Brick Stain Removal

This is only a summary guide and is not exhaustive. It does not describe how to clean stains, the removal procedures, proportions of cleaning products and safety requirements.

Please read The Brick Cleaning Manual for full information.

Stain Description Cause Removal
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.