Dr. Olivier SCHALM, Prof. Dr. Koen JANSSENS,
University of Antwerp, Dept. of Chemistry, Antwerp (Belgium)
Hilde WOUTERS, Instittuut voor het Archeologisch Patrimonium, Asse-Zellik (Belgium)
Danielle CALUWÉ, Free University of Brussels, Dept. Of Archaeology, Brussels (Belgium)
Composition of 12th-18th Century Window Glass in Belgium: Non-Figurative Windows in Secular Buildings and Stained-Glass Windows in Religious Buildings
Table I a: Average composition (in % w/w) of 434 HLLA glass samples, grouped into five clusters by means of hierarchical clustering.
The listed uncertainties corresponds to the 1s standard deviation on the average concentration values. The cluster symbols are used again in Fig. 5, Fig. 6 and Fig. 7. With each cluster, a hypothetical sand:ash ratio can be associated while in some cases, the use of an additional third compound (NaCl) as starting material can be assumed. (?)
| Cluster name | A  |
B  |
C  |
D  |
E  |
|---|---|---|---|---|---|
| 12-14th century | 15-17th century | ||||
| -31 | -59 | -62 | -182 | -100 | |
| Na2O | 0.5 ± 0.3 | 1.0 ± 0.6 | 2.5 ± 0.6 | 0.7 ± 0.6 | 3 ± 1.2 |
| MgO | 4.3 ± 0.3 | 3.7 ± 0.3 | 3.8 ± 0.4 | 3.5 ± 0.5 | 3.0 ± 0.5 |
| Al2O3 | 3.1 ± 0.5 | 3.7 ± 0.8 | 3 ± 1 | 3.9 ± 0.9 | 3.3 ± 0.7 |
| SiO2 | 47 ± 1 | 56 ± 2 | 58 ± 1 | 59 ± 1 | 61 ± 2 |
| P2O5 | 2.1 ± 0.6 | 2.7 ± 0.8 | 2.6 ± 0.5 | 2.2 ± 0.7 | 2.1 ± 0.7 |
| SO3 | 0.3 ± 0.1 | 0.2 ± .2 | 0.2 ± 0.2 | 0.2 ± 0.1 | 0.2 ± 0.2 |
| Cl | 0.02 ± 0.03 | 0.2 ± 0.1 | 0.4 ± 0.1 | 0.2 ± 0.1 | 0.5 ± 0.1 |
| K2O | 12 ± 1 | 7.1 ± 0.9 | 5 ± 1 | 7 ± 1 | 4 ± 2 |
| CaO | 28 ± 2 | 23 ± 1 | 22 ± 1 | 21 ± 2 | 21 ± 2 |
| MnO | 1.2 ± 0.2 | 1.2 ± 0.6 | 0.9 ± 0.2 | 0.8 ± 0.2 | 0.7 ± 0.2 |
| Fe2O3 | 0.7 ± 0.2 | 1.1 ± 0.4 | 0.9 ± 0.2 | 0.9 ± 0.3 | 1.0 ± 0.4 |
| BaO | 1.0 ± 0.2 | 0.5 ± 0.2 | 0.6 ± 0.2 | 0.5 ± 0.1 | 0.4 ± 0.1 |
| sand:ash ratio | 01:02 | 02:03 | 02:03 | 01:01 | 01:01 |
| Extra NaCl | none | small amount | large amount | small amount | large amount |
Table I b: Average composition (in % w/w) of 47 potash glass samples, grouped into three clusters and of five soda glass samples (in one cluster) by means of hierarchical clustering.
The listed uncertainties corresponds to the 1s standard deviation on the average concentration values. The cluster symbols are used again in Fig. 5, Fig. 6 and Fig. 7. With each cluster, a hypothetical sand: ash ratio is associated.
| Cluster name | F  |
G  |
H  |
I  |
|---|---|---|---|---|
| 13-14th century | 15-17th century | 18th century | Soda glass | |
| -10 | -35 | -2 | -5 | |
| Na2O | 0.5 ± 0.4 | 1.8 ± 0.9 | 2 ± 2 | 13 ± 1 |
| MgO | 3.5 ± 0.4 | 5.9 ± 1 | 0.06 ± 0.08 | 2 ± 1 |
| Al2O3 | 1.5 ± 0.8 | 1.8 ± 0.7 | 0.9 ± 0.4 | 1.9 ± 0.5 |
| SiO2 | 48 ± 3 | 56 ± 3 | 67.3 ± 0.5 | 67 ± 2 |
| P2O5 | 1 ± 2 | 2.6 ± 0.8 | 0.1 ± 0.1 | 0.2 ± 0.2 |
| SO3 | 0.4 ± 0.3 | 0.2 ± 0.2 | 0.2 ± 0.2 | 0.2 ± 0.1 |
| Cl | 0.1 ± 0.1 | 0.3 ± 0.1 | 0.1 ± 0.1 | 0.7 ± 0.4 |
| K2O | 21 ± 5 | 13 ± 2 | 19 ± 1 | 4 ± 2 |
| CaO | 22 ± 2 | 16 ± 2 | 10 ± 1 | 10 ± 3 |
| MnO | 1.1 ± 0.5 | 1.1 ± 0.7 | 0.1 ± 0.2 | 0.4 ± 0.1 |
| Fe2O3 | 0.5 ± 0.2 | 0.7 ± 0.2 | 0.13 ± 0.02 | 0.6 ± 0.2 |
| BaO | 0.5 ± 0.2 | 0.4 ± 0.2 | 0.11 ± 0.01 | 0.08 ± 0.04 |
| sand:ash ratio | 1:2 | 2:3 | 1:1 | 1:1 |
