Cleaning and repolishing of interior historic marble

 Disclaimer

Technical procedures are supplied by GSA only as a reference. All procedures have been reviewed for general consistency with federal standards for rehabilitating historic buildings. 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 Description

1. This specification provides guidance for the cleaning and repolishing of interior historic marble.
   1. This specification has been developed for use on historic properties (defined as any district, site, building, structure, or object that is listed in or eligible for listing in the National Register of Historic Places) and provides an overview of accepted practices. Site-specific specifications, when appropriate, will be provided by the Architect.
   2. All work described herein, and related work must conform to the Secretary of the Interior’s Standards for the Treatment of Historic Properties.
   3. The Contractor shall provide all labor, material, equipment, and operations required to complete the rehabilitation work indicated herein.
   4. All work described herein, and related work must have the approval of a Cultural Resources Manager, Conservator, Historic Architect, or other professional who meets the standards outlined in the Secretary of the Interior’s Standards – Professional Qualifications Standards pursuant to 36 CFR.

1.02 Section includes

1. Cleaning of historic marble
   1. Marble cleaning
   2. General Cleaning
   3. Gel Cleaning
   4. Poultice Cleaning of Stains
   5. Repolishing

1.03 Related sections

1. Section 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections and should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from GSA Historic Preservation:
2. Safety Precautions
   1. Historic Structures Precautions
   2. Submittals
   3. Quality Assurance
   4. Delivery, Storage and Handling
   5. Project/Site Conditions
   6. Sequencing and Scheduling
   7. General Protection (Surface and Surrounding)

1.04 Quality assurance

1. The Contractor performing the work described in this Section shall have a minimum of five years experience in marble cleaning and restoration and shall have successfully completed at least three projects of similar scope within the previous five years. He/she shall demonstrate a working knowledge of The Secretary of the Interior’s Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring & Reconstructing Historic Buildings.
2. Field Supervisor Qualifications: Full-time supervisors experienced in historic treatment work similar in nature, material, design, and extent to that indicated for this Project. Supervisors shall be on Project site during times that historic treatment work is in progress. Supervisors shall not be changed during Project except for causes beyond the control of the specialist firm.
3. Worker Qualification: Persons who are experienced in historic treatment work of types they will be performing.

1.05 Submittals

1. The Contractor shall submit to the Architect, GSA Approving Official or GSA Historic Preservation:
   1. A detailed schedule of the areas to be cleaned and repolished, including an assessment of the problem surfaces, as well as proposed mockups and associated procedures, methods, products, and dwell times.
   2. Once cleaning and repolishing mockups are completed and approved by GSA Historic Preservation, Contractor shall submit proposed marble cleaning and repolishing procedures, application methods, dwell times, etc. for full scale project.
   3. The manufacturer’s product literature for all proprietary cleaning products. Product literature shall include specification data, Safety Data Sheets (SDS), and instructions for storage, handling, and use.
   4. A project safety plan to include at minimum: any personal protective equipment to be used by the contractor staff such as disposable clothing, gloves and safety glasses, procedures for emergencies and accidents, documentation of staff training in use of equipment and/or chemical products as required by the manufacturers.

1.06 Testing and mockups

1. Contractor, at inconspicuous locations designated by the Project Team and GSA Historic Preservation, shall perform small test patches (no larger than 6 inches by 6 inches) for all products to be used. Testing will determine the best method(s) to perform the work and ensure that the chosen products do not cause harm. The “best method” shall be defined as that which successfully cleans and repolishing the marble with no, or minimal, damage to the marble substrate.
2. Following testing, mockup panels shall be created (mockup panels may incorporate successful test patches) using the chosen methods. Size and location of mockup panels shall be determined by the project Team and GSA Historic Preservation.
3. The methods used, their application, etc. shall be in accordance with manufacturer’s instructions and shall duplicate those procedures proposed for the overall marble cleaning and repolishing process. The GSA Historic Preservation shall conduct a thorough evaluation of each method after stone cleaning and repolishing is complete, to determine the best method for the overall work.
4. The testing shall include an evaluation of the materials and techniques proposed for the protection of surrounding areas from the chemicals used to clean the stone. Evaluation must include the method to be used to collect any cleaning effluent.
5. Methods and materials for sealing cracks and openings prior to cleaning, shall be included in the mockups and approved by GSA Historic Preservation.
6. For proprietary cleaning systems, a representative of the cleaning materials manufacturer(s) shall be present during the preparation and execution of the test areas.
7. Approved test panel(s) shall become part of the work and shall serve as the quality standard for all similar work.
8. Any testing, demonstrations, or mockup that is rejected by the project team shall be removed in its entirety without damage to the surrounding masonry and a new demonstration/mockup shall be performed for the project team’s review.
9. Approval of mockups does not constitute approval of deviations from the contract documents unless GSA Historic Preservation, project manager, and contracting officer specifically approves such deviations in writing.

1.07 Delivery, storage, and handling (as applied to products and materials)

1. The Contractor shall:
   1. Deliver restoration cleaning and testing materials and proprietary products to the project site in manufacturer’s or distributor’s packaging, undamaged, complete with application instructions and Safety Data Sheets (SDS)
   2. Transport and store cleaning agents, chemicals, and solvents within the temperature range recommended by the manufacturer and away from direct sunlight. Handle all materials according to manufacturer’s instructions.
   3. All chemical products must be new and delivered to the site in labeled, unopened packaging.
   4. Collect and dispose of waste material, packaging, debris, and effluent associated with the marble cleaning work in accordance with local, state, and Federal environmental regulations.

1.08 Safety

1. The contractor shall only use chemical products whose safety data sheets (SDS) have been reviewed and considered acceptable by the Government. Any project surfaces containing lead-based paint, as disclosed by the Government, shall be handled by the contractor in accordance with OSHA (29 CFR 1926.62), EPA (40 CFR 261) and State regulations. Any lead-based paint or coating that is removed in a project resulting from this scope shall undergo Toxicity Characteristic Leaching Procedure (TCLP) testing by the contractor. The contractor shall dispose of any lead-paint waste as hazardous if it fails the TCLP.
2. Any paint or coating required to be removed which has not been disclosed by the Government to contain lead, shall be tested for lead by the contractor. All paints or coatings testing positive shall be handled and disposed of as lead-based.
3. The contractor shall isolate the work area with cones, tape or similar means as possible for the duration of the project, to prevent unauthorized individuals from entering the immediate work area.
4. For any work required on elevated surfaces (4 feet or more above the ground) the contractor shall install and use any ladders, scaffolding or platforms in accordance with OSHA regulations (29 CFR Subpart M).
5. Contractor and sub-contractor employees shall wear all required and appropriate PPE while on site.

1.09 Project/site conditions

1. The work of this Section shall be executed only when the air and surface temperatures are 40 degrees Fahrenheit and rising or less than 90 degrees F and falling. Minimum temperature for stone cleaning shall be 50 degrees F and above for at least two hours after completion and above freezing for at least 24 hours after completion.
2. The contractor is responsible for protecting existing adjacent areas and materials during the execution of the work and shall provide all necessary protection and follow all necessary work procedures to avoid damage to existing material assemblies not a part of the work of this Section.
3. At a minimum, the contractor shall:
   1. Protect woodwork, glass, and metal adjacent to stone areas to be cleaned, from overspray and possible chemical or water damage from cleaning operations. Cover all window openings with waterproof plastic to prevent leakage to the building exterior. Through cracks shall be sealed.
   2. If necessary, the contractor shall erect waterproof enclosures around areas where cleaning operations are in progress to protect nearby property and passers-by from overspray of cleaning chemicals or rinse water.
   3. The work area must be properly vented to the exterior to prevent the buildup of fumes in the area or the movement of the fumes to other occupied areas of the building.
4. If applicable, the contractor shall coordinate stone cleaning operations with the other trades involved in interior restoration work.
5. All contractor personnel performing stone cleaning operations shall be provided by the contractor with gloves, respirators, protective clothing and any other personal protective equipment (PPE) as recommended by the manufacturer of the marble cleaning products and required by local, state, and federal regulations.
6. The contractor shall complete installation of temporary sealants at window and door perimeters prior to starting cleaning operations where required to prevent leakage to the exterior.

1.10 Marble cleaning of soiling

1. Investigations and Method Selection
   1. Identification of material types, surface and substrate conditions, previous treatments, and the nature, cause and pattern of the soiling type for each area shall be determined. Testing may require additional technical expertise from a materials scientist, architectural conservator, microbiologist, and/or other technical expert. The Contractor shall choose the gentlest method possible to remove the soiling without damaging the substrate material.
   2. The Contractor shall conduct cleaning test patches, usually less than 6 inch by 6 inch, in unobtrusive locations on the marble to be cleaned. The purpose of the test patch is to determine the gentlest, most effective method to remove soiling from the stone. Several cleaning methods are generally tested side by side.
   3. The method of cleaning and the level of clean shall be approved by GSA Historic Preservation. The contractor shall protect adjacent materials, installed non-marble materials, and openings.
   4. Cleaning shall be undertaken through the mildest, least abrasive method as per testing.
2. Cleaning methods
   1. The gentlest cleaning methods should be tried first. The gentlest method for stone is water and soft bristle brushes.
   2. Water washing: Washing the surface with low jet pressure, not to exceed 100 pounds per square inch (psi), for water soluble dirt and chemical compounds, psi is to be determined during mockup with GSA Historic Preservation approval, lowest possible pressure will be used to achieve desired results. Optimal water pressure and wand distance are to be determined during execution of cleaning test patches. Note that most commercial pressure washing systems operate at significantly higher pressures than those recommended. Use of a pressure regulator to reduce pressures may be needed. All liquid must be contained and moved out of the building. Water volume used and containment measures shall be implemented in a manner that does not damage the subfloor or adjacent surfaces.
3. Definitions
   1. Detergents: Formulations made with dilutions of cleansers, surfactants, and chelating agents in water. pH Neutral or non-ionic detergents or surfactants are added to water for use on hydrophobic stains.
   2. Thixotropy materials: Materials that change from a gel to a liquid state when at rest and become fluid again when agitated.
   3. Surfactant: A substance, such as a detergent, that reduces surface tension when added to a liquid, thereby increasing the spreading and wetting abilities of that liquid.
   4. Stone Cleaners: Proprietary cleaning solutions containing detergents, acidic or alkaline compounds. If this type of product is proposed, great care must be exercised in product selection and preparation of test panels to identify potentially detrimental effects on the marble, grout, mortar, and surrounding surfaces. Raw acids and/or alkalis may not be used for marble cleaning.
   5. Poultices: A paste or slurry made with absorbent material or powder-inert clay, such as kaolin or sepiolite, diatomaceous earth (fuller’s earth); or Cellulose products such as pulp cellulose, shredded paper that is mixed with a cleaning solution (a liquid reagent such as water, organic solvent, among others).
   6. Marble polishing powder: A finely ground buffing powder manufactured specifically for restorative type polishing of polished marble surfaces, such as “#52-B Polishing Powder” (Eastern Marble) or approved equal. Or a prepared commercial polishing liquid or cream such as “Italian Craftsman” (Eastern Marble), or an approved equal.
4. Water used for cleaning of historic stone shall be potable and free of injurious amounts of oil, soluble salts, alkali, acids, and other impurities that might stain or otherwise damage stone, use of an in-line water filter may be necessary.

Part 2 – Products

2.01 Marble cleaning

1. MATERIALS
   1. Potable water
      1. Clean, potable water for cleaning and to remove chemical residue.
   2. Hot Water
      1. Heated to a temperature of 140 to 160 degrees Fahrenheit.
   3. Chemical Cleaner
      1. Off-the-shelf chemical marble cleaners as tested and approved or approved equivalent product.
      2. Chemical cleaner must be specifically formulated for the cleaning of polished or unpolished, as applicable, marble surfaces.
   4. Cleaning Compound
      1. Cleaning compound must be specifically formulated for use on the existing marble finish
      2. For the removal of built-up stains, use thixotropic alkali materials designed for cleaning marble surfaces.
   5. Poultice
      1. Poultice specifically formulated for use on marble incorporating surfactants and detergents
   6. Polishing agent
      1. Polishing agent must be specifically formulated for use on the existing marble finish. Polishing agent must not excessively abrade the surface of stone such that the stone requires resurfacing.
   7. Phenolphthalein or pH testing strips: Used to test pH of a surface after any chemical application during the work.
   8. Appropriate neutralizer as specified in marble cleaner product information.
2. Equipment for stone cleaning
   1. Pipes and hoses used for water cleaning shall be plastic or other similar material that is not subject to corrosion.
      1. Soft natural bristle brushes shall be used for scrubbing. Metal bristle brushes and brushes with metal ferrules are not to be used.
      2. Hoses, fittings, and equipment to be used for application of proprietary cleaning compounds shall be solvent, acid, or alkali-resistant as recommended by the manufacturer of the cleaning products.
      3. Buckets, trowels, and other tools, to be used for mixing, storing and application of poultices, shall be solvent-resistant plastic. Wood scrapers and trowels are permitted. No metal tools or containers are to be used.
   2. Water/rinsing method: Surfaces shall be rinsed with water after cleaning. Rinsing shall be undertaken until pH strips indicate that the rinse water and marble surface have been neutralized. Rinse water will be collected and disposed of in accordance with Federal, State, and Local environmental standards. Rates of water pressure should start at 100 psi or below and shall be no higher than 400 psi with minimal saturation, psi is as determined during mockup and approved by GSA Historic Preservation, lowest possible pressure will be used to achieve desired results.
   3. SURFACES MUST BE FULLY NEUTRALIZED FOLLOWING CLEANING. Contractor must test pH levels of marble to ensure neutralization.

2.02 Stone cleaning of stains

1. Contractor shall choose the gentlest method possible to remove the stain without damaging the substrate.
2. Contractor shall conduct stone cleaning test patches, no greater than 6 inches by 6 inches, in discrete locations, as determined by GSA Historic Preservation. The test patches will determine the gentlest, most successful method of removing the stains.
3. The method and level of “clean” shall be approved by GSA Historic Preservation.
4. Each cleaning method is to be performed in a manner that results in uniform coverage of all applicable surfaces, including any corners, moldings, and interstices, without streaking or damage to stone surfaces, mortar, or grout.

Part 3 – Execution

3.01 General

1. The cleaning test patches shall be performed by the Contractor and reviewed by GSA Historic Preservation, to determine the mildest successful cleaning method.
2. Contractor shall submit testing and cleaning schedules, including approved methods and materials.
3. Contractor shall protect all adjacent materials from chemicals and chemical runoff.
4. Runoff and waste from cleaning will be collected and treated according to local, state and Federal regulations, as applicable
5. Contractor shall remove and store light fixtures, and other appurtenances to ensure full access to stone surfaces, unless otherwise noted by the Architect or GSA Historic Preservation. Anchor holes and penetrations from appurtenances must be temporarily filled with removable sealant or protected with cover plates.

3.02 Marble cleaning

1. Surface Preparation for Cleaning
   1. Building shall be watertight prior to cleaning, through cracks and openings shall be sealed or covered, as used in the mockup and approved by GSA Historic Preservation.
   2. Prior to the start of cleaning, remove extraneous substances that are resistant to cleaning methods such as paint, caulking and wax.
      1. Remove paint and coatings with appropriate stripper. Follow all manufacturers instructions. Fully rinse and neutralize stone following stripping. Ensure surrounding areas are protected to prevent damage. If paint is being removed from an upper area, be sure to prewet the entire area below to prevent staining and damage.
      2. Caulk and applied products such as adhesive strips may be removed with water or razor blade. Care must be taken to ensure that the razor is held at an angle and does not scratch the marble surface.
2. Chemical Cleaning
   1. Stone surfaces are to be saturated with water prior to application of chemical cleaning products. Water should be applied starting at the bottom and working up.
   2. Cleaning of marble walls shall be performed from the bottom of the wall toward the top to ensure that dirty residues and rinse water will not wash over cleaned, dry surfaces.
   3. Contractor must contain and remove all water from the site. Water must not pond on the floor or run through the building. Water must be collected and disposed of in accordance with all local regulations. Plans for the collection and disposal of used water should be submitted and approved by GSA Historic Preservation prior to the start of the project.
   4. Manufacturer’s specifications shall be followed for all products used.
   5. Contractor shall use natural fiber brushes or very low-pressure spray (not to exceed 100 psi) for product application, psi is as determined during mockup and approved by GSA Historic Preservation, lowest possible pressure will be used to achieve desired results. High-pressure spray equipment shall not be used for the application of any cleaning product.
   6. Soft natural bristle brushes may be used to agitate the cleaning product.
   7. Following product dwell, loosened soiling shall be removed using a low-pressure water rinse or sponge rinsing. Do not allow the cleaning products to dry on stone surfaces, or to dwell beneath scaffolding or other access or temporary protection supports.
      1. Low-pressure water rinse surfaces from top to bottom using a 45 degree fan-tip nozzle with a nozzle pressure not to exceed 300 psi and a flow of approximately 4 gpm. Psi is as determined during mockup and approved by GSA Historic Preservation, lowest possible pressure will be used to achieve desired results. A minimum distance of 18 inches between the nozzle tip and the stone surface shall be maintained. Remove the waste water as work progresses by wet vacuum or other appropriate means. Do not allow water to pond on the floor. Dispose of water in accordance with all applicable regulations.
      2. Sponge rinse the surface thoroughly using fresh, clear water. Change the rinse water frequently.
   8. SURFACES MUST BE FULLY NEUTRALIZED FOLLOWING CLEANING. Contractor must test pH levels of stone to ensure neutralization.
   9. Following cleaning: Contractor shall remove all temporary protection and inspect all areas for cleaning related damage
3. Non acidic gel chemical cleaning
   1. Prewet stone with hot water applied by low-pressure spray not to exceed 100psi.
   2. Apply non acidic gel cleaner in ⅛-inch thickness by brushing, working into joints and crevices. Work in sections and apply quickly and cover area uniformly to ensure a uniform dwell time of entire area.
   3. Allow cleaner to remain on surface for the dwell time established during the mockup. Agitate if necessary. Do not allow the cleaner to dry on the surface. Cover with plastic, apply a new coat or remove immediately if drying occurs.
   4. Remove majority of cleaner with a plastic spatula, scraping cleaner into containers
   5. Rinse remaining cleaner off surface with cold water applied by low-pressure spray to remove chemicals and soil. Ensure that surface is neutralized.
   6. Repeat cleaning procedure, if necessary, to produce cleaning effect established by the mockup. Do not repeat procedure more than once without informing GSA Historic Preservation, unless specified.
4. Non acidic liquid chemical cleaning:
   1. Wet stone with hot water applied by low-pressure spray not to exceed 100psi.
      1. Apply cleaner to stone in two applications by soft bristle brush.
      2. Allow cleaner to remain on surface for period established by mockup.
   2. Rinse cleaner and soiling from stone with cold water applied by low-pressure spray, not to exceed 100psi. Ensure that surface is neutralized.
   3. Repeat cleaning procedure, if necessary, to produce cleaning effect established by the mockup. Do not repeat procedure more than once without informing GSA Historic Preservation, unless specified.
5. Poultice cleaning for heavy stains
   1. Clean dirt or dust, with a soft clean rag, from the surface to be treated prior to application of the poultice.
   2. prepare the cleaning poultice by mixing the liquid additive with the dry poultice to a thick creamy consistency.
   3. Pre-wet marble and apply a thick layer of poultice to the stained surface using a wood or plastic trowel.
   4. Cover the poultice with a plastic membrane and allow to dry 8 to 24 hours, depending on test samples.
   5. Scrape the poultice from the marble with a plastic or wooden implement and use a soft fiber bristle brush to scrub the surface with water.
   6. Rinse cleaner and soiling from stone with cold water applied by low-pressure spray, not to exceed 100psi. Ensure that surface is neutralized.
   7. Repeat cleaning procedure where required to produce effect established in mockup. Before repeating poulticing check area to ensure that overcleaning has not occurred and make sure poultice is applied to a large enough area that it won’t create ghosting. Do not repeat procedure more than once without informing GSA Historic Preservation, unless specified.
6. POLISHING/BUFFING TREATMENT
   1. Determine original finish of marble before proceeding with any repolishing procedure.
   2. Perform a mockup of the proposed polishing treatment in an appropriate, not highly visible area, to determine appropriate approach to repolishing the marble. Mockup must be approved by GSA Historic Preservation.
   3. Wet the surface with mineral water.
   4. Sprinkle the marble polishing powder over the surface.
   5. Dampen cloths with mineral water (if they are to be used).
   6. Rub the powder onto the stone with the damp cloths or by using a hand-held buffing machine in long, even strokes; keeping clear of adjoining vertical surfaces.
      NOTE: Apply polishing powder to marble surfaces to comply with manufacturer’s recommendations for hand application methods, unless otherwise indicated. Do not allow to remain on surface for periods longer than that indicated or recommended by manufacturer.
   7. Buff until a uniform polish, consistent with the historic design intent, is achieved.
      1. For most historic floors, the original finish is a honed (non-reflective) finish. Walls and vertical surface were often given a soft satin polish. Highly polished surfaces became more popular after World War II.
   8. Wipe clean with a damp cloth.
      -OR-
   9. For prepared liquid or cream polishing agents, follow the manufacturer’s recommended directions.

3.03 Final report

Contractor shall:

1. Provide a final report of completed work, including all approved submittals, mockups and photographs of the areas cleaned that were taken before, during, and after the work. Report shall also include:
   1. A written summary of the project
   2. Results upon final inspection and approval
   3. Discussion of steps taken or new findings not specified in the initial documentation
   4. Any applicable ongoing care and warranty requirements.

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.

Rewrite
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.