Facade Gommage: Process Description

Façade gommage cleaning on the soft limestone of Vannes College in France	façade Gommage: This French term (prononced go-mahj) refers to the process of gently cleaning masonry by projecting very fine powders with low pressure compressed air. No chemicals, water, or detergent are used. The façade gommage process removes unsightly dirt and pollution deposits from interior and exterior surfaces of limestone, sandstone, granite, marble, brick, concrete aggregate stone, slate and stucco. It does not damage historic building fabric fabric in the short or long term and includes a dust containment system to ensure nuisance-free cleaning.
Removing years of dirt accumulation from the exposed aggregate façades at the International Building, San Francisco, California.	As shown above, the fine powder remains in the airflow as it diperses outward along the surface. In moving with the flow, these low mass particles slowly diminish the dirt layer with a rubbing action, unlike the direct, high-force impact of sand in traditional blast methods. Click here for examples. Thomann-Hanry selects its powders according to the type of masonry and nature of the soil deposit. The organic or mineral based particles emitted from the air nozzle range in size from 15 to 90 microns. Thomann-Hanry technicians follow an extensive training program and have the experience needed to permanently control dirt rmoval. They leave behind a uniform appearance without damage to stonework or mortar joints.
The Thormann-Hanry Company has researched and developed a light-weight vacuum cabin in which technicians carry out the cleaning process. The cabin is fully enclosed except for a forward opening which faces the building. Accessing the building façade can be achieved by suspending the vacuum cabin from outriggers, mounting the cabin on a specialized boom truck, or working from other access methods designed for hard to reach places.
AN ENVIRONMENTALLY SAFE CLEANING PROCESS ... *Thomann-Hanry's vaccum cabin.*	*Top: The vacuum cabin suspended from outriggers at Hotel DuPont in Wilmington* *Right: Delicate interior cleaning around stained glass panels at Senlis Cathedrale*
The cabin is equipped with vacuum units to immediately recover dust and dirt. This system not only clears the work space for precise visual control by the technician, but also keeps the surrounding area dust-free for pedestrians and building occupants. As airborn particles are captured in the vacuum they are moistened with a water spray and flushed through a hose to a ground level containment system. These non-toxic powders are safe for normal landfill disposal. The patented façade gommage process cleans effectively without water, chemicals or surface damage, and removes waste without contaminating the environment.	Bottom: The National Historic Monument Committee of France tested and approved façade gommage for the cleaning of Place de la Concorde in 1985