Painted Islamic Beaker
by Aelfgifu verch Morgan
Where and When
This entry is an example of a medieval Islamic beaker painted with glass enamel. This type of vessel was in use in areas such as Syria, Egypt, Iraq, and Iran, and dates to somewhere between the 11th and 13th centuries.
Who Used Them
Enameled glass was the privilege of the rich in the medieval world. One of the glasses on which I based my design, the Luck of Edenhall was so prized that it traveled back to England from the crusades, and arrived with a specially made case and became the mascot of the margrove family. Other enameled and gilded glass is used for mosque lamps.
Decoration Design
I chose to base the design of my enameled beaker on that of a glass in the Freer and Sackler Galleries of Art, and the Luck of Edenhall, which is in the Victoria and Albert Museum. I chose a simplified floral and scroll design.
Luck of Edenhall. Syrian, 13th century CE. Victoria and Albert Museum.
Beaker. Syria, 1200 – 1300 CE. Freer and Sackler Galleries.
Form
The basic form of most Medieval Islamic glass beakers is a cylindrical glass, taller than it is wide, with a flared lip. Sometimes there is a small kick or larger band at the foot of the vessel, and the top usually flares out from the sides of the vessel an additional quarter to third of the vessels width.
Tools
The tools and techniques we use in glass blowing today are essentially the same type used in the Middle Ages. The basic tools of a glass blower include those used to actually melt and cool the glass and those used in forming it.
The tools used for heating and cooling are:
· a furnace to melt and hold glass
· a place to re-heat glass - either the mouth of the furnace or an additional heating area modernly called a “glory hole”
· An annealer to gradually cool off the finished glass so it doesn’t crack while cooling.
There are several different examples of medieval glass shops that can be observed in pictures and from descriptions, and they all include these heating and cooling tools. Unfortunately, while glass is available from most periods, all of the pictures and descriptions of tools, furnaces, and techniques are from later periods. In, On Divers Arts, written by Theophilus somewhere between the 10th and 12th centuries CE, methods for creating a furnace for working glass and for making an annealing furnace are described. [1]Another example is from a description and wood cut of a furnace from the Pirotechnia of Vannoccio Biringuccio: The Classic Sixteenth-Century Treatise on Metals and Metallurgy. [2]
The Pirotechnia of Vannoccio Biringuccio. Furnace for melting, working, and annealing glass. Woodcut.
As other illustrations of medieval glass shops include the same aspects – an annealer, a melt furnace, and a place to re-heat glass, and as these are necessary to the craft of glass blowing, it seems reasonable to assume that they would be part of any medieval glass shop. These furnaces were run off of wood, and fires were kept stoked by apprentices and workers who carefully watch the quality and heat of the fire. A modern glass shop such as the one where I made my glass consists of the same elements, but is run off of electricity and natural (or sometimes propane) gas for fuel, with regulators to do the jobs of the apprentices and workers.
The tools used for shaping the glass are:
- a blowpipe -on which to blow the glass
- a punty -on to which the glass vessel is transferred when it is time to open the mouth of the vessel
- a marver -a place to roll the glass to shape and cool it
- jacks -used for cutting in necks and pulling necks on bottles
- tweezers -used for pulling out bits of glass
- shears -used for cutting and trimming glass
These tools can be seen in medieval illustrations in manuscripts. Here a glass blower can be seen blowing through a pipe and marvering the bubble of glass on some sort of flat surface.
Depiction of a forest glass shop from Sir John Mandeville’s Travels, Dated 1420 – 1450. British Library, London.
Tools and techniques have also been mentioned in descriptions. One particularly good description is from the The Pirotechnia of Vannoccio Biringuccio (pg. 130-131):
It (glass) is worked by being blown by men’s breath with certain iron tubes... With one of these they take the glass from the pot by attaching it to the point and then wrapping it around... and giving it the form of a large ball. The first thing they do after withdrawing it is to press it on marble, turning it over and over so that it unites. The blowing on it through the opening of the tube they make it like a bubble and they elongate it by swinging it about their heads... and finally, in short, they give it the form of the vessel which they wish by warming and blowing, by pressing and enlarging. Then separating it from the first tube they take hold of it again at the bottom with the other (tube) and improve it, cutting its mouth with a pair of shears...”
These are the same type of tools used today in glass blowing, and what I used in creating my glass.
Glass
Most glass shops imported glass from other areas to use in furnaces. Usually glass would be melted down into ingots near a source of materials, and then exported. Then it would be crushed up into “cullet” to use in the glass furnace for re-melting, occasionally raw materials would be shipped and combined in the glass furnaces, and this is modernly called “batch”. Glass from failed attempts which was not polluted by colored glass would usually be saved, crushed, and re-melted in the form of “cullet”. Such glass was sometimes even exported from places like Syria to Venice. [3] [4] [5]The shop where I blow glass buys it in the form of batch, and adds in recycled glass in the form of cullet, in a similar fashion to some medieval glass houses.
The glass I use is one of the types of glass made in the Middle Ages. There were three major kinds of medieval glass, pot-ash glass, soda-lime glass, and high-lead glass. All three types of glass were used through the medieval world, depending on what materials were available. The glass used in the shop where I blow glass is soda-lime glass. The usual temperature for the working range of medieval soda-lime and pot-ash glass was around 1800 - 2000 degrees Fahrenheit. The glass I use is workable at temperatures between about 1900 and 2100 degrees Fahrenheit. [6] [7]
Enamels
I have not yet been able to locate a medieval glass enamel recipe, but have experimented with modern glass enamels, both glass based and acrylic based. I was most successful with the glass I painted using Porcelain glass paints. I painted a glass with the same design using Reuche glass enamels which fire onto the glass at a temperature of 1050 degrees Fahrenheit and had problems with the enamels running, even after numerous tests.
Works Cited
Jacoby, David. “Raw Materials for the Glass Industries of Venice and the Teraferma, About 1370 – 1460.” Journal of Glass Studies. Vol. 35. Corning, New York.1993. pg. 67,
Smith, Cyril Stanley, Martha Teach Gnudi (translated by). The Pirotechnia of Vannoccio Biringuccio: The Classic Sixteenth-Century Treatise on Metals and Metallurgy. Dover Publications, Inc. New York. 1990.
Theophilus On Divers Arts. Translated by John G. Hawthorne, Cyril Stanley Smith. Dover Publications, Inc., New York. 1979.
Toso, Gianfranco. Murano: a History of Glass. Arsenale Editrice. 2000.
Tyson, Rachel. Medieval Glass Vessels Found in England c AD 1200-1500. Council for British Archeology Report 121. 2000.