Architectural bronze
Outdoor copper alloy where the green is not dirt, cleaning will not restore it, and the wax afterwards is what the cleaning was for.
In detail
Bronze fixed outdoors — plaques, memorials, statuary — behaves differently from the indoor brass and silver this catalogue holds, because the corrosion is continuous and the weather is part of the system. The federal conservation procedure sets expectations before method: cleaning and waxing RETARD corrosion, the piece looks darker and less green afterwards, and the original appearance cannot be restored with wax. Restoration is a conservator's job, and so is anything involving a flame. The cleaning itself is unexpectedly gentle: dry soft-bristle brushes for loose dirt, then a scrub with water and a little non-ionic detergent using natural or plastic bristle brushes, rinsed until no effluent remains and dried by blotting rather than wiping. Two constraints concern the surroundings rather than the metal. The substrate beneath is flooded with clean water throughout, so effluent is not absorbed into the wall. And the water is itself a variable: de-ionised or distilled water is MORE aggressive than tap water and is preferred on the bronze, but must not be used where the plaque is mounted on polished stone, marble, limestone or concrete, because it can etch them.
Properties
Sensitivity
- Acids
- Recorded
- Alkalis
- Not known
- Chlorine bleach
- Not known
- Abrasion
- Recorded
- Porous
- Not applicable
“Not known” means CleaningHQ has not established this, not that the material is unaffected.
What works
Non-ionic detergent is safe on, in specific conditions, Architectural bronze
Safe only in specific conditions
This is only appropriate within specific limits. Outside those limits, CleaningHQ makes no claim.
Only within these limits:
- A SMALL amount in water, with natural or plastic bristle brushes
- Dry soft-bristle brushing first, to dislodge loose dirt and debris
- Rinse until no cleaning effluent remains, then dry thoroughly by blotting rather than wiping
- Keep the substrate beneath flooded with clean water throughout, so effluent is not absorbed into it
- A bright, dry, warm day, so water and solvent evaporate quickly
The expectation is set before the method: cleaning and waxing RETARD corrosion and cannot restore the original appearance. The piece will look darker and less green afterwards, not new.
Precautions
- Wear gloves
- Rinse thoroughly afterwards
Why we say this
Supported
A complete federal conservation procedure with every condition stated in the source. Nothing here is reasoned out.
Sources
Conserve O Gram 10/5: Caring for Outdoor Bronze Plaques, Part II — Cleaning and Waxing
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That the plaque is scrubbed with water and a small amount of a non-ionic detergent using natural or plastic bristle brushes, that dry brushing precedes it, that the surface is rinsed until no effluent remains and dried by blotting, that the substrate is kept flooded, and that the work is done on a bright dry warm day. (states this directly)
Verification: a person has read the passage relied on.
Read on — 'Introduction to Cleaning and Waxing', 'Preparation', 'Cleaning' and 'Waxing'. Supports the claim as stated. Supplies a complete outdoor metal cleaning system with required aftercare, and one fact with much wider reach than its subject: distilled water is more aggressive than tap water and etches carbonate stone.
Last reviewed by a person on .
Water is safe on, in specific conditions, Architectural bronze
Safe only in specific conditions
This is only appropriate within specific limits. Outside those limits, CleaningHQ makes no claim.
Only within these limits:
- De-ionised or distilled water is preferred ON THE BRONZE, because it is more aggressive
- NOT where the plaque is mounted on polished stone, marble, limestone or concrete — it can etch them
- Substrate beneath kept flooded with clean tap water throughout
The purity of the water is a variable rather than a detail, and it points in opposite directions for the metal and for what the metal is fixed to.
Why we say this
Supported
A clearance whose condition is about the surrounding material rather than the one being cleaned, which is unusual and is exactly what the source says.
Sources
Conserve O Gram 10/5: Caring for Outdoor Bronze Plaques, Part II — Cleaning and Waxing
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That de-ionised or distilled water is more aggressive for cleaning than tap water and is recommended for use on bronze plaques, and that it should not be used for cleaning plaques mounted on highly polished stone, marble, limestone or concrete as the water can cause slight surface etching. (states this directly)
Verification: a person has read the passage relied on.
Read on — 'Introduction to Cleaning and Waxing', 'Preparation', 'Cleaning' and 'Waxing'. Supports the claim as stated. Supplies a complete outdoor metal cleaning system with required aftercare, and one fact with much wider reach than its subject: distilled water is more aggressive than tap water and etches carbonate stone.
Last reviewed by a person on .
Why
- Architectural bronze is explained by Water purity and aggressiveness
Aftercare and prevention
- Non-ionic detergent requires the aftercare Architectural bronze
Wax once the surface is completely dry. On outdoor bronze the wax IS the corrosion barrier, so a cleaned unwaxed plaque is left more exposed than an uncleaned one.
Sources for this page
Sources
Conserve O Gram 10/5: Caring for Outdoor Bronze Plaques, Part II — Cleaning and Waxing
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That cleaning and waxing retard corrosion without restoring appearance, that the method is dry brushing then a scrub with water and a little non-ionic detergent, that the substrate is kept flooded to prevent effluent absorption, and that distilled water is more aggressive than tap water and can etch polished stone, marble, limestone or concrete. (states this directly)
Verification: a person has read the passage relied on.
Read on — 'Introduction to Cleaning and Waxing', 'Preparation', 'Cleaning' and 'Waxing'. Supports the claim as stated. Supplies a complete outdoor metal cleaning system with required aftercare, and one fact with much wider reach than its subject: distilled water is more aggressive than tap water and etches carbonate stone.
Last reviewed by a person on .