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One of the best qualities of clay pavers is that they don’t stain easily and in most cases can be maintained perfectly with the simple use of a high-pressure hose. Should however any marks persist you can check out the Think Brick website (www.thinkbrick.com.au) to see how to keep your pavers maintained in prime condition by downloading their manual, or call their office to obtain a hard copy of the cleaning manual. Also if you are located in NSW you can call on Think Brick’s accredited cleaners to assist. Think Brick Australia, representing the clay brick and paver manufacturers of Australia and dedicated to promoting the beauty of brick, has compiled a list of common stains, how to identify them, and what to do to keep pavers looking their best.
The first step is to identify your stain and make sure you have the correct cleaning chemicals before you begin. You should always ask yourself, “are chemicals necessary?” If dry sweeping or washing with clean water and detergent isn’t working, it may be time to bring out the big guns. However, before automatically using an acid cleaner, it’s essential to identify what kind of stain you’re dealing with. See below for Think Brick’s list of common paver stains.
Secondly, Always follow the instructions on the label and take precautions. If you’re inexperienced, always test your selected chemical on a small, inconspicuous patch before tackling the full job. This will save you time and effort, particularly if the method used or the chemical selected proves ineffective.
There are few chemicals that are entirely safe and the same is true for paver cleaners. You can easily prevent potentially dangerous issues with a few elementary precautions:
· Wear protective clothing and eyewear to ensure you don’t inhale dangerous fumes or suffer acid burns.
· Safely store all chemicals after cleaning is complete.
· Dilute acids in the open with the breeze behind you.
· Keep children and animals away while working with chemicals.
· Always add acid to water, NOT water to acid.
White scum looks like a thin white film on the paver surface. Usually invisible when pavers are wet, it becomes obvious as the surface begins to dry. White scum often appears after you’ve attempted to remove mortar stains or sanded the joints using sand with high clay content.
White scum is particularly difficult to remove. Water, detergents, or spirits of salts (hydrochloric acid) often have no effect. However, scrubbing it with a proprietary cleaner will improve the overall appearance
Light-coloured clays often contain vanadium salt that discolours pavers. Neither permanent or harmful, in exposed areas the yellow, green, or reddish-brown stains will generally wash off in time. You can remove them faster by using readily available chemical treatments, such as:
(a) Sodium hypochlorite
Noskum is a general-purpose clay brick and paver cleaner that rapidly removes vanadium stains. Apply to dry pavers and wash off after the stain disappears.
The active ingredient in household bleach and pool chlorine, this is an inexpensive treatment for mild stains. Spray or brush it on without pre-wetting, allow it to stand until the stain disappears, then rinse off.
b) Oxalic acid
c) Noskum (proprietary cleaner)
This well-known chemical for vanadium stain removal must be followed by a neutralising wash or serious further staining can result. The correct procedure is to mix 20 to 40g oxalic acid per litre of hot water, apply without pre-wetting, and then neutralise by applying a solution of 15g washing soda per litre of water. Do not wash off.
Fresh mortar stains
Potassium hydroxide or sodium hydroxide (caustic soda)
Mix 150g of potassium or sodium hydroxide per litre of water and apply to the stain. Leave until the stain disappears, then wash off. If a white residue appears hose this off, too.
The simplest way to remove wet mortar stains is to lightly cover the pavement before the mortar sets hard with clean, slightly damp, washed sand.
Sweep the sand towards the edges of the pavement. If necessary repeat until the surface is almost clean. It’s important to remember that the sand MUST be free of clay. Follow with a further sweep using clay-free dry, washed sand. Any sticky wet mortar residues that escaped the wet sanding will be removed.
One or two days after the pavement has dried, some mortar residues may still be visible as a faint white film. Normally these will weather away. The appearance of efflorescence is almost certain, but don’t panic! Just complete the instructions below.
This harmless powdery deposit of white or yellow salts is often found on the surface of clay pavers after rain. Surrounding materials – such as soil or cement – are usually the cause. The best way to remove it is by dry brushing and hosing. However it’s sometimes necessary to follow up with a wash of weak acid or a proprietary cleaner.
Hardened mortar stains
Experiment on a small section of your pavement with decreasing proportions of water mixed with hydrochloric acid, starting with one part of acid to eight parts of water. Once you’ve determined the appropriate proportion of acid to water, or the proprietary cleaning solution needed:
1. Slightly wet the pavement with a fine spray of water
2. A final rinse of the pavement with a high-pressure water jet is often beneficial. Take care not to remove sand from the paver joints or damage pavers by overusing the jet.
3. Using a stiff brush, apply the acid over approximately one square metre. Vigorously scrub areas stained with mortar. If this doesn’t work, loosen thick mortar patches with a steel scraper. Work on the mortar stain until it is dissolved.
4. Give the area a good hose-down using a pressurised water spray unit. Repeat 1 to 3 until the whole pavement is clean.
Fungi, moulds, moss, and lichens
These are common, particularly in shady or damp areas. They sometimes appear as localised dark stains or patches of green, giving a dirty, unsightly appearance and slippery surface. Occasionally they might even add to your pavement’s appearance.
To remove, vigorously brush the affected area when it is dry or use high-pressure water. Even though the surface may appear completely clean, you should also sterilise the area with a poison or strong fungicide that needs three to four days to act. Blue crystals (copper sulphate), sodium hypochlorite (liquid chlorine or bleach) and formaldehyde are all options. Other brands are available from your local plant nursery. The surface should be brushed again when dry.
Be careful: Some fungicides may discolour pavement. Always test on a small area first and remember to pay attention to nearby garden plants or lawn, especially on the lower side of the paved area being treated.
Oil, bitumen, and tar
This will usually need two treatments with a commercial emulsifying agent. First, mix the emulsifier with kerosene to remove the stain. Then clean the kerosene off with the emulsifier mixed only with water.
If petroleum asphalt or bituminous emulsion is your problem, scrape off excess material and scrub the surface with scouring powder and water. Chilling the surface with ice or solid carbon dioxide causes brittleness for easier removal.
Any petrol or lubricating oil stains must be mopped up immediately with an absorbent material. Avoid wiping – it only spreads the stain and forces the oil into the pavement. Scrape hardened oil off and cover with a dry absorbent material such as diatomaceous earth, fine white clay, kaolin, or whiting. Repeat until there’s no further improvement. Clean up with detergent and water.
Food stains and tyre marks
Scrub with a full-strength commercial detergent and rinse well.
Wire brushes free from rust removes chewing gum, although it may take several attempts. Careful application of high-pressure water jets can also be successful. For smaller areas freeze each piece of chewing gum with a carbon dioxide aerosol or dry ice. You can then chip it off with a scraper or chisel.
If you’ve got a paving cleaning problem that hasn’t been addressed here, head to www.thinkbrick.com.au or call call Think Brick on 02 8962 9500