Taken from Hal’s secrets and GSA (Government Services Administration)
This maintenance guide is designed to protect and preserve your art using safe to repeat as cyclic maintenance. The work requires minimal training and is cost effective. These scheduled efforts can be done frequently or at least annually. If in doubt, consult a conservator especially if special situations arise. Occasionally, the best procedure is to do nothing, but it is always a good idea to record the condition, which will act as a reminder.
for all sculptures in all situations:
- Watch for an unusual situations and when found seek advice from a conservator or other knowledgeable person. Often, the curator of a local gallery or museum can assist or direct you to appropriate help.
- Use Common Sense: if something tells you an action might be harmful or cause an effect of which you are unsure, then seek advice or simply do nothing at this time, but note the condition and schedule a review.
- Proceed Gradually: perform a small initial inconspicuous test.
- Record the condition before working: this record will serve as a record for the artwork.
1.3 Maintenance cycle
Remove accumulated dust, bird droppings, salts, garden chemical overspray, or any material not part of the original sculpture. Forceful hose water washing is safe and desired as rain alone is ineffective. IF THERE ARE BROKEN WELDS OR OTHER SIGNS OF PHYSICAL WEAKNESS, then it should not be used [again observe before any maintenance]. Wash from top to bottom. Washing can be weekly if necessary, but at least once a year. Frequency is dependent upon the rate of soiling.
Remove dust with soft brushes or a soft bristle vacuum attachment.
Paint and Pen graffiti is important to remove as quickly as possible; graffiti seems to only attract more graffiti. Restrict your efforts to cloths and solvents. Different sculpture materials [weathering steel, steel, stainless steel, bronze, copper, stone, and concrete] all have preferred methods and solvents. These will be discussed under specific care procedures.
Look for drainage holes created by the artist. These are usually in the lower parts of the art and need to be cleared of clogging. Insert a wire is best, as stick can break. Record uncleared weep holes, and set a plan to clear them, at least record the condition for the future review.
2.0 Guidelines for Specific, Individual Materials
Note: when an artist has multiple materials, or the sculpture is on a plinth of different material, or near other materials [such as a bronze sculpture mounted on a stone wall], then recognise and consider these different materials and their procedures.
2.1 Weathering steel (Corten)
Corten was a favourite material for Pastorius’ Sculptures, when left exposed to air, the corrosion , which looks like rust, actually builds to a protective layer that prevents further corrosion. Corten is one brand of weathering steel, but the brand is so strong that almost all weathering steel is referred to by the one word. Thus, corten is often left uncoated to purposely corrode.
One of Hals’ earliest series was a set of mushrooms. As these mushrooms (one nearly 4 feet tall) were left outside to develop a patina, he duly watered them to speed the rust formation. His neighbour while witnessing this daily activity, cautiously advised Hal that she did not think watering the metal mushrooms would make them grow. Hal continued watering them anyway, as the coating which looks like rust, can actually be identified by its darker colour, and by a purple colour in some of its corrosion.
When this protective coating is disturbed, by scrapes, the process continues and will begin to “heal” itself.
If constantly exposed to moisture, such as near the ground, in shade, or where water puddles, the corrosion activity is more aggressive than rust on common steel and can weaken the sculpture significantly.
Indoor corten sculptures require care to protect the stable corrosion as it forms best in outdoor environments.
Follow the general outdoor and indoor routine guidelines. [see 1.3.1] Attention needs to be paid to sculptures placed near plantings which will be watered as the exposure to excessive moisture will accelerate the rusting process and can lead to structural damage. Carefully consider the placement of plants both indoor and outdoor in relation to the sculpture. Plant care must consider active drainage for the sculpture and the surface on which the sculpture rests. Weathering steel is sometimes painted. Paint can hold moisture in place against the steel and can create the damaging corrosive environment just mentioned. Likewise sculpture positioned next to walkways which are water cleaned may cause excessive water exposure thus corrosion.
Outdoors, care must be taken to remove bird droppings as quickly as possible due to the acidic moisture.
Paint, pen, oil, and tar are difficult due to these media penetrating into the corrosive layer. Removal as much as possible is still important due to the tendency of graffiti attracting more graffiti. Outdoor sculptures are more at risk to graffiti than indoor sculptures
- restrict removal method to cloths and solvents
- Use knit fabric instead of woven or terry cloth [course corrosion collects fibers]
- Solvents: Acetone /or MEK = methyl ethyl ketone. Solvents will dilute graffiti paint causing deeper penetration into some corrosion
- Thick paint applications can be removed using solvent based paint strippers [Sherman Williams “Peel-Away” is a non-solvent very effective paint remover, high pH = alkaline, FOLLOW DIRECTIONS, BUT DO NOT NEUTRALISE WITH ACID WASH, instead rinse thoroughly with water.
- Scratched graffiti should be left alone to form a new protective corrosion layer.
2.4 Corten precautions
- Look for loose flaky corrosion [“pack-out”]; a sign of continual excessive moisture.
- Drain holes must be checked and cleared.
- DO NOT WASH WITH A PRESSURE WASHER.
- DO NOT sand, brush, or abrade the protective corrosion [patina] unless to resolve a specific problem after appropriate consultation.
- Only use solvents listed for treating Graffiti or plain water
- Do not use Prosoco maintenance products:
- without clearing their use with a supervisor
- without testing, and
- 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 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
- Indoor corten may darken if solvents are used [it is best to treat the whole sculpture if specific areas need to be treated to create an even overall result.
3.0 Painted Steel
3.1 Understanding painted steel (generally painted corten):
Most painted outdoor sculptures are made from weathering steel, or sometimes aluminum, steel, and even 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.
Differences in coatings are significant when solvents are needed to remove graffiti. Only a very few coatings can withstand solvents.
3.2 Dealing with soiling
Use the same guidelines as with 1.3.1 basic guidelines with soiling and keep drainage clear and open.
Paint and pen graffiti, oil stains, and tar deposits can only sometimes be removed from painted metal as necessary solvents usually dull the paint coatings. Do not attempt to remove graffiti. Have a trained conservator perform this work. It is almost always safe to use mineral spirits and naphtha to remove some materials. Test these solvents in an inconspicuous place first.
- It is very important to inspect for coating loss that exposes steel
- Paint loss on aluminium may be ignored or treated as if steel, but do not use rust converters on aluminium.
- For other metals, if the area is small, use a rust converter [available at auto supply stores]. After the rust converter is dry, apply alkyd paint in a similar colour, keeping the new paint confined to the area of loss. “Rustoleum” is a good choice when there is no risk of the public touching the repair, since it takes a long time to dry. Drying time relates to its effectiveness in corrosion control. When these simple mends accumulate and become unsightly, consult with a conservator as overcoating orrecoating is needed and an expert should be consulted.
- Do not Pressure wash
- Do not use graffiti removal products, Naval Jelly, or even household cleaners
- Do not use solvents other than Mineral spirits pr Naphtha
- Do not use Prosoco products without a conservator consultation. See prosoco 2.4.6
- Watch for corrosion that creeps under coating and between joins of metal
- Also Watch for blistering paint
4.0 Bare Mild Steel
4.1 Understanding Bare Mild Steel
This low carbon industrial steel is often used by artists with specific intent to allow the surface to rust. Occasionally an artist will apply an oil coating in an attempt to slow or stabilise the corrosion patina. Unfortunately this normally results in a degraded, darkened pealing film.
Follow the basic routine maintenance [paragraph 1.3.1], with the exception that frequency should be monthly not weekly. Again, frequency is directly proportional to the rate of soiling accumulation.
Follow the same guidelines as for Corten, with knit cloth, same solvents. Rubbing with solvent soaked cloth will remove loose corrosion which is acceptable as the higher priority is Graffiti removal.
4.4 Bare Mild Steel precautions:
- Do not use water or paint removers that need water for rinsing as this may activate localised corrosion.
- Do not sand, brush, or abrade corrosion unless consultant directs for a specific problem.
- Use only solvents listed in 2.3.
- Pay attention to placement of art and wetting risks.
5.1 Understand Aluminium
Aluminium forms a stable white corrosion or light grey corrosion outdoors, which is usually a thin powdery film. This thin white corrosion and the normal small pits in aluminium are normal, and usually not problematic. However, damaging corrosion can corrode aluminium into a weak, expanded and flaky sheet, especially near ground contact or in salt environments.
follow the basic instructions in 1.3.1 with the exception of washing monthly rather than weekly. On indoor sculptures, for greasy marks, follow solvent treatments under the “graffiti care”.
follow the corten guidelines 2.3 with the exception Stop if the aluminium begins to discolour or gloss, and allow the solvents, strippers, or water to do nearly all the work
5.4 Aluminium precautions
- Do not Pressure wash
- Do not use commercial aluminium cleaners
- Do not use non-solvent paint strippers
6.0 Stainless Steel
6.1 Understanding Stainless Steel
Art made from stainless steel is generally problem free, but will accumulate dirt, marks, and if outdoors sometimes graffiti, which all call for periodic 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 specialised, periodic attention such as polishing and mild abrasive cleaning. Seek advice about deteriorated original finishes but do not attempt to restore a finish without expert instructions.
follow basic maintenance for soiling; see 1.3.1 with outdoor washing cannot be overdone. Indoor cleaning: periodically vacuum or wet-wipe away accumulated dust. It is safe to use 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.
use the procedures listed in 2.3 Solvents and cloths, while heavy deposits can use solvent and well as non-solvent paint removers. 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 solvent and non-solvent based commercial paint strippers.
6.4 Precautions with Stanless steel
- Do not use Prosoco products without expert advice. see 2.4.6
- Do not clean with any product other than the solvents mentioned or with plain water.
- Scratched graffiti requires the attention of a sculpture conservator. Do not sand or abrade to blend in the scratches without expert advice.
7.0 Bronze and Copper
7.1 With Bronze or Copper
Especially when part of a sculpture, the particular restrictions and advice for adjacent or nearby materials must be considered as well. Sculpture made from bronze or copper may or may not have an original surface. Some artists desire a specific patina colour; others want the metal to corrode as at will. Maintenance, should strive to maintain the existing appearance as long as possible or until the surface needs correction by a conservator. Wax is often used as a protective layer, once applied, must receive annual reapplications. If free of any old coating, then no maintenance coating should be applied until an evaluation by a conservator. Some sculptures may be coated with a clear resin (Incralac), deteriorated it is white or hazy and may flake or peel from the bronze, or yellowish and peeling. It is safe to apply or reapply wax over Incralac.
Follow general instructions [1.3.1] but, use wet cloths or sponges to wash off stubborn bird droppings with care not to rub through a coating or remove green or black patina. Everything else applies. Then maintain the coating after the thorough wash by renewing the wax coating once a year with paste wax. In some situations, a sculpture can go for two or more years without waxing, but this cannot be predicted beforehand. So, once a year suits all bronze/copper sculptures. However, if there is no signs of a previous application of wax, then consult a conservator to evaluates the intent of the artist. It is recommended to use Butchers White Diamond clear paste wax as if waxing a car. White Diamond Clear paste wax is available from Shields Packaging (509-949-0900) or may be available at local hardware stores. Apply sparingly from the can using a natural bristle brush with the ferrule taped to prevent banging the bronze, work into the surface, spread any excess, and allow the wax to dry. Heavily textured surfaces require extra diligence to thin wax in crevices. A traditional, soft shoe-shine brush is an excellent tool for buffing the surface and is still easy to find. Otherwise, buff lightly with soft cotton cloths.
Indoor environment protected sculptures made of bronze, brass, or copper [unlike those found outdoors] usually retain the desirable or original patina that must not be altered or damaged in any way. So, Periodic removal of dust can be done by careful brushing with a soft brush as needed— not likely to be more often than once a year for indoor protected art.
Only in cases where no clear resin Incralac coatings are present can graffiti be safely removed. Solvents such as mineral spirits and naphtha will affect wax more than acetone and methyl ethyl ketone (MEK). Attempt the removal of paint graffiti with acetone and methyl ethyl ketone first using solvent soaked cloths. If a residue remains, use naphtha or mineral spirits to slightly dissolve the wax coating that is under the graffiti. Restore the wax coating after graffiti removal following the procedures for wax maintenance renewal described above.
Indoor graffiti does not usually occur, but should it happen an art conservator should be contacted.
7.4 Precautions for Brass and Copper
- Do not use Brasso, Ajax, or any other commercial cleaning product
- Do not use graffiti-removal products
- Do not use solvents to remove graffiti if a clear coating such as Incralac is known to exist on the bronze/copper sculpture
- Do not apply protective coatings other than renewal applications of specified wax.
8.0 Stone Sculpture and Bases
8.1 Understanding Stone properties
a sculpture or base composed totally or partially of stone is usually limestone, granite, and sometimes marble. Repeated washings help to keep stone clean and prevent stains from becoming permanent. Rain is often acidic so freshwater rinsing is beneficial to help neutralise the stone surface. Stone sculptures with mortar joints are damaged by biological growths such as lichen, so joints must be kept clean.
follow the basics advice at 1.3.3 with the weekly wash becoming a monthly wash, but should be performed at least once a year, as always the frequency depends on the rate of soiling. Whether the mortar joints are caulked or mortar, if there is lost of either do not refill without getting advice, as sometimes it is better to leave the joint open than improperly fill the space.
Indoor stone sculptures need to be dusted with a soft brush, as needed, at least annually.
Attempting to dissolve paint and other materials with solvents dilutes the material and allows it to soak into the stone. Therefore, do not attempt to remove graffiti from stone without first consulting with a sculpture conservator.
8.4 Precautions with Stone;
- Do not wash stone with a pressure washer outdoors, indoors do not wash with water or any other liquid.
- Do not scrub stone.
- Do not use any coatings on stone.
- Do not use Prosoco maintenance products see 2.4.6
- Scratched graffiti should have the attention of a sculpture conservator. Without advice, do not sand or abrade to blend in the scratches without permission from a supervisor. It is usually best to just be left alone.
- Watch for: Loose parts of stone sculpture
9.0 Wood Sculptures
9.1 Understanding wood sculpture
Outdoor and indoor wood sculptures may or may not be coated: if coated (including paint) the materials may vary, thus, it is not possible to recommend protective maintenance for all wooden sculptures. Indoor wooden art benefits from dust removal with a soft brush as often as needed.
Remove trash, dirt, leaves by brushing or vacuum, as water will often be absorbed or held by the wood. However, wood that has been coated should have that coating maintained, often annually. If it can be ascertained, treat annually the art as the artist treated the wood originally [re-apply if wax or oiled using the same product], if painted keep the painted surfaces clean and if waxed then wax annually.
Unfortunately, graffiti, oil, and tar deposits are extremely difficult to remove from wood, professional consultation is required in most cases.
- Do Not wash wood with water or solvents without expert advice
- Do Not apply coatings unless directed by an expert
- Do watch for Boring insects and seek advice if found
- Do watch for biological deterioration of wood and again seek advice. Prompt advice is always best.
10.0 Ceramic and Glass
These materials are usually durable to water and solvents and cleaning periodically is likely to be the extent of necessary cyclic maintenance. Be mindful of non-ceramic or non-glass materials used nearby or on the ceramic or glass. Indoor glass and ceramic material may be complex and sensitive so be gentle and test an inconspicuous area first.
Follow general guidelines [1.3.1] but if there is physical weakness as in loose, broken or cracked tiles/glass [similiar to weakness in metal sculptures] is it not safe to use a stream of hose water nor pressure wash a weakened sculpture. Sponges and cloths may be used to loosen soils. A detergent may safely be used and commercial glass cleaners may be used. Do not use tile or tub cleaners meant for household films as these do not occur on sculpture outdoors and these cleaners sometimes contain abrasives. Use only water unless absolutely necessary. Biological growths on tile grouts can be killed and discoloured with household chlorine bleach diluted one cup per gallon of water and applied repeatedly, then rinsed with clear water. Any loose gout should be promptly repaired by a person skilled, such as a tile contractor.
Indoor art should be dusted with a soft brush or wiped with a soft cloth. Stubborn dirt or finger marks can be removed with class cleaner. It is best to spray the cloth and then wipe the art.
Paint and pen graffiti, oil stains, and tar deposits can often be removed from glass and ceramics. It is almost always safe to use mineral spirits and naphtha to remove some materials and acetone or methyl ethyl ketone (MEK) for removing paints. Commercial paint strippers may also be safely used. Test these solvents in an inconspicuous place first.
Indoor sculptures may have sensitivities such that a conservator may need to be consulted.