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The dark-brick one
Brown or grey-brown streaking running down the face and joints of dark, charcoal or brown brickwork — usually appearing right after the wall was cleaned, which is not a coincidence.
Looks like
Brown, grey-brown, tan streaking
Found on
Dark, charcoal and brown brick
Our verdict
Removable with the right chemistry
Quick answer
Brown or grey-brown streaking on dark bricks is manganese staining. Manganese dioxide is used to colour dark clay bricks, and acid cleaning dissolves it out of the brick face, allowing it to run down the wall and deposit on the brick and mortar below. It is most often created by the cleaning process itself. Removal requires a specific manganese treatment, generally an acidic reducing agent — hydrochloric acid alone makes it worse.
At a glance
Manganese dioxide is what gives dark bricks their colour. It is not a coating — it is part of the fired body. Hydrochloric acid dissolves it, and once mobile it runs down the elevation with the rinse water and redeposits, oxidising into a brown stain that shows up most obviously on pale mortar joints.
That is why so many manganese complaints arrive within days of a clean. The wall did not develop a stain. The clean created it.
Identify the brick before choosing chemistry. Where manganese is present, the wall is cleaned with a method that does not mobilise it, or with a treatment specifically formulated to keep manganese in solution so it rinses away instead of redepositing. Thorough saturation and a fast, complete rinse from the top down are essential.
A test patch on a small, low-visibility area will show you within minutes whether a brick is going to run. Skipping that step on dark brick is how whole elevations get ruined.
Manganese staining is treatable, unlike acid-set vanadium. It responds to an acidic reducing treatment that converts the manganese back to a soluble form so it can be rinsed clear. It usually takes more than one application, and the whole elevation is treated rather than the visible streaks so the finish stays even.
Several of these stains look similar and want completely opposite chemistry. Using acid on the wrong one turns a removable stain into a permanent one. Send a couple of clear photos in daylight — one close, one of the whole wall — and we will tell you what you are looking at.
FAQ
No. Unlike acid-converted vanadium, manganese staining generally responds well to the correct reducing treatment. It may take several applications on a heavily affected wall.
Manganese in dark clay brick is normal and expected. Brick manufacturers publish guidance on cleaning manganese-bearing brick precisely because the risk is known. Staining that appeared immediately after cleaning is a cleaning outcome, not a brick fault.
Yes, and it usually has to be, because pale joints are where the stain is most visible. The joints are treated as part of the elevation so the colour comes back uniform.
Identify it
White, powdery, fluffy
White, hard, crusty or glassy
Yellow, yellow-green, olive
Bleached, yellowed, patchy, exposed aggregate
Orange, red-brown, running streaks
Orange-brown, diffuse, blotchy
Black, green, grey-white patches
Black soot, brown scorching, tar film
Keep reading
Next step
Twenty years of masonry stain work across Sydney and the South Coast. If it can be removed, we will tell you how. If it cannot, we will tell you that too.