DOI Heft:
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DOI Seite / Zitierlink:https://doi.org/10.11588/diglit.51152#0204
202
tion, softening of the foundations by ground water is being
prevented by sealing and drainage measures. The Lias, with
its high sulphate content, is particularly significant from a
hydrogeologicalpoint ofview, in so far as the crystallization
of salts in the ground water, rising due to capillary action,
has severely damaged the historical building materials, in
particular the cloister.
Angelika Gervais, Klaus Gervais and Jochen Lepper
Varieties of natural stone in the cloister,
their characteristics, uses and geological origins
In the cloister of St. Michael’s church in Hildesheim rocks
deposited in the Mesozoic were used. Properties such as Sedi-
mentation and petrographic and mineralogical characteri-
stics of siltstones and streaked Rhaetic sandstone from the
cloister, as well as sample materialfrom open-cut stone quar-
ries in the area surrounding Hildesheim are described. Two
other varieties of natural stone used in the Middle Ages are
presented and recent replacement material from the Jurassic
and Cretaceous Periods are briefly discussed. The historical
quarrying, use and origin of natural stones are described.
The origin of the uniformly fine Rhaetic sandstone used in
the cloisters in the immediate environs of Hildesheim is pro-
ven with the help of geochemical analysis.
Ivo Hammer, Caroline Assmann and Nils Mainusch
State of preservation and damage
from a conservation-restoration viewpoint
The cloister is in an endangered condition: the surface ofthe
Rhaet Sandstone, ofwhich most ofthe remaining medieval
architectural sculpture is made, is to a great extent pulveri-
sed. The replacements on the east wall carried out under C.
W Hase already show significant deterioration. The surface
is unevenly covered with a black gypsum-containing crust
and in some areas a thin cement-wash. The main cause of
the damage is not the risingground moisture, but rather the
hygroscopic effect of the existing accumulation of salts,
which is triggered by fluctuations in the climate and which
can have an expolsive effect. To a considerable extent, the
deterioration is due to the use of damaging materials in the
restoration work carried out under Hase, as well as to the
direct weathering of the vaults afier the bombing on 22nd
March 1945, which dramatically accelerated the normal
weathering process. Düring the last 10 years comparatively
little dramatic damage seems to have occurred. Although the
deterioration process has slowed down, it is evidently still
acute, which makes interventive Conservation measures
necessary.
Jörg Seele
The significance of climatic and environmental
influences
Environmental influences can damage historical monu-
ments. Climatic factors such as air temperature, relative
humidity, precipitation, wind, Insolation or frostplay apart.
Ifthese factors are combined with further influences, such as
salt accumulation in the structural parts, damage mecha-
nisms are triggered off which lead to the progressive destruc-
tion of these parts. In the cloister ofthe St. Michael’s church
in Hildesheim, climatic measurements have been taken for
the period of one year. They are currently continued for the
purpose ofgaining exact knowledge ofthegiven local condi-
tions. The results permit an evaluation of the individual
damage factors, such as theproblems caused by condensation,
or by thermal and hygroscopic fluctuations. It has been ascer-
tained that the combination of humidity fluctuations with
the given accumulation of harmful salts is a substantial
damage factor to the cloister. For this reason, there is a need
for measures which restrict and slow down the deterioration
processes, such as reducing the salt rate, or reducing the cli-
matic strains. For the purpose of preserving the historical
building substance, a protective shelter has been planned.
Currently, the effectiveness ofthis technical solution is being
monitored.
Erwin Stadlbauer, Rolf Niemeyer and
Hans-Jürgen Schwarz
An overview of damage factors and
damage processes
The various factors contributing to the weathering of natu-
ral stone can be divided into three groups, depending on
physical, chemical and biological processes. These processes
don’t begin in buildings, but already occur in the quarry
and also in the deepest zones of the earth’s crust. Weathering
of the exposed natural stone and mortar surfaces in the clois-
ter represents a complex, synergistic combination of different
processes that have resulted in extensive changes to the mate-
rials and caused their deterioration. The scale and intensity
of the damage is variable, depending on the type of rock and
the extent of exposure. The examination results indicate
that the building materials in the cloister have been dam-
aged primarily by humidity and the harmful effects of an
accumulation of salts. Therefore, not only urgently required
conservation-restoration stabilization measures will be car-
ried out in the current project, but also the possibility of
structural stabilization using a protective enclosure will be
tion, softening of the foundations by ground water is being
prevented by sealing and drainage measures. The Lias, with
its high sulphate content, is particularly significant from a
hydrogeologicalpoint ofview, in so far as the crystallization
of salts in the ground water, rising due to capillary action,
has severely damaged the historical building materials, in
particular the cloister.
Angelika Gervais, Klaus Gervais and Jochen Lepper
Varieties of natural stone in the cloister,
their characteristics, uses and geological origins
In the cloister of St. Michael’s church in Hildesheim rocks
deposited in the Mesozoic were used. Properties such as Sedi-
mentation and petrographic and mineralogical characteri-
stics of siltstones and streaked Rhaetic sandstone from the
cloister, as well as sample materialfrom open-cut stone quar-
ries in the area surrounding Hildesheim are described. Two
other varieties of natural stone used in the Middle Ages are
presented and recent replacement material from the Jurassic
and Cretaceous Periods are briefly discussed. The historical
quarrying, use and origin of natural stones are described.
The origin of the uniformly fine Rhaetic sandstone used in
the cloisters in the immediate environs of Hildesheim is pro-
ven with the help of geochemical analysis.
Ivo Hammer, Caroline Assmann and Nils Mainusch
State of preservation and damage
from a conservation-restoration viewpoint
The cloister is in an endangered condition: the surface ofthe
Rhaet Sandstone, ofwhich most ofthe remaining medieval
architectural sculpture is made, is to a great extent pulveri-
sed. The replacements on the east wall carried out under C.
W Hase already show significant deterioration. The surface
is unevenly covered with a black gypsum-containing crust
and in some areas a thin cement-wash. The main cause of
the damage is not the risingground moisture, but rather the
hygroscopic effect of the existing accumulation of salts,
which is triggered by fluctuations in the climate and which
can have an expolsive effect. To a considerable extent, the
deterioration is due to the use of damaging materials in the
restoration work carried out under Hase, as well as to the
direct weathering of the vaults afier the bombing on 22nd
March 1945, which dramatically accelerated the normal
weathering process. Düring the last 10 years comparatively
little dramatic damage seems to have occurred. Although the
deterioration process has slowed down, it is evidently still
acute, which makes interventive Conservation measures
necessary.
Jörg Seele
The significance of climatic and environmental
influences
Environmental influences can damage historical monu-
ments. Climatic factors such as air temperature, relative
humidity, precipitation, wind, Insolation or frostplay apart.
Ifthese factors are combined with further influences, such as
salt accumulation in the structural parts, damage mecha-
nisms are triggered off which lead to the progressive destruc-
tion of these parts. In the cloister ofthe St. Michael’s church
in Hildesheim, climatic measurements have been taken for
the period of one year. They are currently continued for the
purpose ofgaining exact knowledge ofthegiven local condi-
tions. The results permit an evaluation of the individual
damage factors, such as theproblems caused by condensation,
or by thermal and hygroscopic fluctuations. It has been ascer-
tained that the combination of humidity fluctuations with
the given accumulation of harmful salts is a substantial
damage factor to the cloister. For this reason, there is a need
for measures which restrict and slow down the deterioration
processes, such as reducing the salt rate, or reducing the cli-
matic strains. For the purpose of preserving the historical
building substance, a protective shelter has been planned.
Currently, the effectiveness ofthis technical solution is being
monitored.
Erwin Stadlbauer, Rolf Niemeyer and
Hans-Jürgen Schwarz
An overview of damage factors and
damage processes
The various factors contributing to the weathering of natu-
ral stone can be divided into three groups, depending on
physical, chemical and biological processes. These processes
don’t begin in buildings, but already occur in the quarry
and also in the deepest zones of the earth’s crust. Weathering
of the exposed natural stone and mortar surfaces in the clois-
ter represents a complex, synergistic combination of different
processes that have resulted in extensive changes to the mate-
rials and caused their deterioration. The scale and intensity
of the damage is variable, depending on the type of rock and
the extent of exposure. The examination results indicate
that the building materials in the cloister have been dam-
aged primarily by humidity and the harmful effects of an
accumulation of salts. Therefore, not only urgently required
conservation-restoration stabilization measures will be car-
ried out in the current project, but also the possibility of
structural stabilization using a protective enclosure will be