General Exterior Facade Chemical Cleaning Specifications
Paint Stripping & Graffiti Removal
As in other types of cleaning tasks, paint removal requires testing procedures and a strict adherence to manufacturer's recommendations.|
There are two basic types of paint removers, solvent and alkaline and their reaction with paint is slightly different. The solvent based paint remover (generally methylene chloride) reacts with the paint by dissolving the organics and causing the paint to swell and form a gel consistency. Alkaline base removers (sodium hydroxide or potassium hydroxide) chemically attack the vehicle in the paint by hydrolysis.
The objectives of a paint removal project will include 1. Exposing the natural beauty of the substrate. 2. Revealing all masonry areas requiring replacement, repair and repointing. 3. Leaving the surface physically and chemically compatible for the application of new paint, if desired. 4. Not causing physical or chemical damage to the substrate or to sound mortar joints.
The paint removal method utilized shall be a chemical treatment combined with a high pressure water spray. The type of paint removal method and material best suited to remove the paint is dependent upon the type and age of the paint layers and temperature conditions and shall be variably employed as needed at the contractors discretion, subject to conformance with other parts of the specifications.
Testing should include both a solvent base remover and an alkaline base remover. Depending on the type of paint on each layer the project may require one or the other or both types of removers.
A 100 square foot (30 m^) sample area shall be cleaned prior to the award of the contract. This sample, once accepted by the owner and the architect, shall serve as the standard of quality for the project.
When samples are required for testing, these samples shall be provided in the manufacturer's- original container with the manufacturer's original label which shall contain a description of the container's contents, recommended use and instructions for use, cautions and warnings and any additional safety labeling required for the use of the product.
Materials will be delivered in manufacturer's original, unopened, protective packaging that plainly show the designated product name, manufacturer's directions and name of manufacturer.
Store materials in a dry place off the ground and under cover to prevent damage and intrusion of water or foreign matter.
The contractor shall provide and erect safe and adequate scaffolding and equipment required for the proper execution of the work. All scaffolding shall be properly braced and erected to insure the safety of the workmen and meet all appropriate OSHA regulations.
The contractor shall take all necessary precautions for the protection of all property and the safety of the public. The Contractor shall provide, erect and maintain barricades, lights, danger signals, and warning signs as deemed appropriate by the architect. All specified requirements shall be in addition to all of the approved manufacturer's requirements or recommendations.
Surrounding areas shall be protected from contact with paint strippers, rinsing and overspray. The surrounding areas shall include, but shall not be limited to: all adjacent surfaces and structures- ; all private property including automobiles, outdoor furniture, etc: all animal life and their dwellings; all vegetation and plant life; and all other surfaces which would be adversely affected if placed in contact with the cleaning chemicals. The method and materials used for protection is subject to the approval of the architect.
Water rinsing shall be confined to the work area by controlling the drift of water and spray. Necessary screens, deflectors, tarpaulins and other protective measures shall be employed in order to confine the work and properly drain waste water.
All rinse water shall be clean, potable and free of materials injurious to mortar or substrate.
A viscous paint removal compound shall be applied by brush, spray or roller.
After standing on the surface for 30 minutes to 8 hours depending on the type of remover and the manufacturer, the effluent can be rinsed using 1500 PSI and 4 to 5 GPM (19 Litres/Min. at 103 BAR). Rinsing effectiveness can be increased by the use of hot water.
The pressure nozzle shall be held at a distance and angle from the substrate to prevent damaging the surface.
Paint removal shall commence at the bottom and shall continually progress up the face of the wall. Special care shall be taken during the paint removal operation in areas where the details may have deteriorated underneath the paint. Should any paint removal operation cause the slightest injury to the masonry or reveal extensive areas of deteriorated stone, stop work immediately and notify the Architect. Avoid water spray into large open cracks or open joints.
The surfaces shall be rinsed with clean water to remove all residue. The substrate shall be rinsed until the rinse water is neutral (pH7).
With some strong alkaline removers, it may be necessary to rinse with a mild acid to achieve substrate neutralization.
Repeat the procedure until the specified level of paint removal is attained.
Check all local and federal regulations on the disposal of paint wastes.
All of the above information applies to graffiti removal. Since there is no way to predetermine the type of paint on the surface, testing should be performed using an alkaline and a solvent base remover. Once the proper remover is determined, then conventional paint removal methods can be utilized. Several applications may be necessary to remove all traces of the paint.
After the paint has been removed, it may be necessary to clean the substrate with an appropriate cleaner to prevent "ghosting" which is the faint outline of the graffiti in the pores of the substrate.
The manufacturer has developed his cleaning systems to perform certain predetermined tasks. Any deviation from the prescribed methods and procedures may compromise the end results.