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Pottery in Archaeology

Published in

· 14 Dec 2022

Pottery constitutes the most abundant class of material routinely found in the course of archaeological excavations; it is precisely this abundance, combined with the constant variations to which it is subjected as a result of changing tastes and trends over the centuries, that gives it a fundamental archaeological value: that of a chronological indicator.

Through the study of the stratigraphic sequence we would in fact be able to establish only a relative chronological succession, which would not allow us to date in a strict, or absolute, sense the Stratigraphic Units that are the object of our study: only through the study of the pottery can we therefore make the leap from the simple analysis of the succession of stratigraphic units to the dating within a well-defined chronological span of the actions of which the Stratigraphic Units constitute the material trace.

In carrying out such a study, however, it will be necessary to distinguish the so-called "in-phase" material, that is, contemporary with the formation of the US, from the so-called "residual" material: in fact, only the former can be used for the dating of the US under examination, while the latter will constitute the evidence of UUSS, and therefore of actions, prior to the one under examination, disrupted and mixed as a result of subsequent interventions. In distinguishing these two groups of material, the study of the conformation of each fragment will also be able to help us: fragments characterized by sharp edges will be indicative of the so-called "primary layering," and thus of material contemporaneous with the formation of the US; rounded edges, on the other hand, will be indicative of "secondary layering," and thus of residual material, which cannot be used for dating purposes.

Thus, the training of a good archaeologist cannot disregard knowledge of ancient ceramic technology and the different types of production that occurred over time.

CLAY

Clay, the raw material for the manufacture of ceramic objects, is naturally found along riverbeds and in banks, exploited since the earliest times by means of quarries; it is a sedimentary rock, formed of clay minerals (such as kaolinite, used for porcelain) and non-clay minerals (such as silicates, calcite, ferric oxide, manganese oxide and other oxides in smaller percentages).

The characteristics of clay are:

plasticity, which determines its moldability
the reduction in volume during drying and firing
refractoriness after firing
the resistance to impact and thermal shock after firing

Given the extreme variety of naturally occurring clays, not all have the characteristics suitable for processing: clays that are too calcareous or sandy ("lean" clays) are not very plastic and require purification to be worked; similarly, clays that are too plastic ("fat" clays), which do not maintain the shape they are given, require the addition of degreasers such as quartz, chamotte (terracotta reduced to powder) and pozzolan, i.e., elements that can reduce the natural plasticity of the mineral and make it more easily moldable.

The use of degreasers then serves to give the pottery greater resistance, both to shocks and to changes in temperature: think of fire pottery (pans, casseroles, etc.), bricks (bricks), and large containers for foodstuffs (dolia).

FROM CLAY TO POT

A series of preliminary operations must be carried out before the shaping stage:

curing: consists of leaving the raw material in the open, so that the organic components can putrefy and the larger inclusions can be removed. II process increases the plasticity of the clay.
purification: the purpose, partially achieved through the curing process, is to rid the clay of foreign particles; to do this, communicating tanks are used, placed at different levels, in which the clay, transported by water, passes from tank to tank, gradually depositing the heavier particles on the bottom. II level of purification of the final product is directly proportional to the number of tanks; another system used was decantation in still water, with which the so-called "barbotine" was obtained, a highly purified and very sticky clay used for decorations and for "gluing" the accessory parts of the vase (handles, sockets and feet).

At this point, after assessing the possible need for degreasing agents, the clay, mixed with water, is ready to be worked.

There are mainly three modeling techniques:

--by hand: a system used for the oldest pottery, it is made with clay beads "mounted" on each other in a spiral pattern (colombina technique).

pottery modelled by hand

-by tome: system used in Italy widely from the late of the 8^th century BC, it consists of a pivot at the ends of which are mounted two discs, the upper, on which to work the pot and the lower, operated by means of the foot, to give the tool the rotary movement necessary for working the pot (turning).

pottery modelled by the tome

-Matrix working: clay is placed in molds for making complex shapes and decorations; very often matrix working can be used in conjunction with lathe working: the matrix is placed on the lathe and the clay is made to adhere to the wall of the matrix by the rotary motion of the lathe.

pottery modelled by using a mold

THE FINISHING AND DECORATION OF THE POTTERY

Decoration is usually done before the drying and firing stages and is mainly of three types:

relief decoration

applied: plastic forms are made with the use of molds and then affixed to the vase with "barbotine" which acts as a glue.
a matrix: both the body of the vase and the decoration are obtained through the same matrix, usually made of fired clay, engraved in negative.
a barbotine: the decoration is made with a syringe (similar to today's confectioner's syringe) filled with "barbotine". Only rather simple motifs such as plant or geometric decorations can be made.

imprinted/embossed decoration

impression: is made before drying the piece with small stencils (stamped decoration), a string or with the fingers themselves (digital impression).
engraving: is made before firing with a wheel engraved in negative (wheel decoration), with combs making bundles of parallel lines (comb decoration) or with simple awls.
scratching: made after firing, usually used to make inscriptions rather than decorations.

painted decoration: can be made with vitrified clay paints or with colors of plant origin.

After the modeling and possibly decoration stage, the objects had to dry completely in a cool, shady place.

Before firing, the vase may be coated with clay, which is more purified than that of the body of the vase, which takes on different colors with firing; depending on the composition of this "paint" we speak of:

ingabbiatura: this is done with clay that is more liquid than that used for the body of the vase. In firing they take on various colors depending on the chemical components of the clay used, with outcomes from bright red to cream to white.

Calcareous clays: white to cream
Clays rich in ferric oxide: tones of red and brown
Manganese oxide-rich clays: tones of yellowish and greenish

glazed clay varnish: paint composed of particularly purified clay that, when fired, "gresizes," takes on a coral red or black color and a "glassy" appearance. Sealed earthenware, black and red-figure vases, and black-glazed pottery are made with this technique.
glaze: this is a clay paint rich in silicates and lead oxide that allow it to vitrify during firing. The difference from vitrified clay paints is that the latter is an opaque and rather thick coating. Generally used in the production of medieval pottery, glazing was occasionally used as early as Roman production.

THE STAGES OF BAKING

Baking, regardless of the type of oven used, consists of two stages:

gradual raising of temperature

Firing

reaching and stabilizing the maximum temperature (between 800 and 1100°). At this stage, "gresization" or vitrification of the clay paint or glaze takes place.

Post-firing

gradual decrease in temperature until complete cooling. At this stage chemical changes continue within the clay at least until it reaches 200°.

Firing and post-firing can be carried out either in a reducing atmosphere or in an oxidizing atmosphere:

Reducing atmosphere: no air is circulated in the kiln and thus no oxygen is provided for the flame to burn; combustion, in order to continue, must take oxygen from the chemical compounds in the clay (oxides) that undergo oxidation-reduction (e.g., ferric oxide is transformed into ferrous oxide i.e., black magnetite).
Oxidizing atmosphere: air and thus oxygen circulates in the kiln.

By changing the atmosphere inside the furnaces, it is therefore possible to achieve different effects:

Reducing firing and oxidizing post-firing: in the firing phase the oxides are reduced and the phenolic oxide becomes ferrous oxide, giving the pot a dark or black color. Vitrified clay paints, at this stage, "gresify" by not subsequently changing their crystal lattice. At the post-firing stage, the return of oxygen causes everything that has not undergone "gresization" or vitrification to return to its original state. Black and red-figure ceramics and black paint are thus produced
Reducing and post-reducing firing: the lack of oxygen at all stages of firing produces brown or black pottery both on the surface and inside the vessel. Typical class made with this system is Etruscan bucchero.
Oxidizing firing and oxidizing post-firing: this is carried out only with irradiation kilns with the result that the vitrified clay glaze becomes coral red, like that of Italic terra sigillata.

POTTERY OVENS

The earliest system of firing, certainly used in protohistoric times and still, limited to some productions, in Etruscan times, is the pit kiln, consisting of a pit dug in the ground, inside which the pots are placed in contact with the fuel (composed not only of wood but also of dried fruit shells, capable of developing high temperatures). Finally, the oven was covered with earth.

an early oven, a pit kiln, consisting of a pit dug in the ground

Much more we know about the ovens used in Roman times:

Bare flame kiln: this is a kiln constructed of refractory clay with a lower combustion chamber and an upper firing chamber, divided by a grate on which the pots to be fired were stacked. Reducing-oxidizing firings are carried out in this type of kiln.

$a bare flame kiln constructed of refractory clay with a lower combustion chamber and an upper firing$

a bare flame kiln constructed of refractory clay with a lower combustion chamber and an upper firing chamber

Radiation kiln: In this type of kiln, the firing chamber and the combustion chamber are not communicating, and heat spreads, by radiation, inside the firing chamber through chimneys that pass through it. This kiln is used for an oxidizing type of firing-oxidizing.

a r adiation kiln, the heat spreads inside the firing chamber through chimneys

The temperature, at the beginning of the firing, is kept low and rises slowly so as to prevent the pots from warping or cracking.

THE ROMAN POTTERY

Black-glazed pottery

Fine tableware ceramic class characterized by a vitrified clay paint that turned black in firing, distributed over the surface of the object by dipping. Forms produced include plates, jugs, cups and other tableware-related objects. Decorations generally consisted of stamp impressions or comb carvings.

This is a widespread pottery produced throughout the Italic peninsula in the Republican period, specifically between the late 4^th and mid-1st centuries BC.

Black-glazed pottery

Earth Sealed Italica

Around the mid-1st century BCE the typical black-painted pottery was replaced by fine red-painted tableware. The earliest wares derived their shapes from black paint and were produced in the workshops of Arezzo around the middle of the 1st century BC. As early as 30 BCE, smooth Arezzo production was joined by matrix-decorated vessels made by craftsmen of Aegean-Eastern origin.

More problems there are in identifying the end of production, which certainly passes through a phase of internal change, with contraction of production centers and especially of the market. Aretine smooth production ceases around or immediately after the middle of the first century CE, but other Italic workshops continue the activity longer.

The sigillata of this latter phase show increasingly standardized forms and a reduced formal repertoire: conventionally they are called late Italic and include both plain and decorated matrix forms.

There are numerous data concerning the organization of production, due to the discovery and excavation of some kilns but especially at workshop stamps present on many specimens. A generally calcareous, very pure clay, which did not require lengthy purification processes or the addition of degreasing agents, was used to make the pottery.

The making of smooth forms involved the use of the potter's wheel (probably with the help of templates), which was equally used to mold within matrix decorated forms. Further decorations, either modeled by hand or obtained by mold (appliques) could be applied with liquid clay, barbotine, which was often used directly on the vase to compose small, simple decorative motifs. Painting was done by dipping the vase in a clay varnish that underwent a process of vitrification (grésage) during firing, becoming waterproof and shiny. The characteristic red color of the sigillata is due to the firing and post-firing, both of which were carried out in an oxidizing atmosphere within irradiation kilns in which there is no communication between the combustion chamber and the firing chamber.

The use of templates and dies allowed the mass production of identical vessels and required strict organization and precise division of the various stages of work. The personnel of these "manufactures" were probably specialized slaves, often of Aegean-Eastern origin, and freedmen. The number of slaves employed in production varied widely, with only a few workshops being able to afford more than twenty slaves, and only the largest purchasing skilled craftsmen to make dies and punches and having their own kilns and clay pits. We must therefore assume a system of association between the larger and smaller workshops, as evidenced by the passage of labor from one workshop to another, attested both by the stamps and by the presence of similar decorative repertoires in different workshops.

Competition among the various factories required the affixing of the maker's mark as a guarantee of product quality, but the stamp could also serve to distinguish the productions of different workshops that were often fired in a single kiln.

The great demand for sigillata on the market prompted the major workshops to soon open branches in Italic territory and beyond the Alps. The case of Ateius, an artisan from Arezzo, who expanded production by founding new workshops in Pisa and Lyon, is well known. Little do we know about the management of these branches, certainly the production technology and often the dies and punches came from the workshop, but we do not know whether they were branches dependent on the headquarters, or independent workshops, perhaps run by economically and legally emancipated freedmen.

Earth Sealed Italica

African Sealed Earth

African sealed earth is pottery made either by lathe or die. The orange color, either light or dark, bright or dull, is obtained by coating the pot with clay paint. Decorations, not very frequent, were made in applied relief or matrix.

The earliest pottery was produced from the early Flavian age onward in the Carthage region to meet local market demand, at the expense of tableware imports in Italic and Gallic sigillata. Initially, the formal and decorative repertoire, in imitation of Western sigillates, favored the spread of the pottery to African markets, and from the burrow of the 1870s AD, the elegance of these new productions determined the establishment of African sigillata in Mediterranean markets as well. The conquest of the Western and Eastern markets was favored not only by the standardization of products but above all by the socio-economic situation that Africa reached in the Middle Empire the abundant productivity of foodstuffs, especially oil, favored the spread of so-called companion wares, that is, pottery designed to occupy the interstices between amphorae in the holds of large cargo ships.

As early as the second half of the 1st century CE, African terra sigillata replaced Italic and South-Gallic productions, definitively conquering Western markets.

Between the late 3^rd and early 4^th centuries CE, workshops in northern Tunisia resumed production of fine tableware produced in matrix, characterized initially by sober mold decoration and, between the late 4th and first half of the 5^th centuries CE, by wheel, comb and barbotine decorations. The maximum diffusion of these products, not only pottery but also oil lamps, is to be found between the mid-4th and mid-5th centuries CE; already in the second half of the 5^th century CE the increase in the area of commercial diffusion came to a halt.

African Sealed Earth

Coinciding with the Vandal occupation of Proconsular Africa, between 422 and 533, the crisis in the production and marketing of the products began, a decline that could not be stopped by Justinian's reconquest of the North African regions (533/534 AD).

The end of production is to be placed in the 7^th century AD, coinciding with the Arab conquest of the region and in connection with the end of the great export of African oil.

African cooking pottery

This is fire pottery produced in Africa between the 1^st and early 5^th centuries CE and widely exported. Lids (with blackened rim), pots and pans (with ashy patina) are produced.

African cooking pottery

Thin-walled ceramics

The class basically collects drinking vessels (potori), among which glasses and cups can be distinguished; forms with a different function are rather rare.

Production is between the 2^nd century B.C.E. and the 2^nd century A.D. with scanty records, limited to very few forms, until the mid-3^rd century A.D.; production areas are located in the western Mediterranean basin, along the Rhine border of the empire and in Britain.

Specimens are often covered with varnish that makes imitation of metallic specimens more likely; it is absent in republican thin walls, with rare exceptions, appears rarely in the Augustan age, begins to be used frequently from the Tiberian age onward; it is generally reddish-orange, brown, or blackish-gray in color, also with metallic highlights.

Decorations can be divided into five basic types: sandblasted, incised, wheeled, barbotine, and depressed. Sandblasting is achieved by using an engobe of clay mixed with sand distributed with a brush or by immersion before firing; it can often be associated with high decorative types such as barbotine.

Engraving, often done with the aid of a comb or freehand, consists of highly stylized geometric or plant elements. Wheel decoration, (see incised decorations) sometimes associated with barbotine decoration, is particularly common on imperial-era forms.

Alla barbotine (see relief decoration). Depression decoration consisted of concave oval mirrors.

The earliest vases are made in the Etruscan-Latium area at the end of the first quarter of the 2^nd century B.C.; it is possible to assume the presence of manufactures in the Vesuvian area as well, although no kilns have been identified.

Thin-walled ceramics

In the late republican period other areas also begin to produce "thin-walled" pottery; near Syracuse and in northern Italy. The most active Adriatic producing centers are Aquileia (where kilns have been identified), and the Ravenna area.

The spread of Italic pottery to markets in the Mediterranean basin stimulated the emergence of provincial production. On the Iberian Peninsula, "thin-walled" productions have been identified in Cadiz in Betica, Mérida in Lusitania, and Ibiza and Majorca in the Balearic Islands.

Products from Betica, made from the second half of the first century B.C. onward, have a fairly wide export range that includes central Italy, southern Gaul, and West Africa.

Common-use pottery

This is a particularly difficult class of pottery to define, collecting everyday pottery suitable for the preparation of food (common fire pottery), its consumption and storage (common tableware and pantry pottery); these are local productions, rarely exported, that tend to privilege the functional aspect over the aesthetic one.

Common table and larder pottery, characterized by more purified pastes, includes jugs, bottles, amphorae, lids, cups, and plates, while in common fire pottery, which is poorly purified to better withstand thermal shocks, pots, pans, lids, and smoke burners are made.

Common tableware and pantry ceramics

Common tableware and pantry ceramics

Common fire pottery

Common fire pottery

Amphorae

These are transport containers used to market, especially by sea, various foodstuffs (wine, oil, fish sauces, dried fruit, honey), characterized by a generally elongated body, two vertical loops and a tip bottom, functional for stowage. Their study makes it possible to identify production and distribution centers and to reconstruct trade routes.

These containers are often accompanied by an epigraphic apparatus (vignettes) that is particularly useful for inferring information regarding the area of production of the amphora or its contents. During the republican age, and then to a greater extent in the imperial age, amphorae from all parts of the empire arrive in Rome carrying products typical of the provinces of origin: from Gaul came wines intended for mass consumption; from Spain, particularly from the region of Baetica, Rome imported oil and garum, that is, fermented fish sauces of various kinds intended for the seasoning of food; in the middle and late imperial age it was then Africa that replaced Baetica in satisfying Rome's needs with regard to oil and garum; from the East, on the other hand, came renowned wines, celebrated by ancient sources.

Wine: in late republican and imperial wine trade is characterized by the presence on the market of numerous qualities of wine, as well as derivatives of must processing. In addition to wine, nonalcoholic derivatives such as defrutum, sapa, and caroenum were produced and exported; these are "syrups" obtained by boiling and reducing must. II their use was quite varied; they could be used in cooking or as preservatives.
Oil: oil is the subject from the Augustan age of extraordinary distributions to the urban plebs. Such distributions became regular with Hadrian and free and daily, like grain, with Septimius Severus, who extended them to all of Italy. Most of the capital's supplies in the first century CE came from the Baetica and only later would Spanish oil be replaced by African oil.

Amphorae

Fish preserves: depending on the system of preparation, fish preserves, a particularly popular condiment in the Roman world, are defined differently:

Salsamenta: this is whole or barbed fish covered with salt.
Garum: a product of the decomposition of fish in a humid environment, it was prepared from pieces of fish, seafood, shrimp seasoned with salt and herbs. After steeping, the liquid was filtered and bottled.
Hallex: this is unfiltered garum that has not yet completed "maturation."

Lucerne

The earliest Italic-made oil lamps date from the mid-3^rd century B.C. Prior to this time, alternative lighting systems were favored, linked to the availability or wood and, to a lesser extent, beeswax. The only oil lamps in circulation between the 4^th and mid-3^rd centuries B.C.E. were imported or imitated Greco-Eastern products and had a diffusion limited to Magna Graecia and Sicily.

It was not until the second half of the 3^rd century B.C.E. that the first central-Italic types of production, made on the potter's wheel, emerged: in particular, the so-called "biconical Esquiline" type, a black-glazed oil-lamp, produced between about 250 and 50 B.C.E. by workshops in Latium and Campania and widely exported to the western Mediterranean, spreads widely in central-southern Italy.

The earliest matrix productions, datable from the second half of the 2^nd century B.C.E. onward, are made in Sicily and southern Italy and traded mostly locally; in the late 2^nd and early 1st centuries B.C.E., Latium workshops also began matrix production of oil lamps, often decorated and provided with a stamp that testify to the presence in Rome of a large number of workshops. New matrix oil lamps reached not only the coastal regions of the western Mediterranean but also inland regions, affecting the Rhone basin, central Gaul, and the Rhine border.

Between 50 and 20 B.C. the morphological repertoire changes considerably with the beginning of the production of oil lamps with beaks, whether round, angled, or ogival, decorated with volutes. These oil lamps, characteristic of the imperial age, are produced mainly in Latium and Campania and widely exported throughout the Mediterranean and at the borders of the Empire.

In the years following the middle of the first century CE there is a considerable change in the modes of production and in the organizational systems of the workshops: if up to now, as the numerous stamps found attest, production was entrusted to a multitude of small workshops, from the Claudian-Neronian period onward medium to large-scale factories begin to spring up, producing most of the stamped material, although this does not lead to the disappearance of the small workshops. In Cisalpine Gaul (especially the Modena area) large manufacturing complexes were formed producing oil lamps that were extremely simplified in decoration.

The ease of execution associated with the morphological simplicity of this oil lamp marks the transition to an "industrial" production requiring complex forms of workshop organization.

As early as the second half of the 2^nd century CE the provinces initiated their own massive production imitating Italic types until the 5^th-6^th centuries CE.

The restructuring of the productive organization also involved the central-Tyrrhenian area, which, between 80 and 120 CE, saw the concentration of production in a few large manufactories, at the expense of small-scale craftsmanship, which tended to disappear between the late-ﬂavia and Hadrianic periods. In Rome in this era the workshop of c. Oppius Restitutus dominates unchallenged, producing numerous oil lamps widely exported not only regionally. This situation is short-lived; already in the central decades of the Il century AD the balance between small and medium-sized enterprises is achieved and the number of small workshops increases again.

Lucerne

The shift to decidedly mass production also coincides with a technical and decorative decline in production that sees the rise of round-beak types characterized by simple, rather standardized decorations. This phenomenon is accompanied by a narrowing of the commercial scope for Italic-made oil lamps: while still in the mid-2^nd century CE the coastal regions of the western Mediterranean western Mediterranean continued to import Italic product, by the end of the century the central-Italic workshops were closing in on little more than a regional commercial dimension.

Glass

The production of glass containers dates back to very ancient times; the period that interests us most, however, is between the Hellenistic and imperial periods.

Beginning in the 3^rd century B.C., thanks to the expansion of trade, the opening of new markets and the development of the middle classes, glass production received a considerable boost that led to the multiplication of production centers. The use of the matrix technique, which had been sporadically practiced previously, favored the production of objects standardized in form, generally derived from the ceramic and metal morphological repertoire.

It was not until the late second and early first centuries B.C. that glass, previously considered a luxury commodity and characterized by extremely elaborate formal and decorative repertoires, became a more economically accessible and widespread commodity; this is in part due to the simplification of production systems probably implemented, at least initially, at workshops in the coastal Syrian-Palestinian area.

The Augustan age marks the time of influx to the West of master craftsmen working in the production centers of the Syro-Palestinian and Egyptian areas, through which Western artisans acquired, within a few decades, the technical heritage of glassmaking by blowing.

Among the earliest and most active Italic workshops should be counted those in Rome, which, with a series of innovations in the field of colors and with the simplification of production processes, made glass a true mass commodity.

Roman-era glass is obtained through two main techniques: matrix making and blowing.
The matrix technique allows the creation of numerous shapes and decorations.
The objects made can be monochrome or polychrome; between the princedoms of Augustus and Tiberius, glass vessels characterized by special decorations, such as millefiori glass, the lattice and ribbon technique, and the marbled effect, became established.

millefiori glass: with this technique, polychrome floral or geometric motifs were obtained by juxtaposing small cylinders of glass, which when heated formed the disc to be laid on the matrix. The small cylinders were obtained by juxtaposing glassy masses of different colors, which heated and pulled formed the filament to be cut.
lattice glass: the result of processing is a dense network of white or yellow color on a colorless background.
ribbon glass: the basic element consists of a rod formed from several colored elements that, arranged by parallel rows or quadrants and subsequently heated gives rise to a "banded" disk
marbled glass: by means of variously folded ribbons, the typical marbled appearance is given to the glass
gold-banded glass: the ribbons that make up the disc are rather wide, variously folded and interspersed with ribbons within which gold leaf has been inserted.

glasses

The taste for polychrome glass is slowly being replaced by new achievements in greenish-blue or even colorless colors that characterize the production of the late first century CE and later periods.

In the imperial period, shapes made by blowing are frequently found to be stamped: these are containers that can be dated mainly to the 1^st and 2^nd centuries CE.