Design and chemical composition of the Bohemian glass
produced from 14th till 18th century
Introduction
• chemical composition of the bohemian drinking glasses have been changed
simultaneously with the historical style changes (gothic, renaissance, baroque)
• the content of P2O5 (around 1 wt%) in the archaeological glass is the most
important indicator of using beech ash
• gothic glass has the worst chemical durability, corrosion is heaviest (total
corrosion and pitting)
Beginning of the glass production in Bohemia area is dated to the 12th century AD. The source of technological knowledge came from west Europe, where the
potassium glass (K2O-CaO-SiO2) production started around 8th century AD [1-3]. In Bohemia, so called woodash glass (from two compounds) was not
produced, but our forefathers produced woodash-potash glass very early (potash was leaching mainly from beech ash)[2]. Our laboratory had a possibility to
restore and analyze the archaeological glasses from the houses waste sumps from the towns Chrudim, Hradec Králové, Opava and castle Košumberk. Chemical
analyses were made both by SEM/EDS (in case of too small amount of sample) and XR Fluorescence methods (in case of the glass pieces without any corrosion
symptom and a sufficient sample amount).
Dana Rohanová, Jan Frolík*
Gothic style (14th - 15th AD) Baroque style (18th AD)Renaissance style (16th - 17th AD)
Corrosion symptoms
Chemical composition, average values [wt%]
Ratios of raw materials in
the batch [weight portions
on 100 kg SiO2]
SEM/EDS, XRF
OM
oxide SiO2 K2O CaO MgO Na2O MnO Al2O3 P2O5 Fe2O3 SO3 Cl As2O3 K2O/CaO
gothic 58,0 19,9 15,4 2,5 0,2 0,9 1,5 1,0 0,3 0,3 0,1 1,3
renaissance 60,7 13,7 17,2 2,2 1,1 1,0 1,8 1,0 0,5 0,2 0,2 0.8
baroque 74,8 13,4 9,6 0,2 0,9 0,1 0,2 0,1 0,1 0,2 0,2 0,3 1.4
dulling
Fe spots
iridescence
flaking cracking
iridescence
layer precipitation
Style/ingredients SiO2 beech-ash potash CaCO3 As2O5 MnO2 NaCl
gothic 100 70/80 30/20 0 0 0 0
renaissance 100 40/50 20/20 10/20 0 0 0
baroque 100 0 25 25 0,5 0,34* 0,25
Department of Glass and Ceramics, Institute of Chemical Technology Prague, Technická 5, 166 28 Prague 6
*Institute of Archaeology of the AS CR, v.v.i., Letenská 4, 118 01 Prague 1, Czech Republic
Total corrosion
Conclusions
Acknowledgments
* [3]
[1] Wedepohl K.H.: Glastech.ber.Glass Sci.tecnol.70(8) 246-
255, 1997.
[2] Cílová Z.: Sklář a keramik, 60(910-12): 199-204, 2010.
[3] Drahotová O., et al: Historie sklářské výroby v českých
zemích I, Academia, Praha, 2005.
pitting
This work was supported by GAČR : P 405/12/1411
Authors thanks for restoration work to students of the ICT
Prague at the program: Conservation and restoration of
historical object from glass and ceramics (R. Kozáková, L.
Klikarová, P. Dudková, V. Kumstová, L. Jeníková, V. Šimková, T.
Hüttnerová, T. Syrovátková)dana.rohanova@vscht.cz
Raw materials [3]: SiO2 (mainly quartz): beech ash: potash, later CaCO3 or Ca(OH)2
dulling
Reference