Paving should always be laid on a solid bed of sand and not by use of the “Dot and Dab” method as this will weaken the stone’s integral strength and can result in spots of discolouration on the surface.
Strongly coloured, soft sand (ie. Orange) can occasionally bleed through newly laid stone leaving a residue, changing the natural colour of the stone. Preferably, use of a more golden coloured or sharp sand will reduce the possibility. Equally, white cement eliminates this problem. Coating the back of the slabs prior to laying with Sealer or PVA will help in this matter.
Efflorescence or light powdering due to Building Salts are generally caused by water in the concrete or from the ground below the slabs being drawn up through the stone depositing on the surface. These will normally diminish and cease after a few weeks. More stubborn marks should be cleaned off with the use of a suitable cleaning agent or household vinegar.
Mortar stains should be cleaned off from the face of the slabs as work is in progress with clean water and not be left until the completion of the work as the staining will be set in and be more difficult to remove.
The use of harsh cleaners, such as Brick Acid, should be avoided ‘at all costs’ as this is likely to cause significant discolouration of the natural stone slabs.