A well-maintained memorial is a lasting tribute. Regular, careful cleaning not only keeps the stone looking its best — it also helps to preserve the inscription and prevent the kind of biological growth that, left unchecked, can cause long-term damage to the stone surface. This guide covers safe cleaning methods for the most common memorial stone types, and the products and techniques you should avoid.
If your memorial has significant biological growth, structural damage, or heavily worn lettering, we would recommend a professional restoration rather than attempting to clean it yourself. Our Restoration & Cleaning service covers all stone types and includes a full assessment before any work begins.
Before You Begin: General Principles
- Always use the gentlest method first — you can always do more, but you cannot undo damage
- Never use bleach, household cleaning products, or acidic cleaners on any memorial stone
- Never use a wire brush, abrasive pad, or anything that could scratch the surface
- Never use a high-pressure washer — the force can damage the stone surface and dislodge lettering
- Work on a dry day and avoid cleaning in direct sunlight, which can cause cleaning solutions to dry too quickly
- Always rinse thoroughly with clean water after cleaning
Cleaning Polished Granite
Polished granite is the most forgiving stone type to clean. Its dense, non-porous surface resists staining and biological growth, and it responds well to gentle cleaning.
What You Will Need
- A soft-bristled brush (a natural-bristle scrubbing brush or a soft toothbrush for detail work)
- A bucket of clean water
- A specialist stone cleaning solution (available from memorial masons and stone care suppliers) — or a small amount of washing-up liquid diluted in water for light soiling
- A soft cloth or sponge for rinsing
Method
- Rinse the stone with clean water to remove loose dirt and debris
- Apply the cleaning solution to the stone surface and work it in gently with the soft brush, paying particular attention to the inscription and any carved detail
- Allow the solution to dwell for a few minutes if there is significant soiling
- Rinse thoroughly with clean water, ensuring all cleaning solution is removed
- Allow to dry naturally
Cleaning Natural Stone (Limestone, Sandstone)
Natural stone is significantly more porous and more delicate than granite. It requires a gentler approach and more patience. Aggressive cleaning can remove the surface of the stone, damage carved detail, and accelerate weathering.
Biological Growth (Lichen, Algae, Moss)
Biological growth is the most common problem on natural stone memorials. The safest approach is to use a biological cleaning solution — a product specifically designed to kill lichen, algae, and moss without damaging the stone. These products work slowly, often over several weeks, but they are far safer than mechanical removal.
- Apply the biological cleaner to the affected areas according to the manufacturer’s instructions
- Allow it to work over several weeks — do not attempt to scrub the growth off immediately
- After the growth has died (it will turn from green or black to grey or white), it can be gently brushed away with a soft brush and rinsed with clean water
- A second application may be needed for heavy growth
General Soiling
For general dirt and soiling on natural stone, use clean water and a soft brush only. Do not use any cleaning products unless you are certain they are suitable for the specific stone type — many products that are safe for granite will damage limestone or sandstone.
Cleaning Slate
Slate is a relatively dense stone that responds well to gentle cleaning. It is more resistant to biological growth than limestone or sandstone, but it can be scratched if abrasive tools are used.
- Use clean water and a soft brush for general cleaning
- For biological growth, a biological cleaning solution can be used as described above
- Avoid any acidic products, which can etch the surface of the slate
- The natural colour of slate is usually fully recoverable with careful cleaning — do not be discouraged by a heavily weathered appearance
Caring for the Inscription
The inscription is the most important part of the memorial and deserves particular care. When cleaning around lettering:
- Use a soft toothbrush to clean inside carved letters — never a wire brush or anything abrasive
- If the lettering is filled with lead, paint, or gilding, take care not to dislodge or damage the fill
- If the lettering fill is worn or faded, this is a job for a professional — we can re-cut and re-fill inscriptions as part of our restoration service
How Often Should a Memorial Be Cleaned?
For polished granite, a light clean once or twice a year is usually sufficient to keep the stone looking its best. For natural stone, an annual application of biological cleaner will help to control growth and prevent long-term damage. If you notice significant soiling, structural damage, or heavily worn lettering at any point, please do not hesitate to contact us — early intervention is always better than waiting until the problem becomes severe.