It is generally necessary to clean the dust from limestone prior to applying a sealant.
In the case of diamond cut limestone the dust created during the cutting process creates a slurry when mixed with the water used to keep the diamond cutting segments cool.
When dry this can appear like plaster on the stone face and must be removed to reveal the natural character of the limestone.
The process used to remove this involves a simple procedure using a high-pressure water cleaner.
However, it is very important to avoid directing the water directly at the face of the stone as this could remove softer material which, if left will harden when it dries or after the correct sealant is applied.
It is preferable to use a broader jet of water if possible and to tend to sweep the material from the face by applying pressure at an angle.
In most cases the stone has been freshly cut and is in it's softest state at that time due to the absorption of water during the reprocessing and its lack of exposure to the elements.
Allow the stone to dry before sealing as it must be able to absorb the sealant to a depth of about 20mm + - for long term effectiveness.
The time required to dry depends on the climatic conditions prevailing at the time.
Waterpel should be applied at the rate of about 1 litre per m2 to ensure the correct penetration when applied.
Note: As natural limestone is a porous material it can absorb water almost like a sponge and therefore demands greater amounts of sealant than is normally necessary.
The process to clean quarry-cut limestone is similar.
However, the method used in this case is more of a washing process as this dust is easier to remove.
Care must be taken as stone that is freshly cut directly from the quarry floor is softer and more prone to be damaged by high pressure than that which has been reprocessed through saws using diamond-tipped blades.
It essential that it is cleaned by low rather than high pressure.
Ideally, mains water pressure should be used by way of a normal garden hose fitted with a fitting which can create a broad/flat spray.
These inexpensive attachments can be purchased from hardware stores.
To wash the dust from quarry-cut stone, simply start at the highest point and work down sweeping/washing the dust before you.
Particular care should be taken to avoid dislodging loose material.
Quarry-cut limestone is generally more absorbent than diamond-cut stone and particular care should be taken to limit the application of sealant to 1 Litre per m2.