Methods of Bleaching Stains on Wood Floors

CSI Division
Division 9 - Finishes
Section
Wood Flooring
Last Modified

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.

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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.

PART 1–GENERAL

1.01 SUMMARY

  1. This procedure includes guidance on removing stains from wood floors using different methods of bleaching. These methods include using household chlorine bleach, oxalic acid, or a concentrate hydrogen peroxide solution.

  2. Read “General Project Guidelines” along with this specification. 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). The guidelines cover the following sections:

    1. Safety Precautions

    2. Historic Structures Precautions

    3. Submittals

    4. Quality Assurance

    5. Delivery, Storage and Handling

    6. Project/Site Conditions

    7. Sequencing and Scheduling

    8. General Protection (Surface and Surrounding)

PART 2–PRODUCTS

2.01 MATERIALS

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 (*).

  1. Denatured Alcohol:

    1. Other chemical or common names include Methylated spirit*.

    2. Potential hazards: TOXIC AND FLAMMABLE.

    3. Available from hardware store, paint store or printer’s supply distributor.

  2. Mineral Spirits:

    1. A petroleum distillate that is used especially as a paint or varnish thinner.

    2. Other chemical or common names include Benzine* (not Benzene); Naphtha*; Petroleum spirits*; Solvent naphtha*.

    3. Potential Hazards: TOXIC AND FLAMMABLE.

    4. Safety Precautions:

      1. AVOID REPEATED OR PROLONGED SKIN CONTACT.

      2. ALWAYS wear rubber gloves when handling mineral spirits.

      3. If any chemical is splashed onto the skin, wash immediately with soap and water.

    5. Available from construction specialties distributor, hardware store, paint store, or printer’s supply distributor.

  3. Chlorine Bleach:

    1. Other chemical or common names include Bleaching solution*; Household bleach*; Laundry bleach*; Sodium Hypochlorite*; Solution of chlorinated soda*.

    2. Potential Hazards: CORROSIVE TO FLESH.

    3. Available from chemical supply house, grocery store or supermarket, hardware store or janitorial supply distributor.

  4. Oxalic Acid (COOH)2 or (H2C2O4):

    1. A poisonous strong acid that occurs in various plants as oxalates and is used especially as a bleaching or cleaning agent and in making dyes.

    2. One of the strongest organic acids.

    3. Other chemical or common names include Dibasic acid; Ethanedioic acid; Acid of sugar*.

    4. Potential Hazards: TOXIC; CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS.

    5. Available from chemical supply house, dry cleaning supply distributor, drugstore or pharmaceutical supply distributor, hardware store, or photographic supply distributor (not camera shop). (Often sold under a manufacturer’s brand name; the chemical name may appear on the label.)

  5. Hydrogen Peroxide (H202): The concentrate solution used for wood bleaching - typically sold as a two-part kit containing sodium hydroxide.

    1. An unstable compound used especially as an oxidizing and bleaching agent, an antiseptic, and a propellant.

    2. Other chemical or common names include Peroxide of hydrogen*; Solution of hydrogen dioxide*; Superoxol*; (hydrogen peroxide is commonly sold as a 3% solution; Superoxol is a 30% solution; Superoxol causes flesh burns; 3% hydrogen peroxide does not). THIS PROCEDURE CALLS FOR USE OF THE 30% CONCENTRATION.

    3. Potential Hazards: TOXIC (when concentrated); CAUSTIC TO FLESH; FLAMMABLE (in high concentration).

    4. Available from chemical supply house, drugstore, pharmaceutical supply distributor, or hardware store.

  6. Clean, soft cloths.

  7. Clean, potable water.

2.02 EQUIPMENT

  1. Glass or porcelain container.

  2. Stiff bristle brushes.

  3. Sponges.

  4. Vacuum.

  5. Protective gloves.

PART 3–EXECUTION

3.01 PREPARATION

  1. Ensure that there is plenty of ventilation in the work space.

  2. Wear protective gloves at all times when working with bleach.

  3. Wash wood using denatured alcohol to remove any dirt or other impurities from the surface.

  4. Sand the wood and remove any paint or varnish. Brush and/or vacuum dust and debris from the surface.

  5. Remove any grease or oil from the surface by washing with mineral spirits and a clean, soft cloth.

3.02 ERECTION, INSTALLATION, APPLICATION

CAUTION: DO NOT MIX AMMONIA WITH CHLORINE BLEACHES. A TOXIC GAS WILL RESULT. DO NOT USE BLEACH ON BIRD DROPPINGS.

NOTE: TEST CLEAN A SMALL AREA BEFORE PROCEEDING WITH THE WORK TO DETERMINE THE BEST METHOD FOR REMOVING THE STAIN.

  1. Stain Removal Using Household Chlorine Bleach: Recommended for removing an aniline dye finish and ink stains from wood.

    1. Apply bleach to the stained area using a clean, soft cloth or stiff bristle brush. Use straight from the bottle; do not dilute.

    2. Allow to sit on the surface for at least 10 minutes; reapply if necessary.

    3. Thoroughly rinse the surface with clean, clear water.

    4. Allow to dry for at least 24 hours before refinishing.

  2. Stain Removal Using Oxalic Acid: Recommended for removing blue ink stains, iron stains and darkening or blackening of wood due to age or previous cleaning.

    1. Dissolve crystals in hot water in a glass or porcelain container. Use the the solution at a high concentration and while it is still warm.

    2. Apply the solution liberally to the surface using a clean, soft cloth or stiff bristle brush.

    3. Allow to sit on the surface for at least 10 minutes. It may take longer (up to an hour) to achieve effective results depending on the type of stain and type of wood; agitate with a stiff bristle brush if necessary to aid in stain removal; reapply if necessary.

    4. Thoroughly rinse the surface with clean, clear water.

    5. Allow to dry for at least 24 hours before refinishing.

  4. Stain Removal Using Concentrated Hydrogen Peroxide (30%): Recommended for lightening woods or as a last attempt at removing a stain before resorting to replacement.

  5. NOTE: HYDROGEN PEROXIDE AT THIS CONCENTRATE IS THE STRONGEST OF THE THREE BLEACHES LISTED. IT IS TYPICALLY SOLD AS A TWO-PART KIT CONTAINING SODIUM HYDROXIDE.

    1. Dampen the wood using a sponge soaked in clean, clear water.

    2. Apply mixture of hydrogen peroxide and sodium hydroxide uniformly over the surface. Follow manufacturer’s recommendations for application procedures and dwell time.

NOTE: BLEACHES TEND TO RAISE THE WOOD GRAIN WHEN APPLIED; THIS WILL REQUIRE SANDING UPON COMPLETION.

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Last updated: Aug 13, 2017
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