Citation link:
https://digi.ub.uni-heidelberg.de/diglit/arbeitshefte_blfd_31/0147
Peter Burman
Cathedral Church of St Andrew Wells: Inspection of two sculptures
from the West Front
(5th - 9th December 1983)
Angel (no. 311)
This carving is of extraordinary delicacy, the stone being Beer
of some very similar white limestone, which is bedded vertically
and has consequently lost carved detail from several of the front
planes.
J. Sampson has written an excellent description of its condition,
uncleaned; I fully concur with his analysis of the problem. The
entire surface has formed a skin (in some cases more than one
skin) which incorporates all the very finest details of the artist's
work. Salts are trapped underneath this skin, having crumbled
the stone immediately below it, so that the skin comes off hor-
ribly easily. Rather a lot has been lost already, fortunately most-
ly from the clouds which are more broadly carved than the
figure which rises out of them.
When examined under the microscope, at various magnifica-
tions from lOx to 60x, the skin has an oily appearance. For the
most part, the rusty-yellow layer underlies a blacker one, but
there is no true layer structure, as everything is clearly part of
the same block of stone. At first sight it appears that at least
some of the skin is the result of something applied to the stone,
such as oil; as it continues over many breaks and is certainly not
original. Indeed it varies in thickness having peeled off with the
surface and re-formed on the newly exposed stone so it may be
assumed to be the result of pollution. Chemical analysis is
necessary in order that the problem can be understood: samples
have been taken with this in mind.
Microscopic examination also revealed the considerable
deposits of salts all over the surface. A trial area on the clouds
was poulticed twice using Sepiolite (magnesium silicate earth)
and water; subsequent examination when dry at lOx and 30x
magnification showed that although the salts had largely been
removed from exposed porous surfaces, the were still stuck
under the crust.
A not very sanguine hope had been held out that some calcium
sulphate in the crust might have been softened by the poultice,
but it hardly made any visible difference. Test cleaning on un-
touched areas of crust, and on areas still damp from the
poultice, using 10% ammonia solution (880 ammonia plus
9 parts water), did not remove a great deal of black dirt. It
is not certain that the poulticed area was substantially cleaner
than the other area, and in neither case would enough of
the black pollution come off to make the surface look nice.
The problem is compounded by existing losses in the skin,
which make the shole sculpture look blotchy. (A cleaning
test using methylene chloride on the side of the halo was no help
at all.)
The following areas were examined with the microscope and
photographs and samples taken:
1. on the spalled edge of the scroll the surface was seen to have
turned black, there being no proper line between it and the
sound stone. Photo 60x. A curious buttercup-yellow deposit
was noted in a fissure here.
2. on a cloud, the crust was laminating itself away from a carv-
ed edge, in the following layers: the sound stone incor-
porated tiny black spots. On this lay a layer of salts mixed
with decayed stone. Next came a gummy looking brown
crust evidently impervious to moisture. On top of this was
more decayed stone mixed with salts, with a further very
black crust on the surface. Photo 20x.
3. on the dexter side of the face, the appearance of the crust
or skin is rusty-yellow (continuing thus on areas of flesh and
hair) up to the edge of the break where the front of the face
has come off. On the break the stone is blackened, and
looks gummy under the microscope. There are salts trapped
under the skin. Photo 20x.
3a. the same phenomenon was observed on the adjoining curl
of hair, where it is particularly obvious that the skin is part
of the stone. Photo 30x.
4. the dexter side of the halo has a thick, crumbly yellow skin
with white saltyness underneath, which adjoins smoother,
dirty stone. Photo lOx.
(I wonder if the indentations on the halo might have been
intended to receive glass «jewels» such as were common on
coronets and suchlike on effigies of about this period.)
5. on the sinister side of the face, some of the crusty yellowy
skin goes round and over the break. It springs off easily
bringing a layer of salts and stone with it. Photo lOx.
6. a sample was taken for analysis from a poulticed area of the
clouds to discover whether the salts have been reduced.
6a. from the layer of salts trapped under the crust, in case
someone is able to analyse them. I am not certain at present
who might do such analysis.
My own skills are those of a paintings conservator, not a stone
specialist. I have tried some obvious methods that might have
worked had the skin been the result of an applied layer, and also
satisfied myself that the problem consists of some chemical
change involving the most precious surface detail of the stone
itself. Unless some method can be researched of reversing this
change - and I know of none - I can envisage no possible way
of preserving this sculpture if it is put back on the West Front.
The action of rainwater on the salts under the skin will cause
the rest of the original detail to peel off, even if it is thickly
shelter-coated (so the minute detail would be smothered
anyway!) as the shelter-coat is porous and the crust impervious
to salts. To attempt to «clean» the figure, by taking off the skin
with all the original sculptor's surface, would be an act of van-
145
Cathedral Church of St Andrew Wells: Inspection of two sculptures
from the West Front
(5th - 9th December 1983)
Angel (no. 311)
This carving is of extraordinary delicacy, the stone being Beer
of some very similar white limestone, which is bedded vertically
and has consequently lost carved detail from several of the front
planes.
J. Sampson has written an excellent description of its condition,
uncleaned; I fully concur with his analysis of the problem. The
entire surface has formed a skin (in some cases more than one
skin) which incorporates all the very finest details of the artist's
work. Salts are trapped underneath this skin, having crumbled
the stone immediately below it, so that the skin comes off hor-
ribly easily. Rather a lot has been lost already, fortunately most-
ly from the clouds which are more broadly carved than the
figure which rises out of them.
When examined under the microscope, at various magnifica-
tions from lOx to 60x, the skin has an oily appearance. For the
most part, the rusty-yellow layer underlies a blacker one, but
there is no true layer structure, as everything is clearly part of
the same block of stone. At first sight it appears that at least
some of the skin is the result of something applied to the stone,
such as oil; as it continues over many breaks and is certainly not
original. Indeed it varies in thickness having peeled off with the
surface and re-formed on the newly exposed stone so it may be
assumed to be the result of pollution. Chemical analysis is
necessary in order that the problem can be understood: samples
have been taken with this in mind.
Microscopic examination also revealed the considerable
deposits of salts all over the surface. A trial area on the clouds
was poulticed twice using Sepiolite (magnesium silicate earth)
and water; subsequent examination when dry at lOx and 30x
magnification showed that although the salts had largely been
removed from exposed porous surfaces, the were still stuck
under the crust.
A not very sanguine hope had been held out that some calcium
sulphate in the crust might have been softened by the poultice,
but it hardly made any visible difference. Test cleaning on un-
touched areas of crust, and on areas still damp from the
poultice, using 10% ammonia solution (880 ammonia plus
9 parts water), did not remove a great deal of black dirt. It
is not certain that the poulticed area was substantially cleaner
than the other area, and in neither case would enough of
the black pollution come off to make the surface look nice.
The problem is compounded by existing losses in the skin,
which make the shole sculpture look blotchy. (A cleaning
test using methylene chloride on the side of the halo was no help
at all.)
The following areas were examined with the microscope and
photographs and samples taken:
1. on the spalled edge of the scroll the surface was seen to have
turned black, there being no proper line between it and the
sound stone. Photo 60x. A curious buttercup-yellow deposit
was noted in a fissure here.
2. on a cloud, the crust was laminating itself away from a carv-
ed edge, in the following layers: the sound stone incor-
porated tiny black spots. On this lay a layer of salts mixed
with decayed stone. Next came a gummy looking brown
crust evidently impervious to moisture. On top of this was
more decayed stone mixed with salts, with a further very
black crust on the surface. Photo 20x.
3. on the dexter side of the face, the appearance of the crust
or skin is rusty-yellow (continuing thus on areas of flesh and
hair) up to the edge of the break where the front of the face
has come off. On the break the stone is blackened, and
looks gummy under the microscope. There are salts trapped
under the skin. Photo 20x.
3a. the same phenomenon was observed on the adjoining curl
of hair, where it is particularly obvious that the skin is part
of the stone. Photo 30x.
4. the dexter side of the halo has a thick, crumbly yellow skin
with white saltyness underneath, which adjoins smoother,
dirty stone. Photo lOx.
(I wonder if the indentations on the halo might have been
intended to receive glass «jewels» such as were common on
coronets and suchlike on effigies of about this period.)
5. on the sinister side of the face, some of the crusty yellowy
skin goes round and over the break. It springs off easily
bringing a layer of salts and stone with it. Photo lOx.
6. a sample was taken for analysis from a poulticed area of the
clouds to discover whether the salts have been reduced.
6a. from the layer of salts trapped under the crust, in case
someone is able to analyse them. I am not certain at present
who might do such analysis.
My own skills are those of a paintings conservator, not a stone
specialist. I have tried some obvious methods that might have
worked had the skin been the result of an applied layer, and also
satisfied myself that the problem consists of some chemical
change involving the most precious surface detail of the stone
itself. Unless some method can be researched of reversing this
change - and I know of none - I can envisage no possible way
of preserving this sculpture if it is put back on the West Front.
The action of rainwater on the salts under the skin will cause
the rest of the original detail to peel off, even if it is thickly
shelter-coated (so the minute detail would be smothered
anyway!) as the shelter-coat is porous and the crust impervious
to salts. To attempt to «clean» the figure, by taking off the skin
with all the original sculptor's surface, would be an act of van-
145