Removing Bird Repellent Gels from Masonry

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.


  1. 01 SUMMARY
  1. This specification provides guidance on removing bird repellent gels from masonry and removing any residual stains left behind.
  2. One method of bird control involves the use of a toxic irritant gel, applied like caulk to horizontal surfaces where birds roost. One result is the presence of a gummy, oily residue which can attract dirt, stain masonry and soil occupants who come in contact with it.
  3. 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)


  1. Product Data:
    1. Protection Program: Prior to the execution of cleaning samples, submit to the RHPO a written description of the methods and materials for protection of all surrounding materials not to be cleaned.
    2. Waste Water Collection and Removal: Prior to execution of cleaning samples, submit to the RHPO a written description of methods of collection and removal of waste water and chemicals.
    3. Submit to the RHPO in triplicate a written description of the methods, materials, and equipment proposed for use in cleaning each type of masonry specified. Submit actual samples of each cleaning product to be used, along with manufacturer certifications that chemical ingredients conform to those specified for each cleaning procedure.
  2. Samples:
    1. Clean a representative sample of approximately 10 square feet of stone surface at locations selected by the RHPO, for each type of stone to be cleaned and each different procedure to be performed, including scraping to remove gel bulk. The samples accepted by the RHPO will be marked and left undisturbed to serve as standards for the entire job.
    2. Sample cleaning procedures must be executed in the presence of the RHPO and must demonstrate the Contractor's ability to perform each specified cleaning procedure without harming masonry. Damage to masonry as a result of cleaning operations may result in the technician's dismissal from the project.
    3. Adjust cleaning materials and methodologies during test panel cleaning as directed by the RHPO.
    4. Allow a minimum of seven calendar days after completing cleaning samples to permit the RHPO to study the sample panels for negative reactions.
    5. Do not proceed with cleaning until cleaning samples have been approved in writing by the RHPO.
    6. Approved samples shall be marked and left unaltered for the duration of the project. Approved samples shall be used as the standard for similar work throughout the project.
  3. Quality Control Submittals:
    1. Submit written program for each phase of restoration process including protection of surrounding materials on building during operations. Describe in detail materials, methods and equipment to be used for each phase of restoration work.
    2. If alternative methods and materials to those indicated are proposed for any phase of restoration work, provide written description, including evidence of successful use on other, comparable projects, and program of testing to demonstrate effectiveness for use on this project.


  1. Qualifications:
    1. General Objective: The objectives of stone cleaning are to remove bird repellent gel without damaging underlying material and to give the stone a clean uniform appearance. Protection of the stone from damage is the highest priority. Overly aggressive cleaning that damages or discolors the surface of the stone will not be accepted.
    2. Contractor Qualifications: This work must be done by a firm specializing in the cleaning of historic masonry. Refer to the Competency of Bidder Clause, Sections 00120 and 00900, for submission requirements.
    3. In the event that the Contractor wishes to modify any cleaning method specified, he must submit his proposal in writing to the RHPO for consideration. The RHPO may ask for test samples before approval. Approval or rejection of the Contractor's request will be at the RHPO's discretion. Any such changes shall be at no additional cost to the Government.
  2. Regulatory Requirements: Comply with municipal and Federal regulations governing cleaning, chemical waste disposal and scaffolding.


  1. Projects involving use of hazardous chemicals are subject to employee safety and environmental laws governing use and disposal of volatile organic compounds (VOCs). Specified products may not be permitted or appropriate for all locations. Products containing chemicals known to present health or environmental hazards should be used only as a last resort, where permissible, in accordance with manufacturer's directions and government requirements. Test milder formulations for effectiveness before proceeding to stronger alternatives.
  2. Cleaning or removal of stains from stone may involve the use of liquids, detergents or solvents which may run off on adjacent material, discolor the stone or drive the stains deeper into porous stones. Use the products and techniques described here only for the combinations of dirt/stain and stone specified.



A. ProSoCo, Inc.

Lawrence, KS 66117



  1. Cleaning Products:
    1. Repellent Gel Remover: Solvent-based, methylene chloride paint stripper formulated for removal of paint, tar, and adhesives from stone, such as "Sure Klean Heavy Duty Paint Stripper" (ProSoCo, Inc.), or approved equal.
    2. Oily Stain Remover: Solvent mixture of methylene chloride, ketone, methyl alcohol, and aromatic hydrocarbon, formulated for the removal of oily stains from stone, such as "Stand Off Oil & Grease Stain Remover" (ProSoCo, Inc.), or approved equal.
    3. NOTE: These products contain methylene chloride, a known carcinogen. Methylene chloride is banned in some states such as California. Regulatory information as well as alternative or equivalent chemicals may be requested from the Environmental Protection Agency (EPA) Regional Office and/or the State Office of Environmental Quality. Consult manufacturers regarding product substitutes appropriate for the particular application and conditions. Potential substitute products include: Commercial cleaner such as "ASPIR Solv Safe Solvent Cleaner" (Diedrich Technologies, Inc.), "Sure Klean Asphalt & Tar Remover" (ProSoCo, Inc.) or approved equal.
  2. Clean, potable water


  1. Gel Scraper (use for removal of gel residue only): Sharp steel blade, held at a shallow angle against surface to avoid damage to stone.
  2. Poultice Scraper: Non-metallic spatula.
  3. Brushes: Fiber bristle brushes (non-metallic).



  1. Protection: Following approval of proposed protection scheme as outlined in 1.02, install protection as follows:
    1. Take all precautions necessary to protect surrounding materials on the site, surfaces of the building not being cleaned, adjacent buildings, pedestrians and vehicles from coming in contact with cleaning chemicals, overspray, or runoff.
    2. Use polyethylene film, masking tape, and whatever means necessary to protect plantings, automobiles, building occupants, and building surfaces not being cleaned. Remove such coverings when masonry cleaning operations have been completed at that area of the building.
    3. Repair or replace with new stock, at no cost to the Government, to the RHPO's satisfaction, any materials or plantings damaged by scaffolding, laborers, cleaning materials, or cleaning operations.
    4. Prior to full scale cleaning, perform, in the presence of the RHPO, a site test of the protective methods to prove that chemical damage to stone, glass, interior finishes, and other surfaces not being cleaned will not occur.
    5. Test all drains and other water removal systems to assure that they are functioning properly prior to initiating cleaning operations. Notify the RHPO immediately of all blockages. Repair drains if so directed by the RHPO. Do not begin cleaning until drains are in working order.
    6. Provide a method to prevent solids such as stone or mortar residue from entering drains or drain lines. Clean out drains or drain lines that become blocked because of work performed under this Contract.
    7. Follow manufacturer instructions regarding the safe storage and use of all products and equipment. Remove all solvents, soiled rags, applicators, and other flammable materials daily and dispose off-site according to Federal and municipal regulations.
  2. Surface Preparation:
    1. Examine masonry to be cleaned prior to installing protection and executing sample panels. Notify RHPO immediately of any masonry damage observed. Use caution in installing protection and undertaking cleaning in damaged areas. Clean and rinse by gentlest means possible and follow RHPO's recommended precautions to avoid further damage to deteriorated masonry.
    2. Following approval of submitted materials and written description of methods as stipulated under 1.02 A, execute sample panels as directed in 1.02 B.


  1. Removal of Bird Repellent Gel:
    1. Remove bulk of gel by carefully scraping masonry surface with a steel blade.
      1. Hold blade at a shallow angle to avoid scratching or abrading stone surface.
      2. Scratching or otherwise damaging masonry will result in the cleaning technician's dismissal from the project.
  2. Apply and remove solvent paint/gel remover, as directed by manufacturer, as many times as necessary to remove surface coatings remaining after scraping bulk of repellent gel.
  3. Removal of Repellent Gel Stains:
    1. Follow manufacturer directions for using oily stain remover
    2. Allow product to dry thoroughly.
    3. Remove product by scraping with a nonmetallic spatula.
    4. Wash the surface thoroughly with clean, clear water.
    5. Repeat steps 1 through 4 as necessary to obtain results matching approved samples.