Composition and Technology of the 17th Century Stucco Decorations at Červená Lhota Castle in the Southern Bohemia

Author(s): Jan Válek, Olga Skružná, Petr Kozlovcev, Dita Frankeová, Petra Mácová, Alberto Viani, Ivana Kumpová
Paper category: Proceedings
Book title: Proceedings of the 5th Historic Mortars Conference
Editor(s): José Ignacio Álvarez, José María Fernández, Íńigo Navarro, Adrián Durán, Rafael Sirera
ISBN: 978-2-35158-221-3
e-ISBN: 978-2-35158-222-0
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 596-613
Total Pages: 18
Language : English

Abstract: The stucco decoration from the Great Chamber of the castle Červená Lhota in the
Southern Bohemia was surveyed and characterised as part of its planned conservation.
The repair works that are still to be specified in detail should be based on a good
knowledge of the original material and technique. The main focus was on the fruit
pieces decorating the ribs of vaults. Altogether, over twenty mortar samples were
collected from the vault bedding mortar, plaster, drawn elements and stuccos.
Additionally, some pieces of fruits, that were loose and had to be temporarily
removed, were studied macroscopically and by X-ray CT. Characterisation of binder,
aggregate and additives was carried out using TA, acid attack, sieve analysis of
unsolvable residue, XRD, FTIR and nL-MS. The characterisation led to understanding of
the uses of various mortar mixes and determination of their recipes. A typical fruit
piece was composed of an inner modelling core mortar made of lime-gypsum binder
and a coarser aggregate covered with a 5–20 mm think lime rich stucco layer
containing calcitic air lime and fine siliceous sand. This stucco mortar was also used for
modelling various small decorations - fine and thin shapes like leaves, cherries and
grapes. These were attached to the main piece by a fine adhesive mortar made of lime
and gypsum in various proportions. The use of gypsum and the differences in lime to
gypsum ratio corresponded to a certain functional requirements (performances). This
finding was a key parameter that contributed to the reconstruction of the original
application technique and procedure. Qualitative analysis of animal proteins
determined presence of collagen – an animal glue that was used to modify the setting
of gypsum and which was also used in the final finish. The results are discussed as an
example of a procedure that aims at a detailed replication of the original technique.
Keywords
Historic production, processing and application of mortars, renders and grouts, lime
technologies, stucco decorations

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00