Gebs, Chiselled Gypsum Plaster

The highest expression of the plasterer's art in the Islamic tradition is achieved with the humblest of tools.
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The word "Gebs" (الجبس) literally means "gypsum" in Arabic. The carving of gypsum plaster as a means of decoration came to be refined and proliferate as an art form during the Late Middle Ages. It is associated almost exclusively with the Moors, specifically the Islamic culture of the North African Maghreb as well as the Iberian Peninsula that included modern day Spain and Portugal. It is generally agreed that the highest expression of the art is to be found at the 14th century Nasrid palace of the Alhambra at Granada; the patterns and craftsmanship there remain an infinite source of inspiration. Nevertheless, Gebs very much continues as a living tradition practised at a high level of craftsmanship both in restoration and for new commissions in modern day Morocco.

Bou Inania Madrasa, Fes

Bou Inania Madrasa, Fes

The subject matter of Gebs follows that of Islamic decoration generally. The most widespread application is for geometric designs that are likewise found in "zellige", the coloured tile decoration. Arabic calligraphy is also a common application of chiselled gypsum plaster, either to express passages from the Qur'an or Arabic poetry. However, in comparison to wood or stone, gypsum plaster is so well adapted to be carved in organic, curvilinear forms that vegetal decoration of highly stylised scrolling vines, leaves and flowers are an almost distinguishing feature of this medium.

Recently I had opportunity to meet and observe artisans working at the Alhambra followed by some personal hands on carving with a master craftsman in Fes, Morocco. With this all still fresh in mind, I'd like to share some of the practical means and methods and underlying design principles of the Gebs tradition.

Door surround in Fes

Door surround in Fes

Mise en Œuvre

Today, as Gebs is mostly used in interiors the widely available Plaster of Paris, low fired gypsum plaster is used. However, for much of the historic work exposed to the exterior an impure gypsum was fired at higher temperatures resulting in a slower initial set but greater density and resistance to efflorescence and weathering. At a minimum the plaster should be applied to a thickness of 3/4"; however, the best work will be carved deeply and may require a plaster application of up to two inches thick. Gypsum plasters have an initial set anywhere from mere minutes to a few hours. Typically, the plaster application is carried out a day before the design is transferred and the carving begins. The plaster will take a week or two depending on ambient humidity to dry fully. During this time, it is highly workable and the working time can be extended if necessary by continuing to saturate the plaster each day. The initial set renders the surface hard enough to carve while the moisture content within keeps it workable and prevents it from becoming too brittle and prone to fracture.

Hand forged chisels and dividers

Hand-forged chisels and dividers

Designs are worked out ahead of time using compass and rule on paper. The designs are then transferred by inscribing lightly into the surface of the plaster with a set of dividers. Often a template is prepared to more readily convey at least some of the basic information; however, it only serves as a loose guide, most of the decisions have to be made by the artisan in the moment of carving. Similar to stone carving, a line is established from which you excavate towards, not from the line. However, the plaster chisels are hand held; there is no hammer. And unlike wood, the plaster is completely homogenous and consistent so there is no grain to consider. As a result, there is markedly more control and nuance that can be achieved in carving plaster than these other materials. Another advantage is that if minor mistakes are made, gypsum plaster is a material that can be "pointed", that is to say touched up readily. A little careful sanding here and there after the plaster has fully dried can also remove textural imperfections. Customarily, a couple of coats of a clay wash are applied to antique the surface without sealing it.

The chisels needed are simple but specific. They are thin, relatively long and come in various widths of high carbon forged steel. It is critically important that the heads are rectangular and that the shafts do not taper. The chisels can be used alternatively to gouge, cut like a knife or smooth like a small spatula. Although work can be done as panels in a studio for affixing on site, the best and most enduring work is done in situ.

The Alhambra Palace

The Alhambra Palace

Basic Design Principles

Essentially Gebs is bas relief work using gypsum plaster as a medium. Thus, many of these principles are generally applicable to relief work whereas a few are very specific or characteristic of Gebs. Contrast is obviously a basic principle shared across many mediums: large/small motifs, straight/curved elements, smooth/textured surfaces. Closely related to this is depth; shallow chiselled surface will read lighter whereas deeply carved surfaces will result in dramatic shadow. This interplay of light and shadow is critical to reading the design.

Gebs in action

Gebs in action

Most Islamic patterns are based on four-fold or six-fold geometry; both the square and regular hexagon can interlock with themselves to completely fill a plane. This property can be used to play with the many possible internal symmetries by utilising subtle adjustments of contrast and colour. Particularly for abstract geometric designs the grid or frame is given more attention than the safts (petals) or stars that it encloses. In the best work this frame is given the impression of interlace, that of a woven tapestry. Interlace is expressed again, albeit differently in vegetal designs; the tendrils of vines will weave in and out of themselves or other elements. Finally, in the best and often oldest work we see the masterful use of polychromy, bright painted colours and gold leaf.

A decade ago, I came to Marrakech to study another Moroccan plaster tradition, Tadelakt. I was completely seduced and overwhelmed by the Gebs designs I saw at that time, never imagining that I would have opportunity to learn this craft. However, since that time I’ve completed an apprenticeship in stone carving and spent many years studying Islamic design that have prepared me for this moment. Presently, we’re in discussions with artisans in Granada, Spain and Fes, Morocco about conducting workshops and diffusing this incredible art further afield.

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