Tips for Cleaning Bluestone Flagging

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Different issues need different cleaners:

• Black/green stains → algae, mold, or mildew
• White/gray haze → efflorescence (mineral buildup)
• Rust/orange spots → metal or fertilizer staining
• General dullness → dirt, oxidation, and weathering

If you’re not sure, assume it’s a mix of grime and organic growth and start with a mild approach.

1. Use an Alkaline Stone Cleaner (not acid-based).
   
   • Products like Prosoco Sure Klean 600, Wet & Forget Outdoor, or StoneTech KlenzAll are good options.
   • Mix and apply per the instructions — typically dilute in water, apply with a pump sprayer or stiff brush.

1. Scrub with a stiff bristle brush (not wire).
   
   • Work the cleaner into the stone and joints.
   • Let it dwell 10–15 minutes but don’t let it dry out.

1. Rinse thoroughly.
   
   • Use a garden hose or low-pressure washer — high pressure can erode the stone surface.

1. For tough stains, repeat with a specialty cleaner:
   
   • Efflorescence: Prosoco “Light Duty Concrete Cleaner” or “Efflorescence Remover”
   • Rust: Iron Out or a dedicated rust remover safe for natural stone
   • Organic stains (leaves, mildew): Hydrogen peroxide (12%) diluted 1:1 with water

Once clean and dry (let it dry for at least 48 hours):

• Enhance the color:
  Apply a stone enhancer/sealer (e.g., StoneTech Enhancer Pro, Miracle Sealants 511 Seal & Enhance). This darkens the stone slightly and revives that “wet look” richness.
• Or keep natural tone:
  Use a penetrating sealer like Dry-Treat Stain-Proof or Aqua Mix Sealer’s Choice Gold — protects against stains and moss without changing color.

Apply with a paint roller or sprayer, let it absorb, then wipe off excess.

• Test any cleaner or sealer on a small hidden area first.
• Avoid acidic cleaners (vinegar, muriatic acid) — they etch and dull bluestone.
• Regularly sweep and rinse to prevent organic buildup.
• Reapply sealer every 2–3 years depending on weather exposure.