Cleaning
It is very difficult to remove mortars and contamination from surfaces of cast stone. It is for this reason that every effort should be made to avoid contamination.
The removal of mortar from the surface can be carried out by physically removing as much of the mortar as possible using a semi-stiff, non-metallic brush, followed by mild acid washing.
Once all contamination has been removed and stonework acid washed, a final wash down using clean water should be performed to avoid further aggressive action by the acid.
Cleaners
Contamination due to cleaning of higher courses of brickwork or other materials should be avoided. Advice should be sought before carrying out this type of work.
Oil and grease can be removed by using a chemical degreaser. As with all treatments, this should be tested on a small, non-visible area first to investigate any colour shade variation that may be caused.
If unsure, please contact our technical department prior to performing any cleaning.
Repair Work
In many cases it is possible to repair chips etc. The recommended techniques vary, and advice should always be sought. It should be noted that repair work is normally carried out with material mixtures similar to those used in the original product and will take time to weather to the colour of the item being repaired.
Note: We recommend the use of specialist companies for cleaning and repair work. Please ask for details. Should you feel confident enough to perform the repair yourself, the below guidelines should be followed.
Repair mix can be requested from our sales office. Repair mix supplied should be mixed with WHITE CEMENT at the below ratio.
Ratio 1:5 (White Cement : Pointing Mix)
Mix as for pointing (see separate guide). Use a small amount of PVA with the water. A small amount of PVA and water may also be applied to the damaged area. Avoid contact with the surrounding stone, as staining may occur. Bonding agent should be diluted in accordance with the manufacturer's instructions.
Bloom (efflorescence) may occur if the repair mix used is too wet. Treat this as standard efflorescence. A light rub with dry sandpaper will help.
To perform small repairs, ensure the damaged area is clean and contains no contaminants. Use proprietary cleaning materials if required. If acids are used, follow manufacturer's instructions and wear all recommended safety equipment. Take care to thoroughly wash all acid from the stone prior to commencing repair.
Using a trowel or similar, press the repair mixture into the damaged area and leave the mix slightly proud of the stone face.
Once completely dry, use a fine grade carborundum block with copious amounts of water to rub down the repair until level with the stonework face. Avoid rubbing down any undamaged areas of stone.
Once the damaged area has been prepared, repaired and rubbed down, a good wash off with water will help the appearance of the repair.
Please note that the area treated may take time to weather in with the existing stonework. If the repair is carried out on a ready weathered unit, it may be necessary to clean the whole unit to achieve a better finish. Use a proprietary cleaner and follow recommended guidelines.
Finally, to ensure the water tightness of the repair, it is prudent to seal with a silicon material. Care must be taken to select the correct silicon, as some products can affect the appearance of the stonework. Suitability tests are recommended.
Note: This is issued as guidance only, and Serene Stone Limited will accept no responsibility for its implementation.
