Patented Dry System for Building Cleaning
	FACADE GOMMAGE AND ITS APPLICATIONS BY THOMANN-HANRY CLEANING CONTRACTORS

I. Profile - Thomann-Hanry Company

Thomann-Hanry provides exterior and interior masonry preservation services to clients in Europe and North America. Bernard Thomann, with thirty years of experience in the field of masonry preservation, has continued the direction of this family-run company which was founded in 1946. Headquartered in Paris, this French company has branch offices in Amsterdam, Brussels, Geneva, Lisbon, Luxembourg, Madrid, Milan, and most recently, New York City (USA), and Montreal (Canada). The firm also has a factory in Uzes, France where most of its specialized site equipment is designed and manufactured.

Although Thomann-Hanry employs specialists in stone replacement, repointing, consolidation, and waterproofing, the firm is most noted for its application of a cleaning method called Facade Gommage. It was first developed by founder Robert Thomann in 1965 and has been perfected over the years, receiving a new patent in 1985. This dry process which cleans only with compressed air and an organic or mineral powder has established a long track record on historic structures in France. Powders used in this process are exclusively manufactured for Thomann-Hanry in France and are exported for use on foreign projects.

Facade Gommage has been the subject of several awards. Most notable are the "Prestige de L'Europe" and "Laurier d'Or" awards, given in 1990 for technical achievement in restoration. The company is also listed in the Guide of French Artisans d'Excellence for the cleaning of historic structures in France. Most recently, Thomann-Hanry was granted the symbol of "Qualite Ravalement" which is a recognized qualification for the contracting work on landmark buildings in France.

Currently, fifty percent of the company's cleaning projects are outside of France. It underlines their ability to work with international and local preservation commissions, labor issues, and diverse city/federal regulations. For instance, all Facade Gommage work on the Place Vendome (1979), Chateau de Versaille (1982), Cathedrale Senlis (1986), and Louvre Museum (1994 and 1995) required preliminary test panels which were later analyzed and approved by the Laboratoire Nationale des Monuments Historiques - Champs sur Marne. This government body approves restoration work on a case by case basis and does not disclose its test results. Similar operations happened with the National Park Service in the US and the Heritage Conservation Program of the Federal Government in Canada.

Perhaps the greatest scrutiny of Facade Gommage has been by representatives of UNESCO. Thomann-Hanry is proud to have cleaned three structures from UNESCO's World Heritage List as follows:

• Gaudi's Casa Mila - Barcelona, Spain
  Exterior cleaning in July, 1986
• Church Santa Clara Vahia - Coembra, Portugal
  Exterior and interior cleaning in July, 1992
• Jaronimos Cloisters - Lisbon, Portugal
  Exterior cleaning in November, 1992

Thomann-Hanry produced an award winning film entitled "Tu Es Pierre" in 1986 and has sponsored the publication of two books: Paris Facade and Demeures Parisiennes. In synergy with its main activity, the masonry cleaning, Thomann-Hanry has a division that exploits a limestone quarry in the Pont du Gare region of France.

II. Facade Gommage

The Facade Gommage process is based on projecting very fine powders with low pressure, compressed air to mechanically clean a surface. No water, chemicals, or detergents are used in conjunction with the powder/air mix. Thomann-Hanry adapts its particles with sizes ranging from 15 microns, 25 microns, 50 microns, or 90 microns. Because of their low mass, the particles have weak kinetic energy and remain in the air flow. As the air disperses outward on the surface, the particles follow and rub along the dirt layer. This buffing actions of the powder slowly diminishes soiling to a point where the masonry's surface is revealed.

All Facade Gommage projects are carried out by experienced cleaning technicians who follow the firm's training program in France. This process requires skilled craftsmen with acute visual control and steady hand coordination. To maintain even cleaning, the had-held nozzle that emits the powder is kept at a distance of approximately ten inches from the surface. The technician holds the nozzle at eye level and perpendicular to the surface, avoiding projection at angles whenever possible. Test samples are conducted on the masonry to determine the number of passes needed to slowly diminish the dirt layer. Using steady back and forth movements of the nozzle at a fixed distance from the surface, a trained technician is in control of the dirt removal, leaving behind an even appearance without surface damage. The vacuum system mounted behind the working deck serves to maintain a dust free environment for clear surface visibility.

The process has been used to clean dirt deposits from the interior or exterior surfaces in limestone, sandstone, granite, marble, brick, concrete, and exposed aggregate. Limitations apply in that Facade Gommage cannot properly clean wood, metal, glass, or deep-set stains. Also, painted, polished, or glazed surfaces must be evaluated on a case by case basis to see if an organic powder can be used for proper cleaning.

A. Particles

Since 1965, Thomann-Hanry has tested and applied several particle types for dry projections including sawdust, crushed nut shells, plastic powder, and alumina powder. However, these were found to have limited success and the firm has since focused its attention on two powder compositions: 1) organic powder, comprised mainly of crushed corn husks and used for delicate cleaning of some frescos, polished surfaces, and painted surfaces. 2) mineral powder, defined as aluminum silicate crystals and used on most masonry surfaces, including historic limestone which makes up 80% of the firm's Facade Gommage projects.

The particle, having the appearance of a thin, topaz powder, are neither toxic nor hazardous as per OSHA 29CFR 1910.1200. They meet OSHA requirements which specify that the respiratable fraction of silicates is less than .1 mg. per m3 of crystalline quartz and .05 mg. per m3 of cristobalite and tridymite.

In addition to composition, particle size is another important variable to control. Unlike sandblasting which uses grains of more than 400 microns, Thomann-Hanry gauges its powders at between 15 and 90 microns. Through test panels, a trained technician will determine the most efficient particle size that can clean without harm to the surface.


B. Compressed Air

The cleaning action of Facade Gommage begins with a controlled, humidity-free air flow in which the powder is mixed. At any given staging area for the air compressor, the equipment crew will take into consideration the hose line distance from the compressor to the cleaning technician's spray nozzle. By ensuring that the quantity of powder entering the airline does not vary and the cfm of the compressed air is controlled, Thomann-Hanry can work to maintain an even particle velocity leading from the nozzle.

Another important parameter with compressed air is the level of humidity which is created from the intake of humid air from the atmosphere and the action of compressing air within the unit, reaching temperatures of 200+ degrees. Through prefilter and heat exchanger units leading from the compressor, air can be cooled to the point where water is condensed and drained in separators before the flow is mixed with powder. In cases where the air is too saturated to properly separate all water, cleaning will be stopped until the weather condition changes.


C. Vacuum Cabin

The Thomann-Hanry Company has researched and developed a light-weight cabin in which the technician carries out the cleaning. This aluminum platform is fully enclosed except for a forward opening which faces the building facade. The opening is surrounded by an air-inflated canvas cushion to guard against surface damage while moving about the building. Four vacuum units are mounted at the rear of the cabin to immediately clear the workspace of dust and dirt. Once airborne particles are captured in the vacuums, they are moistened with a water spray and flushed in a slurry to a containment system at the ground level. this system not only aids the technician in maintaining precise visual control of the surface, but also avoids pollution of the environment.

The cabin measures 33 feet in length from end to end. In designated locations, sections of the platform may be removed in order to reduce the length to 26 ft., 19 1/2 ft., or 13 ft. Fully-manned and operational, it shall weigh a maximum of 3000 lbs. The two-man cabin crew consists of one member who cleans, while the other observes the results and controls cabin movement. There is also capacity for a third passenger to accomodate inspections by authorized representatives of the architect.


D. Access Equipment

Accessing the building facade can be done by 1) suspending the vacuum cabin, 2) mounting the vacuum cabin on a specialized boom truck, or 3) working from stationary foot scaffolds or mobile rolling scaffolds (enveloped with plastic sheeting).

The vacuum cabin is suspended by two Tirak 1020 motorized hoists using two 9 mm. braided wire ropes connected above to cantilevered beams as per architect's instructions. Two secondary 9 mm. wire ropes pass through a blocstop device which serves as a safety backup.

Designated areas will also be accessed using stationary and mobile scaffold systems. The perimeter of the scaffold will be covered in air-tight polyethylene sheeting supplied by Thomann-Hanry to facilitate a dust recovery system similar to that of the vacuum cabin. Portable vacuum units are positioned at the base of the scaffold to maintain a dust-free environment.


E. Ground Equipment

Equipment will be staged in areas so as to cause the least disturbance to building occupants while working at each elevation. The following equipment will be supplied by Thomann-Hanry and shall be utilized to perform the cleaning process.

- Powder diffuser. This specially manufactured unit mixes the powder with compressed air through electronically controlled trap plates which can be opened to designated widths. The cleaning technician is equipped with a remote control to operate the powder diffuser.

• Air compressor. Capable of 60 psi tip pressure.
• Electric generator. Diesel powered, 220 volts used to run vacuum units and hoists.

F. Hoses and Accessories

The Facade Gommage process uses industrial rubber hose leading from the powder diffuser to the hand-held cleaning nozzle with an 8 mm. aperture. The flow of air and powder can be stopped, started, and adjusted either by the cleaning technicians remote control or by the on-site equipment supervisor who operates from the powder diffuser instrument panel located at curbside. Other accessories include fresh air lines leading from an OSHA approved Clemco filter to the air-fed helmets worn by the technicians and a water hose attached from hose bibbs at designated locations at the building roof.

All lines leading from the suspended vacuum cabin are secured with wire ties to a separate cable in order to limit free movement and support weight. Other than the cleaning nozzle, no tools or materials are needed in the cabin.


G. Waste Disposal

All dust and waste particles are immediately sucked into a vacuum unit and trapped in a water spray filter. The slurry then runs through a discharge hose leading to containment bin at the ground level. This steel containment system is designed to drain the fresh water, while capturing the used powder for normal landfill disposal. The glass particles are inert and require no toxic waste permit.


H. Site Safety

• All ground equipment is protected with barricades and safety chain.
• Sidewalk canopies are erected beneath suspended cabin work.
• Cleaning technicians are equipped with OSHA approved, air-supplied helmets and upper body protective suits.
• Fall-arrest harnesses are properly secured to the body and attached by lanyard to polypro lifelines before stepping into the suspended cabin.
• Daily inspection of safety harnesses, supply lines, platform and related equipment are done by Thomann-Hanry supervisors prior to shift start.
• Housekeeping and clean up are performed at the end of every shift.