For this reason, it is important to ensure that the correct cleaning methods are utilised for the best results and to help reduce any associated problems with cleaning. Brick Manual 3 outlines the techniques that should be employed.
Acid cleaning using hydrochloric acid (HCl) should normally only be used to remove mortar stains. Therefore, only pavers that have been wet-bedded may require acid cleaning. Generally, hydrochloric acid should not be used to treat any other stains or at any other time during the life of your clay product. If used incorrectly, it can cause unsightly staining that is more difficult to remove. The correct technique for cleaning mortar stains of brickwork with hydrochloric acid is given in Brick Manual 3.
The practice of cleaning mortar residue ‘as you go’ during laying should normally eliminate the need for acid cleaning. Wet-bedded Riviera pavers should normally be cleaned using this technique. If acid cleaning is used, particular care should be taken to follow the correct cleaning procedure.
Any vanadium stains should be treated prior to acid cleaning. Vanadium stains are a yellow-green harmless discolouration on the face of a clay product, which can occur especially in light coloured clay products. Acid cleaning prior to treating vanadium stains can result in the stain becoming more unsightly and more difficult to remove.
‘Acid burn’ is caused by the use of an incorrect acid cleaning procedure. The acid reacts with iron oxides naturally present in pavers or mortar to cause the stains.
- Always use adequate safety precautions!
- Reduce the need for acid cleaning by cleaning ‘as you go’ during laying.
- Ensure sufficient pre-wetting of the pavers prior to applying hydrochloric acid.
- Apply an acid solution of the correct strength. Acid solutions that are too strong are a problem.
- Ensure that the pavers are sufficiently rinsed after cleaning. Light coloured pavers should be rinsed with a neutralising solution.