DOFF vs. Sandblasting: Which is Best for Your Facade?
The aesthetic of London is defined by its masonry, but after 150 years of coal fires, Victorian smog, and modern diesel particulates, most of that beauty is hidden under a thick black “carbon crust.” When homeowners decide to restore their property, the method of cleaning is the difference between a successful restoration and permanent masonry damage.
The Myth of the “Deep Clean”: The Danger of Abrasives
Historically, the go-to method for cleaning London brick was sandblasting or high-pressure grit blasting. While this results in a “clean” look, it is a destructive process.
A brick is not a uniform block of clay; it has a “fire-skin”—a dense, vitrified outer layer created during the firing process in the kiln. This skin is the brick’s only defense against the weather. Sandblasting grinds this skin away, leaving the soft, “biscuity” interior of the brick exposed to the elements. Once the fire-skin is gone, the brick will absorb ten times more water, leading to rapid damp and frost damage.
The DOFF Revolution: Heat as the Primary Solvent
We utilize the DOFF Superheated Steam system, the only method consistently mandated by Historic England for the restoration of listed buildings and national monuments.
- Thermal Shock vs. Kinetic Force: Traditional pressure washers use kinetic force (water pressure) to “blast” dirt away. The DOFF system uses thermal shock. By heating water to 150°C at the nozzle, it creates a superheated vapor that melts the molecular bond between the grime and the brick.
- Low Pressure, High Efficacy: Because the heat is doing the work, the pressure remains extremely low (equivalent to a garden hose). This ensures that even the most fragile, weathered bricks or delicate stone carvings remain completely intact.
- Biological Sterilization: London buildings often suffer from biological growth like algae, moss, and fungi. Standard washing leaves the microscopic spores behind. The 150°C steam of the DOFF system kills these spores instantly, meaning your walls stay clean for significantly longer.
When to Use the TORC System
For more stubborn stains—such as oil-based paints, bitumen, or heavy metallic staining—we utilize the TORC system. Unlike sandblasting, the TORC system creates a gentle, swirling vortex of low-pressure air, a tiny amount of water, and fine granules (calcium carbonate). It “peels” the dirt off in layers, allowing for surgical precision on delicate internal or external stone.
The Expert Verdict
Never allow a contractor to use a standard industrial pressure washer or sandblaster on a period London facade. Demand a “Low Pressure, High Temperature” solution to protect your home’s “fire-skin.”