clay and iron oxides
• colour depends on the proportions of minerals in its makeup
material which allows a wide range of acceptable cleaning techniques, including water and chemical-based processes
• can offer a lifetime of low maintenance but essential to identify staining causes for remedial action
• water-based release of white salt deposits, known as efflorescence, is a transitory effect and may weather away naturally
• excessive wetting can easily force salt deposits back into it only to re-emerge again later
• lime staining, which emanates from mortar joints, stone or concrete components when they become saturated are typically seen on the line of a mortar joint and running down in streaks
• the build-up of dirt, grime and soot take place over long periods of time and are generally the result of airborne deposition
• for both lime staining and efflorescence, façade gommage offers a gentle alternative and improved results on most bricks
• predominantly white, pink or grey
• coarse-grained, crystalline igneous rock
• hard, tough and massive (lacks any internal structures)
• widely used in the construction of buildings and memorials throughout history
• the introduction of steam-powered cutting and dressing tools in the 19th century improved the results of hand carving
• followed by modern carving techniques such as computer-controlled rotary bits and sandblasting
• low porosity and permeability meaning water-based cleaning techniques are suitable
• scaffold-free façade gommage technique offers an easier solution than removing cladding to allow scaffold to be tied in
Unlike some traditional façade cleaning methods, façade gommage® gently cleans without abrasion, and is highly effective across a wide range of materials and surfaces. 1 Poultry, London Restoring Excellence We remove dirt, not surface detail Limestone • formed at the bottom of shallow lakes and compacted over the ages • primarily consisted of calcium carbonate, it’s hard and durable • used widely from the Great Pyramid at Giza in Egypt onwards • featured in façades, cornices, pillars, floors and staircases • reactive to acid solutions so acid-based cleaning chemicals are not advised, as they can etch the surface • non-aggressive, façade gommage suits perfectly Sandstone Terracotta So whatever material you’re looking to clean and restore, you’re in safe hands with Thomann-Hanry To find out more and get a free quote, contact us via 020 8453 1494 or info@thomann-hanry.co.uk Restoring Excellence • features warm, distinctive honey tones • used widely since Roman times across Southern England –nowhere more so than the iconic World Heritage city of Bath itself • made up of granular fragments of calcium carbonate, classified as an oolitic limestone • most quarries are now converted to other purposes • easy to work, it’s a “free stone” – can be squared up or sawn in any direction, unlike layered rocks such as slate • highly susceptible to dirt and decay • is highly porous, and water-based cleaning techniques should be avoided as well as chemical cleaners, which can accelerate decay • features a distinctive pink or pale-yellow colour • is a Jurassic oolitic limestone, used in construction since the 16th century • named after the Rutland village of Ketton • widely used some 60 miles away in Cambridge on many colleges • a “free stone” – can be sawn or squared up in any direction • porous material, militating against water and chemical-based cleaning processes • King’s College Cambridge chosen façade gommage technique to gently rub off and lift away years of accumulated dirt and grime • composed of fine and coarse aggregate bonded with fluid cement which cures (or hardens) over time • used more than any other artificial material in the world • offers durability and long service life coupled with excellent fire resistance and the potential for creative finishes • ton for ton, its worldwide use is twice as much as steel, wood, plastics and aluminium combined • durable and suitable to many water and chemical-based cleaning techniques • material of choice for many of London’s largest monolithic buildings and issues of access and scaffolding frequently occur • façade gommage scaffold-free system is a practical solution • clastic sedimentary rock • made up of sand-sized mineral particles, rock fragments (clasts) or organic material • most is composed of quartz or feldspar, silicates which are highly resistant to weathering processes at the Earth’s surface • varies greatly in colour, depending on the impurities within • an ideal building material, easy to carve • generally good resistance to weathering, used as a building material since prehistoric times • its softness as a substrate can also make water and chemical-based cleaning techniques problematic • consisting of quartz, mica, feldspar,
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• tight-grained, Carboniferous sandstone, sourced from quarries in Yorkshire since medieval times • mainly cut and pressed from quarries around Holmfirth, West Yorkshire
featured in most London paving
hard-wearing and durable, even in harsh weather conditions
• clay-based substrate translated as “baked earth” • features in many Victorian buildings in Birmingham • the inter-war ascent of concrete in Modernist architecture in the 1930s drew a line under terracotta as a building material • soils badly and thick encrustations of sooty deposits can build up all too easily, potentially concealing structural defects • friable, façade gommage is ideally suited, as a gentler solution than water or chemical cleaning techniques • prepared, cast and cured off-site • can often prove to be more economical and practical than cast-in-place concrete • the ingress of water between joints can give rise to structural issues • regular inspection and cleaning is essential to avoid problems escalating, potentially hidden by layers of accumulated dirt and grime • a
• susceptible to damage from water-based cleaning techniques but more resilient than many materials
