Summary and outlook

This volume deals with the study of two Roman glass works in the Lower Town of Augusta Raurica. The starting point is the analysis of the excavations carried out in 1974 (excavation 1974.003) and 1978 (excavation 1978.004) in a region called 'Äussere Reben' in the present-day village of Kaiseraugst. The excavated areas were located on either side of the district road, to the southwest of a junction. The two Roman roads concerned are today called Glasstrasse and Unterstadtstrasse. The sites adjacent to the roads are called Region 17B (excavation 1978.004) and Region 17C (excavation 1974.003).

Both sites yielded the corner of a building extending beyond the excavation trenches. Each building contained a factory workshop with furnace structures. Based on numerous remains of furnaces, some of which still showed remnants of glass, and innumerable fragments of glass-melting pots, it can be positively stated that glass was processed in both buildings and that the features uncovered were the remains of two glass works.

The site chosen for the construction of the glass workshops in the Lower Town of Augusta Raurica was characterised by a peripheral location and proximity to two bodies of flowing water, the Rivers Ergolz and Rhine. This location was probably also chosen because of a port presumed to have been located nearby and its convenient situation close to cross-country roads.

The emphasis of this study is placed on the examination of the technological aspects of Roman glass processing and the interpretation and reconstruction of the glass furnaces unearthed.

Preliminaries

The volume begins with the analysis of the excavations carried out in 1974 and 1978 (pp. 13 ff). The features were processed and published according to the guidelines set out in the 'Manual for the analysis and publication of excavations in Augst and Kaiseraugst'. These guidelines stipulate that the features must be given codes and that a catalogue of features must be prepared.

The identification code is made up of the following elements:
Type of feature (Fdm = Fundament [foundation], G = Grube [pit], Gr = Graben [ditch], Gsch = Grubenfüllschicht [pit filling], Fst = Feuerstelle [hearth], Of = Ofen [furnace {here glass furnace}], MR = Mauer [wall], Pf = Pfostenloch [post hole], Sch = Schicht [layer], So = sonstige Strukturen [other features]),
Type of overall structure (ARE = Areal [area], GEB = Gebäude [building], LAG = [Militär-]Lager [{military} camp], POR = Portikus [portico], UNT = Unterstadtstrasse, GLA = Glasstrasse),
Location within excavation (Regions 17B and 17C),
Location within overall structure (defined rooms 01, 02, 03 etc.),
Time period or construction stage (A, B, C, D, E),
Building phase (a, b, c etc.),
Renovation phase (1, 2, 3 etc.),
Feature number (1, 2, 3 etc.).

The excavated features

The features can be attributed to three distinctive construction phases described in detail in the part of the publication dealing with the structures uncovered (pp. 13 ff). The first phase (construction stages A and B) covered the lifespan of two military camps (after AD 40 to around AD 50/60). These features are not dealt with in this volume³⁵². The second phase (construction stage C) covers the period after the demolition of the second military camp, during which the site lay idle (around AD 50/60 to around AD 100; pp. 18 ff). During the third phase (construction stages D and E), the road network was set up and stone buildings were constructed on the site (construction stage D: from c. AD 100; pp. 19 ff). This was the period during which the glass workshops were installed, initially in Region 17B (pp. 20 ff), and later in Region 17C (pp. 30 ff). During construction stage E, these buildings were demolished or altered (after AD 220; pp. 34 ff; a table with an overview of the features can be found on pp. 44 f).

The glass workshops and glass furnaces

Part II deals with the glass works and with glass processing in general in the area of Kaiseraugst-Äussere Reben (pp. 47 ff).

One chapter gives a detailed description of the glass furnaces uncovered (pp. 47 ff).

The remains of 14 furnaces, some of which overlay one another and contained alterations, were identified in the workshop in Region 17B (excavation 1978.004; pp. 47 ff). Three different types of furnace could be identified:

Of particular significance was the discovery of the tank furnaces, which have been rarely found to date. In Roman times, this type of furnace was mainly used for the production of raw glass, i. e. for making glass by melting quartz sand, which raises the question as to whether this was also the case in Augusta Raurica. While there is no clear evidence for this, raw glass production cannot be excluded with absolute certainty (on the interpretation of glass furnaces cf. pp. 72 ff, on the reconstruction cf. pp. 80 ff).

From a relative-chronological point of view, there are indications that a tank furnace was replaced by two round furnaces combined with an annealing furnace. According to this pattern, the 14 furnace structures can be attributed to five time periods. Based on a lifespan of six years for each furnace, one may assume that the workshop in Region 17B was in operation approximately 25 years from the second quarter to around the mid 2^nd century (around AD 130 to around AD 160; pp. 88 ff).

Contrary to the workshop in Region 17B with its 14 glass furnaces, the workshop in Region 17C (excavation 1974.003) yielded certain evidence of only one furnace (p. 71),
- a round furnace: glass furnace 15.

This workshop appears to have been in operation at a later date than that on the other side of the road in Region 17B. It was probably used into the first quarter of the 3^rd century.

The chapter on the tools contains a detailed study of the glass-melting pots found (pp. 91 ff). Among these pots that were used for melting the glass, four types could be identified (pp. 92 ff, Fig. 103):
- Type 1: glass-melting pots with everted rims,
- Type 2: glass-melting pots with thickened upright rims,
- Type 3: glass-melting pots with upright rims (with nondescript rim shape) and
- Type 4: glass-melting pots with club rims.

The shapes of the rims of these pots are very similar to those of contemporary coarse ware in Augusta Raurica. The melting pots very often had a coat of clay on the outside, the intention of which was obviously to prolong their life spans. The insides of the pots showed remnants of green glass in various shades from light to dark green. Two or three pots fitted into a round furnace. One may assume that these vessels were not built into the furnaces but that some of them gradually fused with the furnace walls over time.

Possible remains of punty irons and a weighing scales from the excavated area can be associated with the production of glass (pp. 106 f). The fact that no blowpipes or whole punty irons were found indicates that the tools were handled with great care and that the workshop was abandoned in an organised manner. Impressions and marks on glass fragments show that pincers were used.

The glass finds from the workshops (pp. 107 ff) can be categorised as raw material, processing and production waste, i. e. misshapen pieces, and glass for recycling. All these categories were represented in the material found. It was not usually possible to differentiate between production waste and glass for recycling. Apart from two lumps of raw glass of a different colour, all these glass finds were green.

While for the workshop in Region 17B with its 14 furnaces one may postulate the production of green square bottles (type AR 156/Isings 50) and various other vessel shapes of an intense dark green, almost black colour (poss. pot type AR 104.3/Trier 37, aryballoi type AR 151.3/Isings 61 variants, conical beakers type AR 70/Isings 109a/b and parallel-sided beakers type AR 98.1/Isings 85b) and of mosaic tesserae (pp. 114 ff), the range of shapes produced in the workshop in Region 17C with just one furnace could not be identified due to a lack of diagnostic finds. The output of products from the glass works (pp. 118 ff) probably exceeded the needs of the colony town and the excess was sold in the surrounding areas.

Synthesis

The synthesis chapter brings together both parts of the study and provides information on the location of the glass workshops (pp. 123 f) as well as thoughts on their size and design (pp. 124 f), and their organisation (pp. 125 ff).

The Kaiseraugst glass works were conveniently located in the Lower Town of Augusta Raurica in the immediate vicinity of the Rivers Rhine and Ergolz and the arterial road from Basle to Vindonissa. The river location guaranteed an optimal supply of raw materials. The demand for wood was particularly great. On the other hand, rivers were also important for transporting glass products.

The workshop in Region 17B with its 14 furnaces initially extended over an area of approximately 162 m², and was later reduced to 145 m². Compared with other industrial areas in Augusta Raurica, this was an extraordinarily large factory workshop. Its roof was possibly supported by timber posts. The earliest glass furnaces were located along the west wall. Over the course of time, the furnaces were moved to the centre of the hall. This may have been done to shorten the distances between the melting and annealing furnaces. Ashes and fragments of demolished furnaces were obviously dumped in a pit within the factory hall. It is possible that hot ashes were used to further cool down the glass products after they were taken out of the annealing furnaces, but this cannot be proven.

The workshop in Region 17C with just one furnace covered an area of 138 m² and thus was somewhat smaller than the neighbouring glass works in Region 17B. The question as to why this workshop only had one glass furnace although at least two furnaces, i. e. a melting and an annealing furnace, would have been necessary to maintain a smooth workflow cannot be answered. It is possible that this was a small workshop producing essences that were sold in small glass bottles blow-formed in situ, or perhaps a jewellery workshop where glass beads were made.

The glass works in Region 17B started its operation with two pot furnaces. Recycled and raw glass were probably processed initially. Later, a tank furnace was built and used to melt recycled glass gathered locally or raw glass imported from further afield. The glass lumps produced were further processed in two newly built pot furnaces and probably blown to make glass vessels. The products were cooled down in an annealing furnace. Based on an assumed lifespan for each furnace of approximately six years, and taking into account overlapping of the various glass furnaces, the period of operation can be estimated to have been around 25 years.

The glass works were probably family-run businesses with few employees. The core of the staff consisted of one or several glass-makers. The owner of the workshop, a male or perhaps a female glass-maker, not only decided on the range of products and the amount turned out, but also determined the assignment of tasks within the business. One may assume that people specialised in certain tasks. In the glass works the year was probably divided into two halves: the furnaces were in operation from spring to autumn, while repairs were carried out and new furnaces built during the winter months.

The wares produced were probably sold in a sales room near the glass works or directly from the workshop. However, it is also possible that the products were retailed by a middleman.

Outlook

Future studies on the glass workshops in Augusta Raurica should concentrate on the glass furnaces and in particular on the annealing and tank furnaces; only rare examples of the latter have to date been discovered and published. Particularly in the case of the tank furnaces, scientific analyses of the preserved furnace components could identify more precisely the temperatures that were reached within the furnaces, which in turn would allow us to draw conclusions regarding their specific use. The central question in this case would be whether the tank furnaces served to melt recycled glass or to produce primary glass. If the Kaiseraugst tank furnaces did, indeed, produce primary glass from raw materials, the next question would concern their provenance and availability. Where did the glass-makers source the sand suitable for the process? How was it transported to Augusta Raurica? Why was primary glass production discontinued? Was there a shortage of raw materials? Was it not possible to import large enough amounts of sodium carbonate? Was the production too costly?

It would require experiments to ascertain whether the glass furnace reconstructions proposed in this volume (pp. 80 ff) could have been fully functional. In the case of the round furnaces, one possible type of construction and operation was actually confirmed by an experiment. As regards the annealing and tank furnaces, such confirmation has yet to be obtained.

With regard to the glass vessels made on site in Augusta Raurica, a comparative study of the glass fragments found in the colony town and its surroundings might provide more information about the extent of the production and about potential trade routes. A comprehensive analysis of the commercial area in and around Region 17 in the Lower Town of Augusta Raurica would also have considerable merit.

Translation: Sandy Hämmerle