Tài liệu Gsa finearts sculpture docx

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2.3
Weathering steel
Outdoors
Force One: Consciousness is
Crucial by John Paul Rietta
Richard H. Poff Federal Building
Roanoke, VA
McKay Lodge Fine Arts
Conservation Laboratory, Inc.
Left: Before conservation: Note
the evidence of loose, flaky corro-
sion called “pack out” due to poor
drainage and moisture.
Right: During conservation: Note
how the sculpture is elevated to
allow airflow.
Understanding:
The following advice applies when a sculpture is composed totally or partially of weathering steel.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Corten is one brand of weathering steel and the word is
often used to identify all weathering steels. Almost all weathering steel sculpture is placed
outdoors. Weathering steel is usually left uncoated to purposely corrode. While the corrosion
generally looks like rust, weathering steel can often be identified by a purple color in some of its
corrosion. Generally, it is a darker color than the corrosion on mild steel. The corrosion should be
thin, hard, and tightly bonded when mature and stable. When left exposed to air, the corrosion,
which looks like rust, actually builds to a protective layer that prevents further corrosion. When
this protective layer is disturbed, by scrapes for example, the corrosion process will begin again
and “heal” itself. Removal of some forms of graffiti from weathering steel may require the
thinning or other disturbance of this protective corrosion. If so, the film will develop again,
though it may take two years for it to match the oldest film. However, this disruption of the
stable corrosion is to be avoided. When the weathering steel is constantly exposed to moisture,
such as near the ground, in shade, or where water puddles, the corrosion activity may not cease
but continue in a metal-depleting process that is more aggressive than the rust on common steel.
Weathering steel constructions that form hollow containers often have holes drilled to allow
condensed moisture to escape. These holes, if present, should be kept open. Also, salts used for ice
control lead to damaging corrosion processes. Salting of sidewalks should be kept as far from
weathering steel as possible. Weathering steel is sometimes painted. Paint can hold moisture in
place against the steel and create the damaging corrosive environment just mentioned. Painted
weathering steel must be inspected carefully for this condition and must always be completely
coated. The following problems and maintenance actions are the only ones that can safely be
performed by those with no specific training.
2.3
Cyclic actions:
Soiling. Hose off accumulated dust, bird droppings, salts from ice control, and other materials.
Rain alone does not do this effectively. Soils and invisible contaminants can be damaging. Only if
there is physical weakness, such as from broken welds, is it not safe to direct a stream of hose
water on a weathering steel sculpture. Forceful sprays of water using a jet nozzle are otherwise safe
and desired. Use the force of the water to remove thick accumulations in pockets where rain does
not reach. Rinse thoroughly from top to bottom. This washing can be every week if necessary but
should be at least once a year. Frequency depends on rate of soiling accumulation. Washing more
frequently than the average frequency of rain storms in the area where the sculpture is located
may not be desirable. However, during a dry summer, keep up the washing as the average annual
frequency of rain storms may be once every two to three weeks. Observed soiling should largely
drive the frequency of washing. A general rule calls for rinsing sculpture whenever the plaza is
washed down with a hose.
Graffiti. Paint and pen graffiti, oil stains, and tar deposits are difficult to remove completely from
weathering steel because these media often penetrate into the corrosion layer. It is important,
however, to try to remove as much as possible, as some graffiti seems to attract more. Restrict
your removal method to cloths and solvents. Use knit fabric cloth instead of woven or terry cloth
as coarse corrosion will collect fibers. Solvents available from hardware stores that would be
effective include acetone and methyl ethyl ketone
(MEK). Solvents will also dilute graffiti paint,
causing it to penetrate deeper into some corrosion. This is unavoidable. In time these stains tend
to diminish. Thick applications of paint can be removed using any of the solvent-based
commercial paint strippers. Peel-Away 1, available from Sherwin Williams paint dealers, is a
nonsolvent paint remover that can be used and is very effective. It has a very high pH (alkaline) as
it is made from sodium hydroxide. Follow the package directions. This is safe to use on the steel
but do not follow with the recommended acid wash. Instead, rinse the steel thoroughly with a
hose after completing the procedure.
Drainage. If weep holes for drainage exist at the lower parts of forms, clear them of clogging by
inserting a wire or stick into the holes. Report any clogged weep holes that can not be cleared.
Do not:
■ Do not wash with a pressure washer.
■ Do not sand, brush, or abrade the protective corrosion on the steel unless directed to do so by a
supervisor for a particular problem. Do not clean with any product other than the solvents and
paint strippers mentioned or with plain water. Do not apply any coating whatsoever.
■ Do not use Prosoco maintenance products (1) without clearing their use with a supervisor, (2)
without testing, and (3) without prior experience in the use of the product. Prosoco products are
often very effective but can damage materials not specifically within their range of application.
2.3
Weathering steel
Indoors
Assume that sculpture, because it is art, falls outside the range of application even though it may
be made from the same materials the Prosoco product was meant to treat.
■ Scratched graffiti should just be left alone to gradually form a new protective corrosion layer. Do
not sand or abrade to blend in the scratches without permission from a supervisor.
Watch for:
Look for loose, flaky corrosion (called “pack-out”). This damaging corrosion is a sign of continued
moisture. There may be a remedy for this condition. Report evidence of this to the supervisor.
Refer to “Four maintenance principles for all cases,” section 2.2
Understanding:
(See Weathering Steel
—
Outdoors for more information).
The following advice applies when a sculpture is composed totally or partially of weathering steel.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Artists choose weathering steel for outdoor installations
because of the stability of its surface corrosion. However, some of these sculptures have been
moved to indoor exhibits after they have naturally developed the stable corrosion film that
actually protects the steel from further corrosion. Great care must be taken to protect this stable
corrosion as it can only form again in an outdoor environment. It cannot be artificially created
except by imitation with colorants and these are not a good substitute for the real thing.
Cyclic actions:
Soiling. Dust with soft brushes only or a soft bristle vacuum attachment.
Graffiti. Graffiti removal from a sculpture indoors is not expected to be a part of cyclic
maintenance as it can be with outdoor sculpture. However, procedures using solvents to remove
marks described under Weathering Steel
—
Outdoors are safe to perform indoors if there is adequate
ventilation. Use knit fabric cloth instead of woven or terry cloth as coarse corrosion will collect
fibers. Solvents may leave stains when used locally on weathering steel kept indoors. It may be
necessary to apply them overall for an even effect. The overall look of the sculpture may change
(darkening is likely) due to residual effects of solvent penetration into the corrosion but the
change, if even overall, would not be considered detrimental as the surface of a weathering steel
object is natural.
Do not:
■ Do not use water or paint removers that need water for rinsing. The use of water may activate the
corrosion locally, leading to a visual deviation where applied that may take many years to diminish.
2.3
2.4
Bare mild steel
Outdoors
■ Do not sand, brush, or abrade the protective corrosion on the steel unless directed to do so by a
supervisor for a particular problem. Do not clean with any product other than the solvents
mentioned. Do not apply any coating whatsoever.
Watch for:
There is not likely to be deterioration indoors to watch for.
Refer to “Four maintenance principles for all cases,” section 2.2
Understanding:
The following advice applies when a sculpture is composed totally or partially of bare mild steel.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Some sculpture has been created with low carbon or “mild”
steel
—
the common industrial grade of steel and often in the form of reused industrial objects. In
nearly all cases, the artist purposely allows a rusted surface. However, there are cases where artists
applied an oil coating after creating the sculpture in an attempt to stabilize the corrosion. In most
of these cases, the oil is ineffectual but has left a degraded, darkened or peeling film. Whether
there are the remains of a former coating does not alter the maintenance recommendations below.
Cyclic actions:
Soiling. Hose off accumulated dirt, bird droppings, salts from ice control, and other materials.
Only if there is physical weakness
—
such as from broken welds
—
is it not safe to direct a stream
of hose water on a steel sculpture. Forceful sprays of water are otherwise safe and desired. Use the
force of the water to remove thick accumulations in pockets. This washing can be done every
month if necessary but should be at least once a year. Frequency depends on rate of soiling
accumulation. Washing more frequently than the frequency of rain storms in the area where the
sculpture is located is not desirable. Observed soiling should solely drive the frequency of washing.
Graffiti. Paint and pen graffiti are difficult to remove completely from rusted steel because these
media often penetrate into the corrosion layer. It is important, however, to try to remove as much
as possible as some graffiti seems to attract more. Restrict your removal method to cloths and
solvents. Use knit fabric cloth instead of woven or terry cloth as corrosion will collect fibers.
Solvents available from hardware stores that would be effective include acetone and methyl ethyl
ketone
(MEK). Solvents will also dilute the paint, causing it to penetrate deeper into some
corrosion. This is unavoidable. In time these stains tend to diminish. Thick applications of paint
can be removed using commercial paint strippers. Peel-Away 1, available from Sherwin Williams
paint dealers, is a nonsolvent paint remover that is very effective. It has a very high pH (alkaline)
as it is made from sodium hydroxide. Follow the package directions. This is safe to use on the
2.4
Bare mild steel
Indoors
steel but do not follow with the recommended acid wash. Instead, rinse the steel thoroughly with
a hose after completing the procedure. It is expected that rubbing with a solvent-soaked cloth will
remove loose corrosion and this is acceptable in the higher priority of removing graffiti.
Drainage. If weep holes exist at the lower parts of forms, clear them of clogging by inserting a
wire or stick into the holes. Report any clogged weep holes that cannot be cleared.
Do not:
■ Do not wash with a pressure washer.
■ Do not sand, brush, or abrade the protective corrosion on the steel unless directed to do so by a
supervisor for a particular problem. Do not clean with any product other than the solvents and
paint strippers mentioned or with water.
■ Scratched graffiti should just be left alone to gradually form new corrosion. Do not sand or
abrade to blend in the scratches without permission from a supervisor.
■ Do not use Prosoco maintenance products (1) without clearing their use with a supervisor, (2)
without testing, and (3) without significant experience in the use of the product. Prosoco
products are often very effective but can damage materials not specifically within their range of
application. Assume that art falls outside the range of application even though it may be made
from the same materials the Prosoco product was meant to treat.
Watch for:
Look for loose, flaky corrosion (called “pack-out”), especially at the joins between pieces of steel.
This damaging corrosion is a sign of continued moisture, and there may be a remedy for it.
Report evidence of this to the supervisor.
Refer to “Four maintenance principles for all cases,” section 2.2
Understanding:
The following advice applies when a sculpture is composed totally or partially of bare mild steel.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Some sculpture has been created with low carbon or “mild”
steel
—
the common industrial grade of steel and often in the form of reused industrial objects.
Such sculpture is normally exhibited outdoors but some are indoors. In nearly all cases, the artist
purposely allows a rusted surface. However, there are cases where artists applied an oil coating
after creating the sculpture in an attempt to stabilize the corrosion. In most of these cases, the oil
is ineffectual but has left a degraded, darkened or peeling film. Whether there are the remains of a
former coating or not does not alter the maintenance recommendations below.
2.4
Soiling. Dust with soft brushes only or a soft bristle vacuum attachment.
Graffiti. Graffiti removal from a sculpture indoors is not expected to be a part of cyclic
maintenance as it can be with outdoor sculpture. However, procedures using solvents, not water,
to remove marks described under Bare mild steel
—
outdoors are safe to perform indoors allowing
for the need for ventilation. Use knit fabric cloth instead of woven or terry cloth as coarse
corrosion will collect fibers. Solvents may leave stains when used locally on corroded steel kept
indoors. It may be necessary to apply them overall for an even effect. The overall look of the
sculpture may change (darkening is likely) due to residual effects of solvent penetration into the
corrosion but the change, if even overall, would not be considered detrimental as the surface of a
corroded steel object is natural.
Do not:
■ Do not use water or paint removers that need water for rinsing. The use of water may activate the
corrosion locally leading to a visual deviation where applied that may take many years to
diminish.
■ Do not sand, brush, or abrade the corrosion on the steel unless directed to do so by a supervisor
for a particular problem. Do not clean with any product other than the solvents mentioned. Do
not apply any coating whatsoever.
Watch for:
There is not likely to be deterioration indoors to watch for.
Refer to “Four maintenance principles for all cases,” section 2.2
2.4
2.5
Bare aluminum
Outdoors
Understanding:
The following advice applies when a sculpture is composed totally or partially of bare aluminum.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Aluminum forms a stable white or light gray corrosion
outdoors, which is usually a thin powdery film. The thin, powdery white corrosion should be left
untouched. A different type of corrosion forms small pits in aluminum. Both are normal, and the
pitting corrosion is usually not problematic. However, damaging corrosion can, in rare instances,
corrode aluminum into a weak, expanded and flaky sheet, especially near ground contact or in
salt environments.
Cyclic actions:
Soiling. Hose off accumulated dirt, bird droppings, salts from ice control, and other materials.
Only if there is physical weakness, such as broken welds, is it not safe to direct a stream of hose
water on an aluminum sculpture. Forceful sprays of water are otherwise safe and desired. Use the
force of the water to remove thick accumulations of dirt in pockets. This washing can be every
month if necessary but should be done at least once a year. Frequency depends on rate of soiling
accumulation.
Graffiti. Paint and pen graffiti are difficult to remove completely from aluminum because even
mild rubbing with a cloth will remove the stable white aluminum oxide and can polish the metal.
It is important, however, to try to remove as much as possible as some graffiti seems to attract
more. Restrict your removal method to cloths and solvents, using a very gentle touch. Stop if the
aluminum begins to discolor or gloss. Allow the solvents, strippers, and the rinse solvents or water
to perform nearly all the work. Solvents available from hardware stores that would be effective
include acetone and methyl ethyl ketone
(MEK).
Drainage. If weep holes for drainage exist at the lower parts of forms, clear them of clogging by
carefully inserting a wire or stick into the holes. Report any clogged weep holes that can not be
cleared.
Do not:
■ Do not wash with a pressure washer.
■ Do not use commercial aluminum cleaners.
■ Do not use nonsolvent paint strippers.
Refer to “Four maintenance principles for all cases,” section 2.2
2.5
Bare aluminum
Indoors
Majesty of Justice by Carl Paul
Jennewein
U.S. Department of Justice
Washington, DC
Norton Art Conservation, Inc.
Left and Right: During
conservation: showing details of
cleaning with a cotton swab.
Understanding:
The following advice applies when a sculpture is composed totally or partially of bare aluminum.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Aluminum forms a stable white or light gray corrosion
outdoors which is usually a thin powdery film. The thin, powdery white corrosion should be left
untouched. A different type of corrosion forms pits in aluminum. Both are normal, and the
pitting corrosion is usually not problematic. Aluminum indoors usually develops no condition
problems; however, dust accumulations and graffiti may require cyclic maintenance attention.
Cyclic actions:
Soiling. Dust with soft brushes only or a soft-bristle vacuum attachment. For greasy marks,
follow solvent treatments described under “Graffiti” below.
Graffiti. Paint and pen graffiti are difficult to remove completely from aluminum because even
mild rubbing with a cloth will remove the stable white aluminum oxide and can polish the metal.
It is important, however, to try to remove as much as possible, as some graffiti seems to attract
more. Restrict your removal method to cloths and solvents, using a very gentle touch. Stop if the
aluminum begins to discolor or gloss. Allow the solvents, strippers and the rinse solvents or water
to perform nearly all the work. Solvents available from hardware stores that would be effective
include acetone and methyl ethyl ketone
(MEK).
Do not:
■ Do not use commercial aluminum cleaners.
■ Do not use nonsolvent paint strippers.
Refer to “Four maintenance principles for all cases,” section 2.2
2.5
2.6
Stainless steel
Outdoors
Understanding:
The following advice applies when a sculpture is composed totally or partially of stainless steel.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Stainless steel is generally problem-free outdoors, but art
made from stainless steel will accumulate dirt and marks, and sometimes graffiti, which call for
cyclic attention. Be aware that small rust like spots or general orange stains of corrosion do form
on stainless steel. Do not attempt to remove this corrosion as it is not a problem. There are
various finishes to stainless steel that call for some specialized, periodic attention such as polishing
and mild abrasive cleaning. Report concerns about deteriorated original finishes but do not
attempt to restore a finish without instructions specific to the sculpture.
Cyclic actions:
Soiling. Hose off accumulated dust, bird droppings, salts from ice control, and other materials.
Rain alone does not do this effectively. Only if there is physical weakness, such as broken welds, is
it not safe to direct a stream of hose water on a steel sculpture. Forceful sprays of water using a jet
nozzle are otherwise safe and desired. Use the force of the water to remove thick accumulations in
pockets where rain does not reach. Rinse thoroughly from top to bottom. This washing can be
performed weekly if necessary but should be done at least once a year. Frequency depends on rate
of soiling accumulation, but washing cannot be overdone. A general rule calls for rinsing
sculpture whenever the plaza is washed down with a hose.
Graffiti. Paint and pen graffiti, oil stains, and tar deposits can be removed from stainless steel, but
aggressive rubbing during the removal process must be avoided so as not to burnish the metal. It
is important, however, to try to remove as much as possible as some graffiti seems to attract more.
Restrict your removal method to cloths and solvents. Solvents available from hardware stores that
would be effective include acetone and methyl ethyl ketone
(MEK). Thick applications of paint
can be removed using any of the solvent-based commercial paint strippers. Peel-Away 1 available
from Sherwin Williams paint dealers is a nonsolvent paint remover that can be used and is very
effective. It has a very high pH (alkaline) as it is made from sodium hydroxide. Follow the
package directions. This is safe to use on the steel but do not follow with the recommended acid
wash. Instead, rinse the steel very thoroughly with a hose after completing the procedure.
Drainage. If weep holes for drainage exist at the lower parts of forms, clear them of clogging by
carefully inserting a wire or stick into the holes. Report any clogged weep holes that cannot be
cleared.
Do not:
■ Do not wash with a pressure washer.
■ Do not clean with any product other than the solvents and paint strippers mentioned or with
2.6
Stainless steel
Indoors
plain water. Do not apply any coating whatsoever.
■ Do not use Prosoco maintenance products (1) without clearing their use with a supervisor, (2)
without testing, and (3) without prior experience in the use of the product. Prosoco products are
often very effective but can damage materials not specifically within their range of application.
Assume that art falls outside the range of application even though it may be made from the same
materials the Prosoco product was meant to treat.
■ Scratched graffiti requires the attention of a sculpture conservator. Do not sand or abrade to
blend in the scratches without permission from a supervisor.
Refer to “Four maintenance principles for all cases,” section 2.2
Understanding:
The following advice applies when a sculpture is composed totally or partially of stainless steel.
When it is a part of a sculpture, the particular restrictions and advice for adjacent or nearby
materials must be considered as well. Stainless steel is generally problem-free outdoors and should
have no problems at all indoors, but art made from stainless steel will accumulate dirt and marks,
and sometimes graffiti, which call for cyclic attention. Be aware that small rust like spots or
general orange stains of corrosion do form on stainless steel. Do not attempt to remove this
corrosion as it is not a problem. There are various finishes to stainless steel that call for some
specialized, periodic attention such as polishing and mild abrasive cleaning. Report concerns
about deteriorated original finishes but do not attempt to restore a finish without instructions
specific to the sculpture.
Cyclic actions:
Soiling. Periodically vacuum or wet-wipe away accumulated dust. It is safe to use detergents, even
all-purpose household cleaners, to remove grime. Always use cleaning agents sparingly and apply
to the cloth or paper towel. Do not spray directly on the sculpture.
Graffiti. Paint and pen graffiti, oil stains, and tar deposits can be removed from stainless steel, but
aggressive rubbing during removal process must be avoided so as not to burnish the metal. It is
important, however, to try to remove as much as possible since some graffiti seems to attract
more. Restrict your removal method to cloths and solvents. Solvents available from hardware
stores that would be effective include acetone and methyl ethyl ketone
(MEK). Thick applications
of paint can be removed using any of the solvent-based commercial paint strippers.
Do not:
■ Do not clean with any product other than the solvents mentioned or with plain water. Do not
apply any coating whatsoever.
2.6