The object of cleaning sandstone and brick is to remove the offending or detrimental coating on the stone or brick with as little upset to the host stone or brick as possible.

Sandstone cleaned and finished correctly not only enhances the appearance of the stone but most importantly it improves the stone’s capability to shed water and ‘breathe’ as it should. The key word is ‘natural’; sandstone is a naturally formed porous stone varying, in colour, density and porosity.

Therefore, the benefits of cleaning and the method of cleaning have to be adapted to accommodate

  • The characteristics of the sandstone being cleaned, strong and dense or friable and excessively porous.
  • The colour of the stone, brown, red or blonde and its different natural composites (irons etc.)
  • The nature of the soiling natural (algae and moss) or man-made (carbon, paint, failing coloured sand coatings, cement)
  • Client expectations

Carbon or black stain removal

Sandstone is a natural substance. Whilst most soiling can be removed where excessive amounts of carbon have been absorbed by the stone over the years, cleaning may not change the black colouring/staining of the surface of the stone. Experience has shown that this is a trait especially noticeable with red sandstone.

When we are satisfied that to further clean a particular stone to remove carbon staining is going to be detrimental to the stone, it is a case of what you see is what you get! Gentle and minimally invasive cleaning is to the benefit of the stone and the client.

Salts

Sometimes you will notice that a white effervescence appears on your stone. This is especially noticeable in red sandstone due to the colour difference (white on red).

Although unsightly, this is good news in the sense that it means a stone that was previously unable to ‘breathe’ due to a coating causing it to retain excessive amounts of moisture, is now able to dispel the moisture. However, should you see this happening around a downpipe or a gutter, it generally indicates the stone is being saturated and the excessive moisture the stone is being subjected to, could point to a defect in your guttering or drainpipes. Other areas prone to this effervescence are foundations where excessive moisture has built up. The key is to find the cause and correct it.

Previously 'Sealed Sandstone'

A correctly maintained and ‘functioning’ sandstone building does not require the use of any type of chemical sealant. Unfortunately, there are those that ply the trade of ‘sealing sandstone’ – normally done in conjunction with a ‘cleaning’ from a high pressure washer. Effectively they are painting on or spraying a porous stone with a silicone based sealant thus sealing retained moisture in the stone and upsetting the natural balance of the stone’s capability to function correctly.

When it comes to a correct cleaning being done, and the surface is eventually smooth (in the case of smooth faced sandstone) and repelling water naturally, the stone looks beautiful on a dry day but ‘patchy’ on a wet day. This is because the silicone sealant has penetrated the stone deeper in certain areas than others.

Incorrectly Cleaned Sandstone and Brick.

A correctly maintained and ‘functioning’ sandstone building does not require the use of any type of chemical sealant. Unfortunately, there are those that ply the trade of ‘sealing sandstone’ – normally done in conjunction with a ‘cleaning’ from a high pressure washer. Effectively they are painting on or spraying a porous stone with a silicone based sealant thus sealing retained moisture in the stone and upsetting the natural balance of the stone’s capability to function correctly.

When it comes to a correct cleaning being done, and the surface is eventually smooth (in the case of smooth faced sandstone) and repelling water naturally, the stone looks beautiful on a dry day but ‘patchy’ on a wet day. This is because the silicone sealant has penetrated the stone deeper in certain areas than others. We always advise a test patch prior to the cleaning of your stone to determine if a sealant has been used or not; because in some cases the practical benefits of a cleaning may be outweighed by the disappointment of a ‘patchy when wet’ building.