Porous stone surfaces, such as limestone, sandstone, and travertine, are prone to biological staining caused by algae, mold, and lichen. These stains not only mar the appearance but can also degrade the stone over time. Here are the most effective methods to prevent and address biological staining:

1. Seal the Stone Regularly

Apply a high-quality penetrating sealer designed for porous stone. Sealers create a protective barrier that repels moisture, a key factor in biological growth. Reapply every 1–3 years, depending on exposure and climate.

2. Routine Cleaning

Use a pH-neutral stone cleaner to remove dirt and organic matter before stains set in. Avoid harsh chemicals like bleach, which can damage the stone and encourage further staining.

3. Control Moisture

Ensure proper drainage around stone surfaces to prevent water pooling. Indoors, use dehumidifiers in damp areas to reduce humidity levels that promote mold and algae growth.

4. Natural Remedies

For light stains, a mixture of water and white vinegar (50:50) can be effective. Apply sparingly and rinse thoroughly to avoid etching. Baking soda paste is another gentle option for spot treatment.

5. Professional Restoration

For deep-set stains, consult a stone restoration specialist. Techniques like poulticing or steam cleaning can safely remove biological growth without harming the stone.

By combining these preventive measures with consistent maintenance, you can keep porous stone surfaces pristine and free from unsightly biological stains.