MOLISE - S. Vincenzo al Volturno
FILE: Monastery of  S.Vincenzo al Volturno 1
TITLE: Fragments of window-glass (about 7000); hundreds fragments of glass-working wastes; mosaic-tesserae, crucibles, frit, etc.

 

LOCATION:  Laboratorio Archeologico, Comune di Castel S. Vincenzo, Molise

DIMENSIONS: The most of the window-glass is cylinder-blown; only a very limited percentage is crown-made. The reconstructed panels are often slightly irregular with regard to geometrical shapes, but rectangles (in a few cases with a curved edge, measuring about cm 9-12 x 15-16), right-angled triangles (about cm 14-16 x 8-12), right-angled trapezoids (about cm 15 x 13) and one crown-made disc (cm 13 of diameter), have been identified. The most common panel shape appears to be rectangular. The thickness is about mm 1-6.   See Plate with the geometric figures identified in the reconstructed panels.

PROVENANCE: The window-glass fragments have been recovered during several archaeological campaigns, started in 1980 and still going on.

During the 1980-86 excavations coloured window-glass was recovered in the Original nucleus of the Monastery : the Crypt Church (trenches B,C and FF), the South Church/Distinguished Guests’ House (trenches A and G), the Monks' Refectory, the Distinguished Guests’ Refectory and the Garden Court (trenches X and D/X), the Vestibule (trench D), on the site of the late Roman tower (trench F), in the area of the hilltop cemetery (trench S and T).

A certain number of fragments werw found in the Garden Court in burnt layers (phase 5c) and in eleventh-century demolition layers (phase 6b) A large quantity was found in four concentrations within the drain D 552 (phase 6) in the Garden Court .They must have formed part of those windows which have remained in situ after the fire of 881 and which were finally demolished together with the wall during the eleventh century. The distance between each concentration of glass scatter is c. two meters suggesting a total number of 13/15 windows in the Monks Refectory overlooking the Garden Court. See Plan of the funds along the Refectory north wall.

A noticeable quantity and variety of glass-working waste came to light in trench FF, along the south atrium wall of San Vincenzo Maggiore, where the phase 5 (early ninth century) workshops were located. Many small panes, entirely preserved (one of these is a Fragment rhomboidal shaped), were also found here to be employed for liturgical furnishing (transennae, lamps); see Plan of the workshops along the south atrium wall of S. Vincenzo Maggiore.  A certain number of window-glass fragments come from the site of the phase 8, late eleventh- to early twelfth-century abbey, on the eastern side of the river Volturno, where Gerard rebuilt San Vincenzo a fundamentis (1981 excavations of trenches K, L, M, Abbey Survey 1982, Abbey Ploughing 1991, 1994-96 excavations of the Atrium).

CHRONOLOGY: The group of finds coming from the old nucleus of the monastery, in front of the Ponte della Zingara, has been related with the building enterprises of abbot Joshua (792-817), Talaric (817-24) and Epiphanius (824-42). It was infact absent from the layers dated until the late eight century (phase 3), instead was present in tre stratigraphy associated with the mentioned works (phases 4 and 5 a, b and c). Window-glass has been found also in robbing trenches dug by the monks themselves to collect building material during the eleventh-century (phase 6b) and finally in contexts pertaining the late eleventh- and early twelfth-century monastery newly built on the other side of the river Volturno by the abbot Gerard (1076-1109). On the history and the stratigraphy of the monastic settlement.

AUTHOR: No other site in Europe has offered testimonies of such a varied and skilled glass working. For this reason it remains under question the provenance of the artisans. There is no written source to support any hypothesis, but if they did not come from the Near East, certainly it was from a place where still these techniques, most of Roman tradition, where still practised for a demanding public.

ASSIGNEMENT: the Abbots of the Monastery

SUBJECT/S: the main part of the late eight-ninth-century fragments is without any traces of painting or decoration; including some Samples with marbled effects. Instead the new feature observable in the New Abbey glass is painting, a sort of grisaille. Out of 279 fragments, 55 show traces of painting (19,7% of the total number) see  Graphic of the panels of the New Abbey.

CRITICAL NOTES: Perhaps one of the most remarkable aspects relating to the window-glass was the discovery of the workshops were it was worked during the ninth century. If glass was not produced at San Vincenzo from raw materials, at least there is evidence that glass was worked in vast quantities and that it was one of the important aspects of its industrial activity until the moment of the Arab attack of 881 (phase 5c). Glass was employed not only for the production of window panes but also of very refined vessels, enamels and settings for jewellery, and liturgical object. But the discovery of these glass fragments is certainly the one of most outstanding interest: early Medieval window panes are strikingly rare from Western Europe, althoug already around the 470 A.D. Sidonius Apollinaris was celebrating a basilica in Lyon where glazed-windows were decorated "with figures" (Ep. II, 10, 4, Sidonius Hesperio suo salutem). In the Life of saint Liudger of Münster in Westfalia, of the middle ninth cent., it is told about a blind girl that obtains sight thanks to a miracle and the first thing she sees is the figurative stained-glass of a chapel (Vita III. sancti Liudgeri (lib. II, cap. 31). So as, not to forget are the painted fragments of late eighth cent. from Paderborn (Gai, 2001), Rouen (Le Maho, 2001) and Farfa (Newby, 1991), that testify the origins of painted, figurative stained-glass already in the Carolingian period.

Most of the traits observed in the glass from San Vincenzo are typical of the cylinder-glass, produced with the so-called cylinder-method, which was invented in the East Mediterranean in the first century BC. and then spread all over the Roman Empire. Previous to this invention, glass was cast or roller-moulded (Harden 1961: 39 ff.). One of the main characteristics of cylinder-glass is the presence of tiny gas-bubbles in parallel rows, created by blowing a broad bulb that is given a cylindrical form by blowing and manipulation (Theophilus, cf. Dodwell 1986: 42). Then the end of the bulb was pierced and the aperture widened to equal the bulb's greatest diameter. The opening was then pinched together so that a pontil could be attached with a seal of glass. Next the bulb was knocked off the blowing-pipe and the other end widened out. The cylinder was detached from the pontil, cut longitudinally with iron shears when still hot, and finally flattened in the annealing kiln on a surface covered with sand. This is the Roman method, still in use in the West in the twelfth century, as it is attested by a treatise on The Various Arts, written in Germany by a monk who calls himself Theophilus. He speaks about a further step in the process: the cylinder was cut only when cold and then reheated to be flattened (cf Dodwell 1986: 41-2). The result of this cooling phase is the difference of appearance between the recto and the verso of the cylinder-glass: one is fine, smooth and the other mat, with tiny ripples creating sort of wave patterns. In fact, the upper surface of glass, in contact with the air, cools quicker than the inner layers and develops a sort of rippled "skin". The recto instead owes its smoothness to the polished surface on which it is flattened. Harden (1961: 41) thinks that it was an iron plate surfaced with sand, but it is more likely to imagine the use, in early Middle Ages, of the more available stone instead of costly and rare iron. Furthermore there is not any archeological evidence of iron-plates found in glass-furnace contexts. At San Vincenzo this was probably a polished marble slab, since marble spolia was diffusely present in the early Medieval monastery. Still nowadays, at the blown-glass factory Hartley Wood (Sunderland, England), a polished stone is used to flatten the open cylinder. Occasionally the sand spread on the slab has left marks on the recto of the pane. The thickness of sherds varies between 1-6 mm and is very variable also within the same panels, because of the artisan production method, which makes reconstruction difficult. During the excavations many edge-sherds were found, which are U-shaped, straightly cut or grozed. In fact, the original edges of the flattened cylinder were rounded by the furnace's heat, becoming in section U-shaped. The rectangular pane obtained by flattening the cylinder was cut into smaller panels by drawing a pointed tool across the surface and then splitting the glass with the hands. Cutting tools leave nearly imperceptible marks and create straight, sharp, edges, very difficult to distinguish from simply broken ones. The shape of panels could be refined by using the grozing-iron, a tool with a curved end that produces "flint"-like edges. The method for cutting and trimming the panels is described also by Theophilus (cf Dodwell,1986: 47-9). Though the majority of the window-glass found at San Vincenzo in phases 4-5 and in phase 8 levels is of the cylinder type, a few fragments appear to have been produced with the crown method. The percentage of cylinder glass of all glass found in trenches B, C, D, P, S, T (phases 4-5, ninth century) is 99,46 %, therefore the crown-glass found was 0,54%. The shapes of the most part of the glass- window are triangles, rectangles, right angled trapezoid.  These fragments settled in pairs of the same shape and color formed the window-glass structure; as proves the discovery of a window-gass collapsed by fire of 881; see A "Glass-window" all'antica. [page not yet available in E  nglish]

The crown-method consisted in blowing a bulb of glass with a hollow iron pipe, opening it at the bottom and then by twirling it with the pipe until it took the shape of a disc. The centre of the disc, having been attached to the blowing-pipe, was much thicker then the rest of it - the thickness decreases towards the flame-rounded edge - and called "bull's eye". Crown-glass is in fact recognisable by air bubbles in a spiral formation, created by twirling the glass, and by its varying thickness. The most beautiful example found at San Vincenzo are the Fragments of one blue disc, some of which have a spiral decoration due to the twirling of the mass of glass with the blowing-pipe, after having impressed the glass in a mould with longitudinal "teeth" (see catalogue 11). The presence of crown-glass in an early Medieval western context is of outstanding interest, because, after having been a typical product of the Roman glass industry, it seems to have been uncommon in the West during early Middle Ages (Harden 1972: 83-84; Dell'Acqua, 1997 b: 36-37; Whitehouse, 2001: 34).

It is not possible to say whether the glass working continued to be practised by the monks after their return to the site (c. 914) or if it had been reintroduced at San Vincenzo during the late eleventh century. A certain number of window-glass fragments come from the site of the phase 8, late eleventh- to early twelfth-century abbey, on the eastern side of the river Volturno, where Gerard rebuilt San Vincenzo a fundamentis. He was a young monk at Monte Cassino, and perhaps he was influenced by the building programmes of his "master", the famous abbot Desiderius of Monte Cassino. Here coloured glazed windows were present, as referred by Leone Marsicano (Chronica monasterium Casinensis, lib. III, capp. 10, 27, 28, 33,). The working area in the New Abbey site has not been yet identified, although wastes of glass-working (even a piece of frit) have been found spread around the area. The percentage of cylinder glass found on the New Abbey site (phase 8, twelfth century) is 93,5 %; crown-glass 6,4 %. Some of the glass has shown a sort of painting, the so-called grisaille, that appears whitish, and in some cases has only left shades on the glass. The monk Theophilus describes the method of preparing the grisaille with copper, green and blue glass, urine or wine. This mixture could be used to trace designs on glass panes with brushes of different thicknesses, after which it needed to be fire-tempered to be fixed on the support. Then the treatise suggests to check the results of the tempering by trying to scratch the grisaille: if it does not come off it means that it is durable, having penetrated the upper layer of the glass (Dodwell 1986: 49-53). The painting seems to have been used to create geometrical (for example, cat. no. 78, 81) or foliate motives (cat. no. 69, 70, 87), although some lines could be interpreted as part of draperies (for example, cat. no. 41, 59, 86), or human facial features (cat. no. 102).

CONDITIONS: At San Vincenzo sodium-based glass with a stable fabric has been discovered in the fragments of window-glass and of enamel worked in the workshops of San Vincenzo (Freestone-Bimson, Appendix, in Mitchell-Hansen, 2001). The glass paste do not show any visible signs of decay but has manteined its transparency and surface sheen. The relative percentages of the main ingredients -soda, calcium and silica, have proved to be almost identical to those of Roman imperial glass. Only a content of lead of less than 1% in the glass from San Vincenzo differentiate it from typically Roman glass in which this element is absent. Moreland (1985: 50) thought that the possibility of using the sand from the Volturno may have been an incentive for the creation of a glass workshop, though this would not explain which alcaline flux, of an equal quality, could have been found to substitute Egyptian natron. Regarding the reuse of Roman glass debris, it is remarkable that in early Medieval site investigated to date have accumulations of this material wiating to be melted been found, much the less at San Vincenzo where only mosaic tesserae and fragments of vessel glass found in the ninth century levels may be of Roman date. It may be that the material of the ninth century from San Vincenzo and that from the Cappella Palatina built at Salerno by the Longobard prince Arichis II (758-87) may both have been imported from temporary manufacturing sites on the near Eastern coast towards Langobardia minor, especially since recent analysis carried out by Freestone have revealed that it is not possible to distinguish these in terms of composition (Freestone, personal comment).

Glass samples from the New Abbey site have revealed soda as the main alkali, although potash appears in increasing percentages (2-3%) compared to the ninth century glass (Freestone, personal comment). This would indicate that newly produced glass was used in the production of glass for the New Abbey. However, it is possible that the ninth century glass was also used to accelerate the fusion of the new the compound, since only very few fragments have been found in certain parts of the monastery (for instance the "South Church"), suggesting that this was collected during the course of the spoliation of materials for reuse during the twelfth century. The glass from the New Abbey seems to be of a more fragile fabric compared to the older material, with a certain number of fragments -seemingly especially those of a lighter colour- covered by a layer of silica gel, a symptom of decay of the glass surface occuring in glass containing potash.

BIBLIOGRAPHY: see BIBL S. Vincenzo al Volturno

PHOTOGRAPHIC REFERENCE : Hodges-Mitchell, 1996; Dell’Acqua-James, 2001.

EDITOR: Francesca dell’Acqua aprile 2002