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Early Chemical Industries:

Sugar Manufacturing/Refining in the Middle East (Jordan)

Introduction
Sugar cane was introduced into the Middle East from the late 11th century as part of the so-called Islamic agricultural revolution; its cultivation an the technology involved in extracting cane sugar soon spread across many parts of the Mediterranean.

Excavations of sugar mills located notably in the Jordan Valley, Palestine and, for the later periods, Cyprus (von Wartburg 2001) have revealed substantial structural remains and which together with the ubiquitous sugar pots have provided much information on the main stages in the extraction process.

Fig. 1 Location map. Tawahin is arrowed

Tawahin es-Sukkar is well placed for a sugar mill, being situated on a small hill overlooking the large alluvial fan where the sugar would have grown; water came in from a nearby wadi, and the Lisan peninsular, rich in minerals, is nearby. Our recent excavations have uncovered the mill room, the water chutes, a low vaulted room and the large waste heap (Photos-Jones et al. 2002). The mill probably dates to the Mamluk period (12th-15th centuries AD).

Fig. 2 View (from the west) of the Tawahin on the hill in the foreground

Fig. 3 Tawahin site plan.  

Fig. 4 The mill room in the foreground and the two water chutes in the background

Production of sugar
The main steps in the production of sugar are: (1) crushing the sugar cane to extract the juice, (2) boiling the juice to give a syrup, (3) removal of both colour and non-sucrose substances, and finally (4) sugar crystallisation.

Methodological approach
An understanding of the two last stages of sugar processing, has been a particular goal of our research project. In the absence of archaeological evidence for these stages, the way forward has been to adopt a materials science approach: to characterise the components of the waste heap and the sugar pots. Careful excavation of the former revealed a complex stratigraphy of layers of ash, industrial waste, sugar pot fragments, charcoal, and sand and gravel.

Fig. 5 View from the NE of the waste heap.  

Fig. 6 Fragments of sugar pots and molasses jars from the excavations.

Sugar pots and the associated molasses pots (Fig. 7)
1. Production
The pots must have been mass produced, presumably locally although no kilns have not yet been found. Today clays occur close to the wadis as well as in the alluvial fan to the west of the site. The pots’ typology is still under study, however petrographic analysis reveals a number of calcareous fabrics, differing in quartz (Fig. 8), calcite and chert content. This may reflect no more than the use of different (local) clays over the lifetime of the sugar mill. Chemical analysis subsumes these various local fabrics into one chemical group.

Fig. 7 Sugar and molasses pots of the Crusader period from Acre (Stern 2001: Fig. 19)

Fig. 8 Photomicrographs of thin sections of two sugar pots. Note the different textures. x7 PPL

2. Function & Discard
Our working hypothesis is that the syrup, once it had been formed (step 2 opposite), was then ‘cleaned up’ with a clarifier, poured into the sugar pot, whereupon the molasses dripped into the jar below (Fig. 7) leaving the crystalline sugar in the pot at the top. Once the crystalline sugar had been removed, both pots were thrown away.

Some of the pot fragments, whether found in the waste heap or elsewhere, had incrustations or stains on the interior. Their analysis by X-ray diffraction and Fourier-transform IR spectrometry indicated that the concretions were calcite-rich, and the stains were iron rich; neither contained sucrose or traces of tri-carboxylic acids that are found in molasses. Any wax esters deriving from the sugar cane stem, if they had survived, would be present in too low concentration to be detected even probably by GC.

The ashy material that was so common in the waste heap had a similar mineralogical and chemical composition to the pale-coloured incrustation on the sugar pots: principally calcite, sometimes gypsum. A SEM image of one ash sample (TES 54) shows platy calcite aggregating as lumps (Fig. 12). After this sample had been dispersed in water, it became apparent that the sample also contained fragments of carbonised materials as well as organic remains resembling the cellular structure of sugar cane (Fig. 11).

An important observation was the presence of significant (> 400 ppm) strontium in the calcitic waste (Fig. 10) which links the source of the calcite to the Lisan. The sediments there are fine-grained calcite (and gypsum) which are found to contain high Sr (> 1000 ppm).

Fig. 10 SEM-SE image of Lisan sediment (AJH9) showing fine acicular calcite.

Fig. 11 SEM-SE image of TES54 following dispersion in water. Note the organic remains with a cellular structure resembling that expected of sugar cane.

Fig. 12 SEM-BS image of TES 54 displaying the bright small grains of strontium sulphate embedded in the calcite matrix.

We propose that the crucial mineral added to the murky brown syrup to help produce the crystalline sugar was fine-grained calcite. Many questions remain to be tackled, including whether (1) the clarification step was done in large vats and/or in the pots themselves, and (2) whether the process altered over time.

Authors: RE Jones, AJ Hall, University of Glasgow; E Photos-Jones, SASAA.

References:

1. Photos-Jones E, KD Politis, HF James, AJ Hall, RE Jones and J Hamer, 2002, The Sugar Industry in the Southern Jordan Valley: An interim report on the pilot season of excavations, geophysical and geological surveys at Tawahin as-Sukkar and Khirbat Ash-Shaykh Isa in Ghawr As-Safi, Annual Dept Antiq Jordan 46, 591-614.

2. Stern E, 2001, The excavations at Lower Horbat Manot: a Medieval sugar-production site, Atiqot XLII, 277-308.

3. Von Wartburg M-L, 2001, The archaeology of cane sugar production: a survey of twenty years of research in Cyprus, Antiquaries J. 81, 298-314.