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Types of Stains on Bricks and Brickwork – With Images

Example of Efflorescence, a white powdery deposit that forms from moisture in bricks drawing minerals and salts to the surface as it dries. Image 1.

Staining may occur on brick surfaces due to minerals and salts leaching from the bricks, or a reaction or contaminate left on the brick surface.

Here, we showcase various types of stains and discolouration in brickwork and describe treatment techniques using acid wash pressure cleaning.

Efflorescence

  • Cause: Efflorescence is caused by soluble salts and moisture in the bricks or concrete. These salts deposit on the surface as the excess water evaporates.
    It commonly occurs in brickwork that hasn’t dried completely or when brick pallets are left exposed in water puddles.
  • Appearance: Powdery, sometimes fluffy, white or greyish deposits on the surface of bricks.
  • Treatment: Most efflorescence will naturally disappear over time, but removal can be accelerated by brushing with a stiff dry brush. For persistent cases, an acid wash may be used to dissolve and remove the salt deposits.
  • Example of Efflorescence, a white powdery deposit that forms from moisture in bricks drawing minerals and salts to the surface as it dries. Image 1.
  • Example of Efflorescence, a white powdery deposit that forms from moisture in bricks drawing minerals and salts to the surface as it dries. Image 2.
  • Example of Efflorescence, a white powdery deposit that forms from moisture in bricks drawing minerals and salts to the surface as it dries. Image 3.

Efflorescence – Moisture in Bricks from Pallet exposure to water.

Images showing discolouration in a row of bricks (laid from the same section of the brick pallet), resulting from moisture.

  • Dark brick wall showing a row of bricks that have uniform discolouration, resulting from moisture in these bricks as the pallet was left exposed sitting in a water puddle.
  • Dark brick wall showing a row of bricks that have uniform discolouration, resulting from moisture in these bricks as the pallet was left exposed sitting in a water puddle. Image 2.

These bricks were likely from the bottom of the pallet and left exposed sitting in a water puddle. As these bricks dry they show more efflorescence than other bricks from the same build.

Calcium Stains

  • Cause: These stains result from the chemical reactions between Portland cement and bricklaying sand containing clay. They develop in stages:
    • Stage 1: White streaking deposits resembling cracks or drips.
    • Stage 2: Beginning white cracks with buildup.
    • Stage 3: Larger white masses that can flake off with a finger.
  • Appearance: Calcium stains manifest as a milky film that is hard and white when dry but invisible when wet.
  • Treatment: Specialised brick cleaning acids can effectively remove calcium stains by dissolving the deposits.
  • White streaking Calcium deposits on a brick wall, that look like cracks or dripping. Image 1.
  • White streaking Calcium deposits on a brick wall, that look like cracks or dripping. Image 2.
  • Large mass of a white Calcium stains - Calcium deposits on a brickwork.

Iron Oxide (Rust) Stains

  • Cause: These stains result from a chemical reaction of hydrochloric acid and iron-rich clays in the bricks.
  • Appearance: Commonly confused with Acid Burns, Iron oxide stains appear as yellow, orange, or brown rust-like discolourations on the brick surface.
  • Treatment: Iron stains normally disperse after a couple of weeks. For persistent cases, phosphoric acid or oxalic acid is effective in breaking down and removing these rust stains, restoring the brick’s original appearance.
  • Patch of brown iron oxide discolouration on brickwork, resulting from a chemical reaction of iron in the brick clay and acid treatment.
  • Brown - orange iron oxide discolouration on bricks resulting from a chemical reaction of iron in the brick clay and acid treatment.
  • Slight brown - yellow iron oxide discolouration on corners of some bricks, resulting from a chemical reaction of iron in the brick clay and acid treatment.

Acid Burns

  • Cause: Sometimes a Brick Cleaner can miss spots treated with acids and accidentally leave chemicals on the bricks.
  • Appearance: As the acid dries it leaves a powder over the brick surface, and in severe cases leaves a greenish tinge to the bricks.
  • Treatment: Fresh unreacted acid wash may be used to remove the deposits, followed by correct water wash down.
  • Darkened patches on brickwork from acid burns. eg. acid left on for too long.
  • Minor green tinged acid burns on left hand edge of bricks from acid left on for too long, by not getting washed off.

Images of dried acid on brickwork forming a powdery substance.

  • Dark brick wall covered in a light powdery residue resulting from dried acid.
  • Dark brick wall after washing to remove the dried acid.

Weathering Effect on Bricks

Over time, weather can cause moss, dirt, and other stains to develop on brick surfaces.

  • Dark black brown weathering stains on bricks from dirt, moss, algae and other stains - image 4
  • Dark black brown weathering stains on bricks from dirt, moss, algae and other stains - image 3
  • Dark black brown green weathering stains on bricks from dirt, moss, algae and other stains - image 2
  • Dark black brown weathering stains on bricks from dirt, moss, algae and other stains - image 1

Vanadium Stains

  • Cause: Vanadium stains are caused by light-coloured clays that contain vanadium salts. These salts deposit on the surface structure as the excess water evaporates from the brickwork.
  • Appearance: These stains can appear as yellow, green, or reddish-brown discolourations on the brick surface.
  • Treatment: Effective removal using sodium hypochlorite, oxalic acid, potassium hydroxide, or proprietary cleaners. Recommended to test on a small area first to determine the most suitable chemical treatment.

Manganese Stains

  • Cause: These stains occur on bricks coloured with manganese during manufacturing (various shades of brown or black) and are generally caused by excessive water penetration drawing salts to the surface structure as the excess water evaporates.
  • Appearance: Manganese stains appear as dark blue-brown discolourations along the edges of the brick or across the face of the brick in severe cases.
  • Treatment: Phosphoric acid or acetic acid can be used to treat manganese stains, although preventing their recurrence is key, which may involve construction adjustments to minimise water penetration.

Data referenced from Midland Bricks – Brick Cleaning & Stain Removal