Qantara Qantara

Stucco

In Islam

If one had to choose the defining material of Muslim culture, it would without a doubt be stucco. In contemporary history, plaster has been considered the poor relation of materials, probably due to its lack of applications in heavy-duty building work, its easy handling and the simple process it takes to transform it from rock mineral. But human dexterity, particularly that of Muslim artisans, helped to produce designs in stucco and numerous buildings decorated with that technique have survived for us to admire. To this day, Muslim culture continues to develop and create new designs that in the future may be described as works of art.

Obtaining stucco
The climatic conditions present in the Mediterranean during the Miocene Epoch (very hot and dry) promoted the emergence of evaporitic minerals such as gypsum. This raw material, which became accessible, was used as a building and decorating material. It became a resource very widely used by the cultures around the Mediterranean.
Stucco is both the rock (gypsum) in its natural state and the material obtained commercially. It is the latter which is the basis of most Muslim decorations, known as baked lime, bassanite or plaster of Paris. The variety of different phases and stucco allotropic states are due to the heat. Gypsum, when heated to temperatures between 120ºC and 1,000ºC, loses all or part of its crystallisation water and is then ready for use.

Uses of stucco, historical aspects
Some of the research known to date concerns the study and identification of different types of stucco. They show that its use emerged as a result of tests which aimed to change the appearance of the finish of sun-dried or baked clay used to cover mother-of-pearl, shell and lapis lazuli panels and reliefs in stone and alabaster. These applications emerged in Mesopotamia (western Iran) between the third and first millennium BC (Torres Balbas, 1955).
We know that the Egyptians used stucco from the Eighteenth Dynasty, apparently beginning in the Ptolemaic period (Mora and Philippot, 1984).
In a few monuments of the Greek Cyclades Islands, stucco tiles were found in the “West house” and the “Ladies’ House” (Marinatos, 1974) and tiles under the porch and in the megaron entrance (Wace, 1921), all dating from the Bronze Age.
In Roman times, plaster was used as secondary material in masonry, lime being the building material par excellence, as Vitruvius asserted in chapter III of the seventh book of his treatise De architectura in the first century BC.

Working and handling stucco
Any gypsum-based work undergoes changes during the mixing and goes through different phases. It is difficult to break down these phases but they affect the various aspects and finishes of stucco. The first stage, hydration, is the phenomenon that occurs on contact with water which transforms gypsum into hydrated calcium sulphate. The hardness of plaster at the end of the process depends on the volume of added water: the quantity required to hydrate a given mass of calcium sulphate has to be calculated beforehand. Setting begins when the stucco starts to lose its plasticity and the mixture first hardens. Finally, the crystallisation phase is a process that, during an exothermic reaction, involves the transformation of crystals in a new crystal network.
This simple process of the transformation of gypsum stone by mixing, its easy handling, and its high adaptability to a multitude of applications, as well as its strength and the speed with which it sets are among the factors that have made stucco a highly prized material. All these advantages explain how fast its use spread from the time of the early pieces found in the eastern territories dominated by the Sasanian Empire up to the Iberian Peninsula.
The work of chiselling stucco directly begins by the application of the paste on the walls. Once it is smoothed, the general lines of the composition are traced on it. The different patterns that are repeated along the wall are carefully cut and carved with a set of chisels, compasses and flat gouges. These simple metal tools are used to carve the decorative elements in a symmetrical fashion through rotation, translation and bending motions.
Mould work, where the resulting decoration can be chiselled, does not detract from the value of ornamental stucco. On the contrary, it allows for a great variety of motifs, which were fully exploited in the Muslim stucco decorations of the naturalist period. The casts brought about the evolution and specialisation of workshops. They had to develop a single rigid mould, use release agents and produce castings in individual sheets to be subsequently attached to the wall (Rubio et al., 1998).
The arrival of Muslims in Spain and the Nasrid period led to one of the high points of stucco decoration, the Alhambra in Granada, a beautiful monumental ensemble adorned with a wide variety of tiny patterns. Working with moulds allowed for highly detailed works and intricate designs. It reached a perfect succession of themes in two different depths, grouped on the lower level with interlacing and stylised plant arabesques (peppers, acorns, artichokes, jasmine, etc.) and on the upper level decorative stripes, geometric designs and inscriptions (cursive and Kufic).

Various uses
In manuals dealing with decorative arabesques, the terms of plaster, staff and stucco are often used to refer to the same decorations. While an organoleptic test confirms that this is the same material coming from the same raw material, the ways in which stucco is processed and prepared for use vary widely. Today, this test serves to distinguish the different historical periods and to date the works. The term stucco is used to define the vast majority of the decorations of Islamic culture up to the present. This material produces two main variants, whose colour is determined their components (white, yellow, pink, black). White stucco, made from very pure stones, must contain at least 66 per cent semi-hydrated matter. This unsifted white stucco is obtained from gypsum stones of the “Alabastro” or “Espejuelo” type. Black stucco, coarser, quite dark, is obtained by calcination of impure gypsum stones. In addition to ash and traces of combustion gases due to the rudimentary ovens it is heated in, it contains about 50 to 60 per cent semi-hydrated matter and comes with anhydrite.
The word staff usually refers to decorations or motifs produced in modern times. It is a material sieved into ovens where gases do not come into contact with it and which contains at least 80 per cent semi-hydrated matter. Its use dates from the industrialisation of production processes, which have resulted in a finer, whiter and purer material. It, too, can be obtained from gypsum stones of the “Alabastro” or “Espejuelo” type.
The word stucco is used to describe the inert material made from gypsum stone that has been subjected to a higher temperature, so it does not react with water. In order to use it, it is necessary to add a binder or mixtures of lime. This material, highly prized by the Romans for Byzantine stucco, was used everywhere as a primer for canvases; however, examples of this use in Islamic art are rare.
Despite its flexibility, high degree of insulation and elasticity, stucco has as a drawback: its very high solubility when it comes into contact with water.
Throughout history, its widespread use in construction had limits: it can be used outdoors in regions with limited rainfall and indoors in humid areas. However, stucco has been used outside by Muslims but until now, little was known about the protective layer that was used. Medieval masons knew the material and its reactions: their stucco decorations were always covered with a white layer of protection that is not normally found on staff or stucco. This primer was mainly composed of calcium sulphate and organic additives. Its application was necessary to increase the hardness of the stucco, to insulate it from external agents of corrosion, reduce porosity and soften the angles produced by chiselling the designs. All these conditions also facilitated polychromy. The application of the primer was very meticulous, the craftsman sometimes had to cover very deep levels of tiny details without removing any of the chiselled carvings. This technique of applying a waterproofing layer on top of a coat of rendering is a constant in the Islamic world, particularly in the region of Yemen. It uses a type of whitewash, “goss”, which consists of cooked plaster milk, slaked lime and egg white, which when applied to bathroom walls meant they could then be easily cleaned.

Muqarnas
Admired for its beauty and complexity, the muqarna is a major artistic contribution of the Muslim world. It combines, on the one hand, the geometry of angles and squares and is widely used in the designs of tiles based on mathematical calculations and, on the other hand, the physical laws of gravity applied to objects represented in three dimensions. This style of decoration was widely used on wood, but stucco offers the best illustration of this design thanks to its combination of flexibility strength, solidity, lightness and setting speed. The evolution of the handling of this material allowed the muqarna to be used on capitals, arches and even on steep areas such as roofs.
Inspired by the geological formations called stalactites, the first examples of muqarna appeared in spandrels where their octagonal shapes made the transition between square spaces and circular domes That shape appeared in the early tenth century and quickly spread from Turkestan to Andalusia although the debate continues as to whether its exact origins are in Persia or North Africa (Castéra, 1996). Few builders mastered the depth of mathematical knowledge needed to make them, but those who were able to became master workmen in the workshops. These accomplishments enabled them to cover spaces (regardless of whether they were circular, square or rectangular) by combining seven modules and adding a small observed, accepted and obligatory irregularity which made it possible to move from theoretical geometry to artisanal praxis. The master builders managed to raise the arches of muqarnas in various ways, to defy gravity, to revolutionise the theory of physics and to go beyond what had previously been achieved in vaulted spaces. There were already many muqarnas in the Mediterranean region, but it is the incursion of the Arabs in Spain that has left the most remarkable examples, such as the dome of the Hall of Abencerrajes, the Hall of Kings and the Hall of the Two Sisters at the Alhambra in Granada where there are over five thousand prisms.

R. R. D.

In Western Europe

Stucco, from the Italian, is a term that comes from Lombardy.  It was much used in antiquity as a substitute for stone. Its technique is well known to us through Book VII of De architectura by Vitruvius who describes the conditions for its making and its application. Following the fall of the Roman Empire, its utilisation was continued in Byzantium and, from the seventh century, was adopted by the Islamic world. Despite the paucity of documentation which might lead one to suppose that it fell into disuse in the West during the Middle Ages, this was not the case. It is associated with painting in the ornamentation of Christian sanctuaries, but, preserved more often than not as fragments, out of its original context and therefore has not received much attention from art historians until recently. Moreover, the critics are harsh concerning it, notably Viollet-le-Duc: “Stucco lent itself to this common type of decoration, and of all the artistic traditions of the Romans, this one must have lasted because of the ease afforded by the employment of such techniques. Build a wall out of rubble and when you have finished the edifice as best you can, hide the rough patches and botched places, with a rendering on which the engravers and sculptors can etch ornamentation borrowed from fabrics, furniture and oriental artefacts; this is obviously the approach that the naive architects of the Early Middle Ages willingly adopted.” Although it goes a bit too far, this observation is not without some truth and well describes the conditions which pertain to the use of rendering and stucco.

A technique and not a material

Stucco can be described as the process or technique by which a malleable substance can be worked to give the appearance of smooth stone. In Antiquity, it was made from a base of lime mixed with powdered marble; in the Middle Ages, it would be more often made from a base of plaster, sometimes mixed with lime. The material thus obtained, whether modelled or moulded at the beginning, was easily shaped before it hardened completely and was very strong once thoroughly dry. It therefore leant itself equally to producing flat surfaces, whether or not decorated with engravings or low relief, or to architectural forms such as mouldings, columns or capitals and even, more unusually, to statues in the round. The ease with which it could be worked  as well as its low cost explains its popularity in Antiquity and  from the Middle Ages up until the sventeenth century.

From Early Christian to the Carolingian periods

It was in places of worship, after Constantine's Edict of Milan in 313, that this type of decoration began to spread, often associated with mosaic work such as in the Orthodox Baptistery at Ravenna (Italy, circa 450). Used as simple wall decoration in the Euphrasian Basilica in Pore?, Croatia (formerly Parenzo, Istria) circa 650, preserved on the intrados of the great northern arches, in sunken panels decorated with vegetation and birds, it can also consist of figurative ornamentation such as at Vouneuil-sous-Biard, near Poitiers (Vienne, France, doubtless circa the end of the fifteenth century) This recent discovery proves the early existence of elaborate decorations in a Christian context outside Italy. On the basis of more than 2000 fragments, it has been possible to restore the figures of the saints under the arches[1].

In the ancient Western Roman Empire, we only have a very small number of fragments remaining from the 6th and seventh centuries. However, the kingdoms of Lombardy and the Carolingians have left us with some complete examples, especially in Italy. In Santa Maria in Valle in Cividale (mid eighth century), the western wall has retained its ornamentation along the cornices and moulded archivolts and especially the monumental figures of saints with large eyes fixed on the hieratical door, perhaps the work of the Byzantine stucco workers expelled by iconoclasm. Let us also mention from the same period the some twelve thousand fragments of stucco and painted rendering that were discovered at the dig at the Monastery of Saint Martin in Disentis (canton of Grisons or Graubünden, Switzerland). The work, which also has a Byzantine feel, had it seems, in addition to the classical figures of saints, a monumental representation of the Death of the Virgin and the Last Judgement, with angels blowing their trumpets. Here, stucco and painting are used closely together, hands and faces alone being treated in relief. At the end of the eleventh century, a similar procedure was employed to distinguish the face of St George in the chapel of Saint Michelin in the abbey church at Saint-Chef-en-Dauphiné (Isère, France). In Carolingian Italy, the use of stucco seems to have been widespread in association with painting such as at San Salvatore in Brescia or San Benedetto in Malles. Complete examples are rarer in the Frankish Empire. At Germigny-des-Près, at the beginning of the ninth century, the varied wall decoration showed diverse influences, sometimes from distant lands with borrowings from Oriental or Islamic art. Another work at Corvey-sur-Weser (Westphalia, Germany) bears witness to the wish to revive the most elaborate traditions of ancient art. In the upper chapel of the westwork, the preliminary traces of the mounting of stucco statues in high relief have been recently discovered.

The Romanesque period

During the Romanesque period, stucco was not totally supplanted by stone. In France, where it seems to have been little used, we find it an eleventh century example at Saint Rémi in Rheims (Marne) completing the sculptures around the capitals, and at the same period, as a decoration for the crypt in Saint-Jean-de-Maurienne (Savoie). The remarkable example in the abbey church at Alet-les-Bains (Aude), the following century, seems to be an isolated instance. The apse, which is beautifully finished in freestone of classical type, originally had in its interior a stucco decoration that was made to resemble closely the stone cornices outside. Its considered use doubtless owes more to the quality of the finish allowed by this technique than to its lower cost. This is perhaps the reason for its frequent utilisation in Italy in the twelfth century. One remarkable such example is for instance in San Pietro al Monte in Civate (Lombardy) with its west end, crypt and ciborium. In Northern Spain and Catalonia, the wall decorations, which are rare and very incomplete, sometimes borrow complex ornamental patterns from Islamic art.

We might complete this overview with a few German works (Saxony), from the end of the12th century. Two remarkable polychrome chancels preserved at Hildesheim and Halberstadt present an external decoration of blind arcades and saints in high relief. In the abbey church of Gernrode, a monumental Holy Sepulchre is decorated with scenes of after the Resurrection in which the almost life-sized figures are executed in an amazingly lifelike fashion. The material’s ease of use must have facilitated the quality of the work.

The rarity of preserved works and the low esteem in which they were held and which led to the paucity of studies dedicated to them until recently, all mean that we lack specific criteria for dating them and leaves some uncertainties. A good example is the celebrated statue of Charlemagne in the Carolingian church at Mustaïr(Switzerland), dated from 9th century by some and from the end of the twelfth century by others (following the canonisation of Charlemagne in 1165). Gothic art seems to have only small recourse to this technique, revived from the Renaissance onwards, and then in the eighteenth and nineteenth centuries, with the taste for plasterwork.

F. H. –S.

NOTE


[1] C. Sapin (dir.), Les stucs de l’Antiquité tardive du site de Vouneuil-sous-Biard, to be publ. in the review Gallia.