Removing Graffiti from Historic Masonry
- CSI Division:
- Division 4- Masonry
- Unit Masonry
- 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.
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
A. This specification provides guidance for removing graffiti from historic masonry materials.
- 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.
- All work described herein and related work must conform to the Secretary of the Interior’s Standards for the Treatment of Historic Properties.
- The Contractor shall provide all labor, material, equipment, and operations required to complete the rehabilitation work indicated herein.
- 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
A. Cleaning of graffiti from masonry surfaces
1.03 RELATED SECTIONS
A. 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 the Regional Historic Preservation Officer (RHPO).:
- Safety Precautions
- Historic Structures Precautions
- Quality Assurance
- Delivery, Storage and Handling
- Project/Site Conditions
- Sequencing and Scheduling
- General Protection (Surface and Surrounding)
1.04 QUALITY ASSURANCE
A. The Contractor performing the work described in this Section shall have a minimum of five (5) years experience in masonry 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.
A. The Contractor shall submit to the Architect or GSA Approving Official:
- A detailed schedule of the areas to be cleaned, including an assessment of the problem surfaces, and proposed graffiti removal procedures, application methods, dwell times, etc., for approval once cleaning test panels are completed and approved.
- 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.
- 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.
A. The Contractor, at inconspicuous locations designated by the Project Team and RHPO, shall prepare test panels using the appropriate cleaning methods, to determine the best method to remove graffiti. The "best method" shall be defined as that which successfully removes the graffiti with no, or minimal, damage to the masonry substrate.
B. Size of test panels shall be determined by the project Team and RHPO
C. The methods used, their application, etc. shall be in accordance with manufacturer's instructions and shall duplicate those procedures proposed for the overall graffiti removal process. The RHPO shall conduct a thorough evaluation of each method after graffiti removal is complete to determine the best method for the overall removal work.
D. The testing shall include an evaluation of the materials and techniques proposed for the protection of surrounding areas from the chemicals used to remove the graffiti. Evaluation must include an evaluation of the method to be used to collect the cleaning effluent.
E. For proprietary cleaning systems, a representative of the cleaning materials manufacturer(s) shall be present during the preparation and application of the test areas.
F. Approved test panels shall become part of the work and shall serve as the quality standard for all similar work.
1.07 DELIVERY, STORAGE, AND HANDLING (as applied to products and materials)
A. The Contractor shall:
- 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)
- 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.
- Collect and dispose of waste material, packaging, debris, and effluent associated with the graffiti removal work in accordance with local, state, and federal environmental regulations.
A. 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.
B. 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.
C. 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.
D. 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).
1.09 PROJECT / SITE CONDITIONS
A. 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 masonry 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. Work shall not commence when rain, snow, or below-freezing temperatures are expected within the next 24 hours. All surfaces shall be free of standing water, frost, and ice.
B. 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 and vegetation not a part of the work of this Section.
C. At a minimum, the Contractor shall:
- Protect woodwork, glass, and metal adjacent to masonry 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 interior.
- Protect surrounding vegetation from runoff during cleaning operations.
- Exterior graffiti removal work areas should be accessed from the exterior only. Under no circumstances are hoses to be run or equipment transported through the building during exterior graffiti removal operations.
- 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.
D. If applicable, the Contractor shall coordinate graffiti removal operations with the other trades involved in exterior and interior restoration work, including but not limited to masonry restoration, sealing, and painting. Masonry cleaning is to be completed prior to restoration of windows, doors, and metalwork, and prior to any exterior painting in the affected areas.
E. All Contractor personnel performing graffiti removal 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 masonry cleaning products and required by local, state, and federal regulations.
F. 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 interior.
PART 2 - PRODUCTS
2.01 MASONRY CLEANING OF GRAFFITI
A. Investigations and Method Selection:
- Identification of materials types, surface and substrate conditions, previous treatments, and the materials used to create the graffiti 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 graffiti without damaging the substrate material.
- The Contractor shall conduct cleaning test patches in unobtrusive locations on the surface to be cleaned. The purpose of the test patch is to determine the gentlest, most effective method to remove graffiti from the masonry. Several cleaning methods are preferably tested side by side in small patches, size and location to be determined by RHPO and the project team.
- Incised graffiti cannot be addressed by cleaning, and is therefore not covered under this section.
- If graffiti is being removed during a larger masonry cleaning operation, staining and graffiti should be addressed after atmospheric soiling and biological growth are removed.
- Graffiti is most easily removed when it has been freshly applied. Therefore, timely removal of graffiti is important.
B. Cleaning Methods:
- Water and Detergent: Washing the surface with water at low to medium jet pressure, 500 psi or less at 3-6 gpm. Neutral or non-ionic detergents may be introduced. 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. Use the lowest possible pressure to achieve the desired results and check substrate for possible damage.
- 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, or paint stripper among others).
- Organic Solvents and Paint Removers: Proprietary graffiti-removal products and/or commercial paint strippers containing organic solvents, sol gels, gel or paste removers, or paper or cloth-backed removers. Do not use “off-the-shelf” aerosol graffiti removers as these can cause additional staining and redistribution of pigments to clean areas.
C. Water/rinsing Method:
- Surfaces shall be rinsed with clean water after cleaning is completed. Rinse water shall be collected and disposed of in accordance with federal state, and local environmental standards. Rates of water pressure shall be no greater than 400 psi at 3-6 gpm with minimal saturation for hard masonry or concrete and no higher than 100 psi for soft masonry.
- Off-the-shelf chemical paint removers as tested and approved or approved equivalent product.
- Clean, potable water to remove chemical residue.
- Phenolphthalein or pH testing strips: Used to test pH of a surface after stripping paint with chemicals or any alkaline product.
- Appropriate neutralizer as specified in graffiti remover product information.
E. Equipment for Application:
- Pipes and hoses used for water cleaning shall be plastic or other similar material that is not subject to corrosion, which can cause discoloration and staining of surfaces being cleaned.
- Natural bristle brushes shall be used for scrubbing. Metal brushes are not to be used.
- 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.
- Buckets, trowels, and other tools to be used for mixing and application of poultices shall be solvent-resistant plastic. Wood scrapers and trowels are also permitted. No metal tools are to be used.
2.02 GRAFFITI REMOVAL
A. Apply the specified graffiti remover using a soft natural brush, roller or low pressure spray apparatus equipped with a nozzle 0.019 inch or larger. Spray equipment must be equipped with chemical resistant packing and hoses. Apply to a minimum thickness of 10 mils.
B. Allow the stripper to remain on the surface in accordance with the dwell time determined during preparation of the approved test panel. Dwell time will increase as temperatures decrease. Do not allow chemical to dry on substrate
C. Following dwell time the Contractor shall remove lifted layers using a squeegee, plastic scraper, or wet vacuum device as required. Collect paint and stripper residue, and dispose of in accordance with local, state and federal regulations.
D. Thoroughly rinse surface with clean water. Reapply stripper as required to remove all existing layers of graffiti.
E. After graffiti has been removed, but before masonry dries, apply appropriate neutralizer, as specified in Product Data Sheet. A neutral Ph (7 pH) should be achieved.
- Allow neutralizer to stand on wall about three minutes before rinsing. Do not allow neutralizer to dry on substrate.
- Thoroughly rinse the surface with clean, clear water.
- Test the pH with litmus paper or phenolphthalein:
a. Dissolve a 2" piece of phenolphthalein in denatured alcohol.
b. Brush the solution onto the surface. If it turns a shade from pink to magenta there is still chemical residue.
4. Continue to neutralize the surface and test until there is no color change in the phenolphthalein solution or the litmus paper registers as neutral.
2.03 FINAL REPORT
A. The Contractor shall:
- Provide a final report of completed work, including all approved submittals and photographs of the areas cleaned that were taken before, during, and after the work.
- Provide a written summary of the project and results upon final inspection and approval. The summary shall include a discussion of steps taken or new findings not specified in the initial documentation. Summary should also include any applicable ongoing care and warranty requirements.
END OF SECTION