Using Acid on Paving: Risks, Damage & Safer Cleaning Alternatives Explained
One of the commonest causes of complaints and problems on paving projects, is the liberal use of brick acid in one of its many forms. Builder’s Merchants sell various types of Brick & Patio Cleaners, designed to be used to clean mortar from brickwork, cement mixers, tools and just about everything else found on a building site. No need for site cleanliness – just use acid and everything will be clean!
The acid predominantly used is hydrochloric acid, which is a colourless, transparent liquid, used on site to neutralise alkaline agents e.g. mortar stains, and also rust and limescale. It is sold in various strengths, usually between 10% and 40% (100% hydrochloric acid can only be purchased under licence for use in manufacturing industries).
Ideally, it should only be used by trained and accredited staff, wearing full protective clothing, especially safety glasses and gloves, as it is highly irritant, creating instant holes in clothing and burns to skin. Even when purchased in a weak form, it should be further diluted to the minimum strength sufficient to do the job in hand, and never used undiluted straight from the plastic container.
As with all such products, the container should be disposed of in a manner that prevents it from being opened by the unwary (especially children in a domestic garden) and an accident occurs that could easily cost an eye.
Another acid in common use, also available from Builder’s Merchants, is Citric Acid which is used as a de-greasing agent for use on oil stains, especially on driveways and concrete floors. It may be used either manually or through a pressure washer, although full protective clothing is essential. It is considered a weak, colourless, organic acid, but should be treated with due care.
A third acid is called Acetic acid, which is a concentrated form of vinegar, and may be sold as such (Super Strength Vinegar) recommended by the manufacturers for cleaning patios and driveways.
Sometimes, Phosphoric acid is used in the maintenance and revitalisation of natural stone surfaces. It serves as a cleaning agent, employed to eliminate mineral deposits, hard water stains and other residues that may accumulate on materials such as marble, granite or limestone.
As with all chemicals, read and follow the instructions that appear on the containers. ALWAYS dispose of the containers in a safe and secure manner.
NEVER use acids on sandstones, granites, limestones or any other natural paving material, otherwise you run the risk of drawing iron deposits to the surface, which will permanently discolour the paving.
When you leave site, at the end of the project, make sure the owners are made aware of this fact in the future, should they decide to ‘clean’ the patio at any time.
