Gutter Care · 4 min read

What Causes Black Streaks on Gutters (And How to Get Rid of Them)

May 2026 · By Chad — New Home Glow

Those streaks aren't dirt. You can pressure wash them all day and they won't budge. Here's what they actually are and the only method that removes them — without damaging your gutters.

What The Streaks Actually Are

The technical name is tiger striping or oxidation staining. It's a chemical reaction, not surface dirt.

Here's what's happening: rainwater rolls off your roof, picks up acidic residue from asphalt shingles (a mix of dirt, hydrocarbons, and weathered tar), and runs across the painted aluminum face of your gutter. Over years, that acidic runoff oxidizes the painted finish. The result is the dark vertical streaks you can't scrub off.

Pressure washing won't fix it because the staining is bonded to the paint at a molecular level. You need to dissolve it chemically, not blast it physically.

What Doesn't Work

What Actually Works: Gutter Brightening

Professional gutter brightening uses a specialized oxalic acid based solution (sometimes called a "gutter butter" or "elixir") that's specifically formulated to dissolve oxidation without harming the underlying paint.

The process is:

  1. Apply the brightener with a soft applicator or low-pressure sprayer
  2. Let it dwell for 30–60 seconds (depending on severity)
  3. Agitate gently with a soft brush — never abrasive
  4. Rinse with low pressure water
  5. Inspect for missed spots and repeat as needed
Why this is risky to DIY Oxalic acid is corrosive. It can damage your skin, your eyes, your landscaping, and your driveway concrete if it's not handled correctly. It also reacts differently with different paint finishes — using too strong a dilution on an older gutter can strip the paint right off. This is one we recommend leaving to a pro.

What Results Look Like

When done correctly, brightening returns the gutters to roughly 90–95% of their original color. Very old or severely oxidized gutters might come back to 80% — past a certain point, the paint itself has degraded and no chemical can recover it.

The fix lasts 2–4 years before re-staining starts. We typically recommend bundling brightening with your house soft wash to save on the trip charge.

Bundle Savings

Most of our customers do gutter brightening as part of a full exterior cleaning package. The cost difference between adding brightening to an existing soft wash vs. booking it separately is significant — usually $80–$120 less when bundled.

Check our pricing page for current bundle options, or call (336) 589-5531 for a free quote. Most jobs in the Eden, Reidsville, and Stoneville area can be scheduled within the week.

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