Cleaning sandstone blocks effectively involves addressing general dirt and specific issues like mould, often requiring different approaches. Keeping sandstone clean helps maintain its appearance and longevity.
The exact answer to cleaning sandstone blocks depends on the type of dirt or stain present. For general cleaning, gentle methods are preferred. However, for stubborn problems like mould, a stronger solution is recommended.
Tackling Mould and Algae on Sandstone
One of the most common issues affecting outdoor sandstone is the growth of mould and algae, especially in damp or shaded areas. According to the reference provided, the best way to clean sandstone affected by mould is to use a chlorine bleach solution.
Here's how to use a bleach solution based on the reference:
- Prepare the Mixture: Mix one cup of chlorine bleach with approximately 3.5 litres of water.
- Apply the Solution: Pour the mixture into a spray bottle.
- Spray Heavily: Concentrate the spray directly onto the areas of the sandstone blocks covered in mould or algae.
- Allow to Dwell: Leave the solution on the surface for 10 to 15 minutes.
- Repeat if Needed: For stubborn or heavy growth, repeat the spraying process.
- Scrub: After the dwell time(s), use a scrubbing brush to thoroughly scrub away the mould and the residual solution.
- Rinse: Rinse the area well with clean water.
Note: Always test the solution on a small, inconspicuous area first to ensure it doesn't cause any adverse effects or discolouration on your specific type of sandstone.
General Cleaning of Sandstone Blocks
For routine cleaning or removing general dirt, dust, and light grime, gentler methods are suitable.
- Dry Cleaning: Use a soft brush or broom to sweep away loose dirt, leaves, and debris. This prevents dirt from being ground into the stone when wet.
- Wet Cleaning:
- Rinse the blocks with plain water using a hose.
- For slightly more embedded dirt, use a mild detergent specifically designed for natural stone, or a pH-neutral soap. Mix it with water according to the product instructions.
- Apply the cleaning solution with a soft brush or sponge.
- Gently scrub the surface to lift the dirt.
- Rinse thoroughly with clean water to remove all soap residue.
Tools for Sandstone Cleaning
Selecting the right tools is crucial to avoid damaging the relatively soft surface of sandstone.
- Soft-bristle brushes (natural or synthetic)
- Brooms
- Spray bottles
- Hoses
- Buckets
- Avoid: Stiff wire brushes, high-pressure washers (unless specifically recommended by a professional for a particular stone type and used at a low pressure), and harsh acidic or alkaline cleaners which can etch or stain the stone.
Important Considerations
- Test First: Always test any cleaning product or method on a small, hidden area.
- Safety: When using chemicals like bleach, wear appropriate safety gear, including gloves and eye protection, and ensure adequate ventilation.
- Rinsing: Thorough rinsing is essential after cleaning to remove all traces of cleaning agents, which can otherwise attract dirt or cause residue build-up.
- Professional Advice: For significant staining, efflorescence, or if you are unsure about the best cleaning method, consult a professional stone cleaner.
By following these steps, including the recommended bleach method for mould from the reference, you can effectively clean and maintain your sandstone blocks.
