LA-ICP-MS is a well acquainted technique for the quantification of a wide range of minor and trace elements present in
the glass matrix. The benefit to understand the changes in technological processes or the added value in assessing the
provenance and chronology of the raw glass material is however rarely discussed. By selecting a set of 197 Roman black
glass artifacts dating between the 1st and 5th century AD we aimed to contribute to this issue. The obtained data on the
production of glass artifacts helps better understand the constantly evolving patterns in glass consumption throughout the
Roman imperial period.
The key trace elements linked with the sand generally show the use of Levantine and Egyptian raw glass to produce
black glass artifacts and result in well defined clusters. These indications are evidence for the use of different raw glasses
in the Roman Empire and therefore featuring the work of diverse workshops over time. Specific trace elements such as
copper, cobalt and lead reflect the application of recycling glass in Roman times.
An extended set of 18th century glass vessels was analyzed by means of SEM-EDX (major and minor element
composition) The fragmented archaeological objects were recovered from a latrine belonging to the early 18th
century building phase of the nunnery of Clairefontaine, near Arlon (B). On the basis of typology and
decoration, the major part of the vessels could be dated around the middle of the 18th century. Variety in color
and weathering of the glass suggest differences in glassmaking recipes and in the composition and origin of raw
materials. The results of the analysis show how two main compositional groups constitute about 90% of the
analyzed glass set, and these are constituted by potash glass (transparent beakers) and high lime low alkali glass
(green bottles). Next to these, a few potash-lime and soda glasses are also found. The type of alteration has also a
clear relation with the original glass composition.
As far as Belgium and archaeological window glass is concerned, the most important site is the Dunes Abbey, a former
Cistercian abbey near the Flemish coastline. The collection contains approximately 15,000 fragments dating from the
13th to the 16th century. This glass was exposed to atmospheric weathering while in situ for several hundred years, buried
for up to 400 years, excavated by different individual excavators in different eras and for over half a century stored in
uncontrolled conditions. Moreover, different conservation treatments have been applied to the glass. Due to this, the
collection was in a friable condition and we assume half of it has already been completely lost. The remaining collection
retains fragments whose condition ranges between almost perfectly preserved material to being completely weathered to
the point that no original glass survives. In this research, an important asset is recognizing what has already been lost and
maximizing what is still available.
During recent conservation and stock making campaigns, the different weathering phenomena were separated into 9
groups based on empirical criteria and detailed registration. As a first step to further investigation of the weathering
processes, quantitative SEM-EDX analyses are used to give better insight into the chemical composition of these groups.
The aim is to bridge the gap between interpretative archaeologically and archaeological science and to develop a
common terminology to evaluate the complexity of weathering phenomena in archaeological window glass collections
which can be used as a tool for the assembling and interpretation of these collections.
SEM-EDX and LA-ICP-MS analyses were performed on a set of early 17th century London glass fragments. The
samples originate from two archaeological sites (Aldgate and Old Broad Street) where glass workshops were active in
this period.
The great majority of the samples are made of soda glass. Two distinct compositional groups are observed, each typical
of one site of provenance. The samples originating from the Old Broad Street excavation feature a silica-soda-lime
composition, with a moderate amount of potash. The samples from Aldgate are richer in potassium and feature higher
amounts of trace elements such as Rb, Zr and Cu. The distinction between the two groups stems from different flux and
silica sources used for glassmaking.
A comparison with different European glass compositions of that time reveals no resemblance with genuine Venetian
production, yet the composition of the Old Broad Street glass shows a close similarity to that of fragments produced ‘à la
façon de Venise’ in Antwerp at the end of the 16th century. This coincides with historical sources attesting the arrival of
glassworkers from the Low Countries in England and suggests that a transfer of technology took place near the turn of
the century.
In this publication optical spectroscopy is considered to be a supplementary technique to study ancient colored glass. It
results from a systematic study of the UV-VIS-NIR transmission spectra of intentionally colored glass fragments from
various archaeological and historical sites and dated from the Roman period to the 21th century AD. The main goal
consists of defining optical sensing parameters for this type of material. The considered colorants are iron, cobalt,
manganese, copper and chromium.
It is proved that many cases exist where optical spectroscopy can be seen as a straightforward, non-destructive, low-cost
and in-situ applicable technique in identifying authentic material or to obtain information about the origin of the material.
Possible sensing parameters are defined as the absence/presence of absorption bands characteristic for a specific coloring
metal oxide and the spectral position of these bands. These parameters could reveal information about the applied
furnace conditions and/or to the composition of the glass matrix. It is shown that the cobalt absorption band situated
around 535 nm for soda rich glasses (Roman and industrial times) is shifted towards 526 nm for potash rich glasses
(medieval and post-medieval times).
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