|Acid Burn (iron oxide stain)||Yellow, orange to brown rust-like stain.||Frequently a result from the incorrect use of hydrochloric acid when cleaning, leading to iron oxide staining.||Phosphoric acid or Oxalic acid applied as per instructions in the Brick Cleaning Manual|
|Calcium Stains||Appear as almost a milky film on the brickwork. These hard white deposits are invisible when wet but insoluble in water.||Most commonly these stains arise from products of the setting reactions of portland cement and bricklaying sand containing clay.||The application of Noskum or an equivalent product at full strength will usually remove these stains.|
|Vanadium Stains||Light-coloured clays often contain vanadium salt that are generally colourless, but under certain conditions may appear as a yellow, green or reddish-brown discolouration of the brick.||Often generated by the use of too strong a concentration of hydrochloric acid during the initial cleaning process, or from excessive water penetration.||Sodium hypochlorite, Oxalic acid, Potassium hydroxide or sodium hydroxide (caustic soda) or Proprietary cleaners.|
It is best to test the efficiency of these chemicals on a test area to determine the most suitable treatment to use.
|Efflorescence||Efflorescence is not a stain, it is a powdery and sometimes 'fluffy' deposit that forms on the surfaces of porous building materials such as masonry units, mortar and concrete.||The formation of efflorescence requires three conditions:|
- The presence of soluble salts.
- Excessive amounts of water entering the masonry.
- The evaporation of water as the masonry dries out, depositing salts on the surface.
|Most efflorescence will naturally disappear over time, however its removal can be accelerated by brushing with a stiff dry brush. The use of a dust pan or vacuum cleaner to collect the salts after brushing is recommended as this will prevent salts from re-entering the brickwork or any porous paving materials below.|
|Graffiti & Paint||Fresh aerosol paint, dried paint, oil-based paints or enamels.|| ||Refer to manual|
|Iron & welding splatter||Rust stains||Where unprotected steel is built into masonry, unsightly rust stains may result on both bricks and joints. Similar stains will occur if welding is carried on too close to masonry.||Phosphoric acid, Oxalic acid or Proprietary cleaners|
|Oil, bitumen & tar stains|| ||These stains generally arise from the actions of other trades or due to a lack of care in protecting materials in the structure.||Refer to manual|
|Organic Growths|| ||These are common where masonry is in contact with damp soil, such as flower boxes, retaining walls and in sunless spots.||As much growth as possible should be removed by vigorous brushing with a bristle brush. For heavy growth, scraping and wire brushing may be necessary.|
After this dry cleaning, apply a proprietary weed killer or liquid chlorine.
|Smoke stains|| ||These stains vary from minor conditions around domestic open fireplaces to major problems of cleaning of face masonry in fire-damaged buildings.||Minor stains can be removed readily with sugar soap that is a highly alkaline mixture.|
For smoke-damaged buildings an initial treatment with sugar soap will remove some of the deposits. This can be followed by an application of sodium hypochlorite.
|Soil & grime|| ||These stains arise from long-term airborne deposition. Grime is worst in industrial areas with heavy pollution problems. Special cases can arise, for example from bird fouling or proximity to railway lines.||Scrubbing with a fibre or soft bronze bristle brush and a liquid detergent is usually effective.|
Large jobs are usually carried out by specialist cleaners using high-pressure water and dry or wet sandblasting
|Timber stains||The stains are usually brown or grey and are present on both bricks and mortar.||Timber stains usually arise from water spreading tannin or resin stains on the wall, particularly from hardwoods.||Normally timber stains will be removed by scrubbing with a solution of 20-40 grams oxalic acid per litre of hot water.|
Neutralise the wall after this treatment.
|Manganese Stains||A dark-blue brown discolouration may occur on bricks that have been coloured grey or brown by the addition of manganese during manufacture.||The stain occurs most characteristically along the edges of the brick and is generally caused by excessive water penetration. In severe cases it may show as a stain across the face of the brick.||The problem with manganese staining is not so much the removal of the stain, as preventing its return in a short period by certain methods during construction. If it does occur, Phosphoric acid or Acetic acid can be used.|