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.
The following standard was developed from information produced by The Aluminum Association in their publication "Care of Aluminum".
Aluminum Cleaners May Be Classified Into Five Groups: (Listed from gentle to severe)
- Mild soaps, detergents. and non-etching cleaners
- Solvent and emulsion cleaners
- Abrasive cleaners
- Etching cleaners
- Special duty cleaners
NOTE: The gentlest methods of cleaning should be used first. If these are not effective, incrementally more aggressive methods may be used with caution under the supervision of a qualified architectural materials conservator
Mild Soaps, Detergents, And Non-Etching Cleaners
- May be applied with bare hands.
- Spot test strong detergents.
- Non-etching cleaners are alkaline or acid-based formulations mixed with inhibitors, which permit the cleaners to remove soil without attacking the metal or its finish.
- Nature and strength of chemical and length of application will vary from cleaner to cleaner.
- Use with a long-handled fiber brush and rubber gloves.
- After cleaning, thoroughly wash aluminum with clean, clear water and dry.
Solvent And Emulsion Cleaners
- Mild in action, but more effective in removing dirt and stains than milder cleaners.
- Effective in removing surface dirt and some stains, but NOT very effective in removing heavy dirt encrustations.
- May be used on bare, anodized, conversion-coated and porcelainized aluminum.
- The surface must be thoroughly rinsed and wiped dry to prevent water-spot staining.
- Spot test these cleaners on painted and lacquered finishes. An inappropriate solvent of solvent-containing emulsion can remove many paints and clear organic coatings (lacquers) used with aluminum.
- USE WITH CAUTION
- Range from moderate to heavy-duty depending on how coarse of an abrasive is used.
- Can remove most dirt, staining and corrosion from aluminum.
- Some generic descriptions of these cleaners include polish, cleaner, cleaner-polish, wax-cleaner, wax-polish, metal brightener and scouring powder.
- Abrasive cleaners contain abrasives to which water, oil, wax, silicones, soap and an acid or alkali may be added, either singly or in combination. The abrasives cut away the dirt and surface oxidation while the soaps, acids and/or alkalies clean, leaving traces of the wax, oil or silicones behind to provide luster and a small measure of surface protection.
- Abrasive cleaners containing fine grit or polishing agents may be used with care on all aluminum finishes. Cleaners containing moderately coarse grit may be used ONLY on porcelain finishes.
- Avoid prolonged rubbing with abrasive cleaners. This may dull a bright, specular finish.
- Apply abrasive cleaner-polish to a clean cloth and rub over the soiled area. Follow by polishing with a clean, dry cloth.
- DO NOT use a cleaner-polish on aluminum surfaces to receive an organic coating. Cleaner-polishes protect the aluminum surface by leaving a thin wax, or wax-like coating on the surface. This coating will prevent subsequent layers of paint or lacquer from adhering to the aluminum surface.
- These types of cleaners are often used to remove heavy soils and oxides prior to final cleaning and polishing with a fine-grit cleaner.
- Thoroughly remove abrasive cleaner before applying polish to avoid scratching the surface.
- On bare aluminum, moderate abrasives produce a finely scratched, light grey surface. The scratches are easily blended into a matte or satin finish by working the abrasive with the grain of the metal.
- Abrasive cleaners may be supplemented with a fine abrasive such as pumice or fine stainless steel wool (0000 to 00) or an abrasive nylon pad. DO NOT USE REGULAR STEEL WOOL. IT MAY LEAVE BEHIND RUST STAINS.
- Coarse abrasive cleaners are sometimes used to prepare anodized surfaces for painting. Apply light pressure ONLY to avoid deep scratches, which may be visible through the paint.
- DO NOT allow chemical-based cleaners to remain on bare or anodized aluminum too long. They may etch the surface finish of bare aluminum; white blemishes may develop on anodized aluminum.
- USE WITH CAUTION AND ONLY ON BARE ALUMINUM THAT IS HEAVILY CORRODED OR STAINED.
- APPLY WITH CAUTION; these cleaners remove small quantities of metal each time they are used; they MUST be rinsed thoroughly and neutralized.
- Not normally used on painted, plated, anodized or conversion coatings.
- For proprietary etching cleaner formulations, follow manufacturer's directions. A general procedure is as follows:
- Prepare the mixture and apply it carefully with a sponge or brush to an area no larger than can be kept wet.
- Allow cleaner to remain in place for the recommended time; rinse the surface thoroughly with clean, clear water.
- In general, cleaning should be performed from the bottom up. Etchant drips on uncleaned aluminum are more difficult to remove than drips on already cleaned aluminum.
- Etching cleaners may be supplemented by using a fine abrasive
- such as pumice or fine stainless steel wool (0000 to 00) or an abrasive nylon pad. DO NOT USE REGULAR STEEL WOOL WITH THESE CLEANERS. IT MAY LEAVE BEHIND RUST STAINS.
- Before applying a water-based etchant cleaner, the metal should be grease-free. When cleaning, rub all areas equally and/or soak areas for similar lengths of time.
- Hot water may be used for final rinsing to increase the drying speed of smaller aluminum products. Small parts may be rinsed in methyl alcohol and water
Special Duty Cleaners:
- USE WITH CAUTION AND ONLY BY AN EXPERIENCED PROFESSIONAL.
- These types of cleaners may require the use of steam, rotary wire-brushes and/or abrasive blasting.
- Pure steam is most suitable for use on bare, plated and porcelain aluminum finishes.
- DO NOT hold steam jets too close or too long against painted, anodized or conversion-coated blush or craze.
- Margot Gayle, David Look, John Waite. Metals in America's Historic Buildings. Washington,DC: National Park Service, 1995
- L. William Zahner. Architectural Metals. New York: John Wiley & Sons, 1995.