DECORATION ***

(Pages: 23-26)

As already indicated , brick was used generally from the most ancient times, not only in construction but also for exterior decoration, especially in buildings of the modest architectural type where the real life of the common people and of the middle classes was unfolded in all its manifestations. Unfortunately, there exist only rare and inadequate remains of these buildings which, just because they lacked public or monumental character, were not only more or less neglected but suffered greatly during frequent periods of reconstruction, as well as form the trying vicissitudes of the centuries, and hence more readily despaired on the course of time.


However, the remains of widely scattered tombs in the environs of Rome, the edifices brought to light at Pompeii and preserved (at least in their essential parts) trough the terrible caprices of nature, and still more the excavations at Ostia, prove to us that the brick and terra cotta were widely used for the purposes of decoration. In fact, along with the monumental architecture of imposing temples and sumptuous public edifices, covered with rich decorations in stone and marble, we see developed a real architecture in brick and terra cotta. In houses, shops, taverns, and sepulchral edifices, brick was used for wall surfaces artistically done, for simple and refined cornices, for panels, and the like. And often with special bricks, cut in ovoli, dentils, palm-leaves, scales, etc., cleverly adapted, there were formed brackets, elaborate cornices, Ionic, Corinthian, and Composite capitals, and in general all the motives and varied compositions of classical architecture which showed that the use of brick held no secret for those accomplished builders of ancient Rome.


Sometimes, alongside of this richer decoration, we see walls adorned with simple panelings, cornices, etc., which give them a very pleasing relief and a harmonious aspect. Often the effect of polychromy was cleverly exploited chiefly by the use of yellow, red, and brown bricks, which were at times intermingled without any definite aim, as in the I>Anfiteatro Castrense. More frequently, however, by following an exact decorative method, the color scheme was attained by building the projections of the wall, generally the architectural orders, of light-colored bricks and the background of darker ones or vice versa. Often the frieze stood out, because of the yellow color bricks, in contrast with the reddish browns of the architrave and cornice. Quite frequent also was the use of decorative terra cotta, moulded with rare skill and exquisite artistic sense, which gave a peculiar beauty and vivacity to the entire architectural organism.


Speaking generally, and judging from the remains, it may be said that the use of burned brick began to spread rapidly towards the close of the Republic. At that time, and generally throughout the period of the first emperors, brickwork was characterized by regularity, and great care in execution; the mortar joints were very thin, so thin that, especially on the face wall, they did not exceed two or three millimeters in thickness [1/12 or 1/9 in.]; the bricks were of excellent clay and manufacture, well burned, and very hard.


In the I and II centuries, there began at first to appear various defects in the brickwork which later became gradually more marked. The mortar joints increased in thickness as to exceed more than three centimeters [1.2 or 1.6 in.]; the courses were less regular and in the end came to be laid with bricks of all dimensions. Not infrequently, there were used, during the last years of the Empire, bricks taken from ruins, and construction in general betrayed a very careless execution. The bricks to begin with were of a lower grade and coarser texture, made of poorly pugged clay, and the workmanship in laying showed signs of deterioration.


Decoration followed the general course of Roman art. Sober, elegant, and of the purest lines in the days of the Republic and the first years of the Empire, it became richer and richer and invaded every exposed surface on the wall up to the point of becoming exuberant, though it preserved great correctness of form. Later, with the decline of art, we find it becoming commonplace, poor, misshapen, and showing clearly in what a short period of time that art declined which has left to the world so many wonderful monuments.

SEE ALSO:
Roman Architecture
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(1) Pozzolana is a siliceous volcanic dust containing ferric oxide, alum, chalk, and magnesia, deriving its name from Pozzuoli, near Naples, where it was first utilized; afterwards found in great beds on the Roman Campagna. Vitruvius gives an interestingly curious account of it in II, 6 of his treatise. Mixed with lime and water it makes a strong, enduring cement. [Ed.]
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(2) The Roman foot usually given as 29.6 cm. Or 11.6 inches. The Lydium according to Vitruvius, was commonly used by Romans. The Greeks used the Pentadoron for public and the Tetradoron for private buildings. [Ed.]
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(3) Rivoira gives the dimensions of the Pentadoron as one and a quarter feet, the foot taken as 30.9 cm. [12.17 in.]. This makes the " palm" 7.7 cm. [3.03 in.] and consequently the Tetradoron 30.9 in. or a fraction more than the Roman foot as previously given. Vitruvius does not indicate the thickness of the brick but Rivoira refers to a Pentadoron used at ancient Medma in the Campagna that measured in thickness 9 cm. Or 3.54 in. He also refers to Roman brick one foot long, a half foot wide, and a quarter foot thick as surmised by certain writers on the subject (Architectura Romana p.21). [Ed.]
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(4) Although kiln burnt brick at Rome began to be made in the Sullan period (138-78 B. C.) they did not gain wide and exclusive use until the days of the early Emperors. But though up to this time vast quantities of sun-baked or adobe brick were used for building, the roof tiles were necessarily kiln burned to endure the weather, in consequence of which floods or conflagrations left them still usable as building material. Vitruvius made the test of well burned brick, their use on a roof where they are "exposed to bad weather and time" (Book II, Cap. VIII, 19). In new of their durability it natural that roof tile should be utilized in constructions, for the entire surface of the wall, instead of the adobe brick. It was also natural that, aside from safety in drying and burning, the thinness of the tiles used for facing walls should establish a practice for the subsequent manufacture of the long thin Roman brick. Perhaps it was the structural use of the salvaged flat tile that led to the manufacture of the large standardize square brick known as sesquipedales (45 x 45 cm., a foot and a half) and bipedales (60 x 60 cm., two feet), the latter used extensively for bonding the wall and for arches. [Ed.]
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(5) M. Ch. Descemet ----- Inscriptions Dolares Latines, Paris 1880 ----- shows brick stamps with consular dates from 76 B. C. to as late as 554 A. D. , although nearly half of them belong to Hadrian's time. Marini's list, contains 5000 inscriptions and yet is not exhaustive. This practice was found in Italy outside of Rome as early as 75 B. C. but not in Rome itself before the days of Trajan. These stamps are very diverse and variously indicate: the owner of the clay pit; the factory where made, perhaps its owner; the date; the merchant that sold them; the destination; the construction served; or a claim of quality. Sometimes the center of the stamp bore a head of Mercury, an ox skull, the figure of an animal, a bird, an insect, or a palm leaf. See Dennie, Rome of Today and Yesterday, Putnam's , New York, 1910, p. 281 ff. [Ed.]
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(6) This opus caementum so called, was rough work of broken stones, pieces of brick and tile, and later even fragments of marble, laid more or less irregularly in a plentiful supply of pozzolana mortar. Vitruvius, who did not know its complete development, condemned its use in his day, as compared with the sounder Greek practice (Book II, Cap. VIII, 7). It is not difficult to conjure that the practical Roman builders, recognizing the durable solidity of the caementum work, soon learned to economize both in material and in time by saving the stone for the outer surface of podium or wall which in the mass could be done more quickly and cheaply in the caementum work, and done enduringly, in spite of the Vitruvian dictum. In a sense, the extensive pozzolana beds of the Roman Campagna made Imperial Rome possible. This opus caementum, bonded through its thickness and protected at angles and around openings by brick, needed surfacing or a cortina (curtain) either for appearance or for a better surface to take plaster. Hence marble, stone, small tufo blocks (in case of incertum or reticulatum work) or, most extensively of all, brick were used for facing. While the stone facing was sometimes plastered, it was in the main to the tufo and brick surface that stucco was applied, though many examples of fine brickwork are found which the original builders meant to be exposed because of its finished beauty. [Ed.]
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(7) This reticulatum manner doubtless was a development, on aesthetic grounds, of the opus incertum, irregular work (or insertum inserted work), of the late Republic, in which the small tufo pieces were introduced irregularly after the fashion of rubble work. The latter, Vitruvius regarded more durable than the reticulatum, though not as attractive (Book II, Cap. VIII, 1). [Ed.]
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