| 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 Maxiclene 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. |