Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
A. This procedure includes guidance on cleaning exterior copper architectural elements that are dirty, soiled, or discolored.
B. See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- General Protection (Surface and Surrounding)
These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO).
C. For additional information on the characteristics, uses and problems associated with copper, see 05015-01-S.
1.02 SYSTEM DESCRIPTION
A. Ornamental elements of copper are formed of very thin copper sheets. They should be in good condition, without any signs of surface dirt, debris, soiling, or discoloration.
NOTE: Chemical products are sometimes sold under a common name. This usually means that the substance is not as pure as the same chemical sold under its chemical name. The grade of purity of common name substances, however, is usually adequate for stain removal work, and these products should be purchased when available, as they tend to be less expensive. Common names are indicated below by an asterisk (*).
A. Copper Sulfate (CuSO45H20):
- A sulfate of copper especially the normal sulfate that is white in the anhydrous form but blue in the crystalline hydrous form and that is often used as an algicide and fungicide.
- Other chemical or common names include Cupric Sulfate; Blue stone*; Blue vitriol*; Roman vitriol*.
- Potential Hazards: TOXIC.
- Available from chemical supply house, drugstore or pharmaceutical supply distributor, garden and lawn supply center, hardware store, swimming pool supply distributor, or water and sanitation supply
B. Nitric Acid (HNO3):
- A corrosive liquid inorganic acid used especially as an oxidizing agent, in nitrations, and in making organic compounds such as fertilizers, explosives and dyes.
- Potential Hazards: CORROSIVE TO FLESH; CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS.
- Available from chemical supply house or hardware store.
C. Clean, potable water
A. Cellulose sponge mop or similar applicator
B. Clean soft wiping cloths
C. Heavy gloves and protective gear
A. Mix 4 ounces of copper sulfate, 1/2 gallon of lukewarm water and 1/8 ounce of nitric acid
NOTE: ABRASIVE AGENTS ARE NOT TO BE USE.
B. Apply the solution to the copper surface using a cellulose sponge mop or similar hand applicator.
CAUTION: AVOID APPLYING CLEANING SOLUTION TO METAL IN DIRECT SUN, AS IT BECOMES VERY HOT, AND THE DETERGENT OR SOAP SOLUTION WILL DRY IN STREAKS BEFORE IT IS POSSIBLE TO RINSE IT OFF. THESE STREAKS CAN VERY EASILY BECOME PERMANENT AND CANNOT BE REMOVED WITHOUT ABRASION.
C. Thoroughly rinse the surface with clean, clear water and dry with clean, soft cloths. Repeat the process as required to achieve the desired level of cleanliness.