Limestone gives many of Britain finest buildings their warm, pale colour, but it is soft and chemically sensitive. The wrong cleaner can etch it permanently. This guide explains how to clean limestone safely.
Key takeaways
- Limestone is soft and reacts with acids, so acidic cleaners can etch and dull the surface.
- It forms a black crust in polluted areas, much like other heritage stone.
- Pressure washing soaks the soft stone and can erode the surface and detail.
- Laser cleaning removes soiling and crust without acids, water or abrasion.
Why limestone needs special care
Limestone needs special care because it is a soft, calcium-based stone that reacts with acids, so acidic cleaners can dissolve and etch the surface, leaving it dull and pitted. Its chemistry is its weakness.
It is the stone of cathedrals, Cotswold villages and Georgian terraces, and its soft, warm surface is exactly what makes it both beautiful and easy to damage.
The problems with common methods
Common methods cause problems on limestone: acidic chemicals etch it, alkaline ones can leave salts, and pressure washing soaks the soft stone and erodes the surface and carved detail. Each carries a specific risk on this stone.
The black crust that builds up in polluted areas is hard and bonded, so removing it without taking the soft stone with it is the central challenge, as it is with other heritage masonry. See removing black crust from stone.
How laser cleaning suits limestone
Laser cleaning suits limestone because it removes soiling and crust with light, with no acids, no water and no abrasion, so the soft, reactive surface is not etched, soaked or worn. It avoids every one of limestone main risks.
Its selectivity, removing the dark crust while sparing the pale stone, makes it especially effective here, and it is recognised within BS 8221-1:2012. See our heritage stone cleaning service.
Need this done by professionals?
LaserStrip provides mobile laser cleaning across the UK. Heritage approved, chemical free, fully insured. Tell us about your project for a fast quote.
Getting a sympathetic finish
A sympathetic finish on limestone reduces the soiling evenly while keeping the natural, warm colour of the stone, rather than bleaching it to a hard, uniform white. The character of the stone is the point.
LaserStrip cleans limestone and other heritage stone across the UK. Send photos for a quote through our contact page, or read BS 8221 explained.
