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5 Common Natural Stone Stains and How to Remove Them

Natural stone is a popular choice for outdoor patios, pathways, and steps due to its durability and timeless beauty. However, even with its tough durability, natural stone is susceptible to stains. Stains can be unsightly and detract from the beauty of your stone surfaces. Let’s explore the 5 most common stains found on natural stone and how to effectively remove them!

Algae Stains

Algae stains are common with natural stone, especially in areas with high levels of moisture and low levels of sunlight. They give your stone a green or brownish colour and can be very slippery. If left untreated through warm summer months, the algae can turn black, causing further unpleasant stains.

To remove algae stains, follow these steps:

  1. Clear leaves and general debris site being treated.
  2. Using RPB Algae Remover and Patio Reviver, dilute the contents of the bottle in 4 litres of water and apply with a low-pressure spray, watering can or brush.
  3. Saturate the surface with the Algae Remover, and then leave to dry.

Blackspot & Lichen Stains

Blackspot and lichen are another common stain that is found in damp shaded areas. They appear as black or green patches and can be quite difficult to get rid because they are a living organism and can reappear quickly if not treated correctly.

Here’s how to effectively remove them:

  1. Sweep and clean surface being treated from debris.
  2. Using RPB Patio Cleaner, apply the product undiluted to the surface using a stiff brush to ensure good contact with the surface.
  3. Ensure the surface is saturated with the cleaner and leave for between 10 and 60 minutes, or overnight if infestation is bad.
  1. Do not allow surface to dry during treatment. Ensure that the product does not evaporate by covering with thin plastic. 
  2. The black spot and lichen will now be dead but still adhered to the treated surface. To remove, rinse off with water using a stiff bristle brush or a power washer to dislodge the dead black spot and lichen.

Rust Stains

Rust stains can occur when natural stone oxidates, from metal objects or furniture, harsh chemicals like brick acid being used, and even spilt fertiliser. It leaves orange-brown marks which look terrible and can have you thinking your natural stone is now ruined.

Here is how we remove rust stains:

  1. Apply RPB Rust Remover with a paint brush or roller to the affected area. If a large area needs to be covered, then dilute the product 1:10 with water.
  2. Leave to sit for 5-15 minutes.
  3. If the stain is stubborn, repeat again.
  4. Thoroughly rinse surface with water

The stain rust marks may return after being treated. Depending on the iron concentration within the stone, repeat applications may be required until the stone stabilises.

Cement Stains

During construction or renovation projects, cement stains may occur, which unless removed carefully, can cause damage to your natural stone. Avoid brick acid, as this will cause rust stains to appear in your stone.

Follow these steps using RPB ConClear to remove cement stains:

  1. Shake the ConClear bottle for 30 seconds before use.
  2. Use neat or diluted (1 vol Conclear to 2 vols water).
  3. Pre-wet the affected area with water.
  4. Apply the ConClear evenly over the contaminated area, using a low-pressure sprayer.
  5. Re-apply after 10 minutes and leave for a minimum contact time of 45mins.
  6. It is important to keep the treated surface moist during the treatment stage as a dry surface means the cleaning reaction has stopped. Cover to protect from evaporation if necessary. However, if the surface does dry, then re-apply the ConClear.
  7. Rinse off thoroughly with water using a pressure washer.

If you have rust stains on limestone, then use sparingly only on affected areas, leave on for only as long as necessary and do not let it dry.

Grease and Oil Stains

Grease and oil stains can be frustrating to remove from natural stone surfaces, as they can penetrate deep into the stone’s pores.

To tackle these stains effectively, use RPB Heavy Duty Cleaner:

  1. Use RPB Heavy Duty Cleaner either neat or dilute as necessary. (Maximum dilution ratio is 1 part product : 10 parts water).
  2. Apply using a brush or spray and allow to penetrate the oil or grease.
  3. Agitate with a stiff brush if using on heavily soiled area.
  4. Rinse clean with clean pressurised hot water.
  5. If large area, vacuum up dirty water and loosened residue with a wet and dry vacuum. If in a confined area, use a low-pressure hose and scrubbing brush.

Stains on natural stone surfaces are common and with the right knowledge and cleaning products are very manageable.