If your house was just washed and the gutters still wear evenly spaced black vertical streaks, nothing went wrong — tiger striping simply is not dirt. It is oxidation bonded to the aluminium, and removing it is the ‘brightening’ half of gutter cleaning and brightening.
What the stripes are made of
Rainwater sheeting over the gutter lip carries shingle residue, atmospheric pollution and organic particles. Where it runs down the face, it reacts with the aluminium’s oxidising surface and the factory paint, forming an electrostatically bonded stain in the drip pattern — hence the tiger stripes.
Because the bond is chemical, detergents and soft-wash solutions clean around the striping and leave it intact. That is why freshly washed houses so often still look tired at the roofline.
The spacing is not random either. Water leaves a roof edge in a rhythm set by the shingle courses, small irregularities in the drip edge and the fall of the run, so each rivulet lands on more or less the same inch of gutter face every time it rains. The inside of the trough gets flooded and drained; the face gets a thin film that clings, dries slowly and leaves everything it was carrying behind. That difference in how the water behaves is why the outside stains and the inside does not.
Why a house wash walks straight past them
Soft-wash chemistry is built to kill biology. It works on algae, mildew and mould because those are living colonies with organic pigment, and the solution both kills the organism and bleaches what it leaves behind. Tiger striping is not alive and has no organic pigment to bleach. You can hold the same mix on it for as long as you like and the stripe will still be there when you rinse.
There is a second, more annoying effect. A good house wash lifts the siding several shades. The gutters do not move at all. The contrast that was there the whole time suddenly reads clearly from the street, which is why people so often ring up after a wash convinced the gutters were somehow made worse. They were not. The reference point moved.
Clearing, flushing and brightening are three different jobs
They get lumped together as “gutter cleaning” and they are not the same work, do not take the same time, and do not fix the same problem.
Clearing
Removing the debris from inside the trough by hand and bagging it. This is what protects the fascia and the foundation, and it is the job that actually has to happen on a schedule — how often depends almost entirely on the trees over the roof.
Flushing
Running water down the cleared run to prove it carries. A gutter that looks empty can still be useless if the downspout is packed or the underground drain it feeds is silted up. Flushing is also when the fall gets checked — a gutter should have a slight continuous drop toward the outlet, typically in the order of a quarter of an inch over every ten feet, and hangers should be spaced closely enough that no section can sag between them. Water standing in a level or back-pitched section is a problem you can see in five seconds and would otherwise not know about for years.
Brightening
The exterior face only. Nothing to do with flow, everything to do with how the roofline reads. It is cosmetic work, and it is honest to call it that.
What brightening involves
A dedicated gutter brightener — typically a butyl-based or similar cleaner formulated for oxidation — is applied to the face, agitated, and rinsed before it can dry. It is real labour, linear foot by linear foot, which is why it is quoted as its own line rather than absorbed into a house wash.
The result is usually striking: gutters go from streaked grey to something close to their original white, and the whole roofline reads a decade newer.
In practice the run is worked in short sections so the product never dries on the surface, because a brightener that dries can leave its own marking. Anything below the work gets wet down first — siding, windows, shrubs — and rinsed again after. The agitation matters as much as the chemistry: the bond is mechanical as well as chemical at that point, and a soft brush on a pole is what breaks it. That is also why a two-storey run costs more than a single-storey run of the same length. Reach is most of the labour.
The order matters too. Brightening is done as part of, or immediately after, the house wash — never before, because rinse water off the siding runs straight down the freshly brightened face.
The limits worth knowing
Brightening removes oxidation staining; it does not repaint. Where the factory finish itself has failed — peeling, chalking through to bare metal — the brightener reveals clean but worn paint. On old, heavily weathered gutters the honest outcome is ‘much better’, not ‘new’.
We will tell you which category yours are in before we start, because the difference matters to whether the spend is worth it.
You can run the test yourself. Rub a dry thumb firmly along the gutter face. If it comes away with a chalky white film, the paint’s binder has broken down and you are looking at the powdered remains of the coating rather than a film sitting on top of it. No cleaner restores a failed binder. Brightening a chalked gutter still improves it, but it reads slightly flat and it re-soils faster. Where you see white pitting or a rough bloom in the metal itself, that is corrosion under the coating, and it is permanent. That is the honest ceiling.
Tiger striping in Southeast Missouri
Two regional conditions make striping here worse than it would be in a drier climate. The first is how long a film stays wet. River-valley damp and morning fog through the Cape Girardeau and Perryville bottoms mean the water sheeting off a roof at dawn is still sitting on the gutter face hours later, and slow drying is exactly what lets a deposit settle and bond rather than run off.
The second is what the water is carrying. Mature oak and pine cover over most properties around Patton and Marble Hill puts tannin-rich leaf litter in the trough and a steady drift of pollen and seed fluff over the lip every spring. Tannin staining looks similar to oxidation from the ground — brown-black, vertical — but it is a different animal and it often lifts far more easily, which is worth knowing before you assume the worst. Houses on gravel roads add a fine limestone dust that binds into the same film; farmhouses set back from the blacktop routinely stripe faster than a house of the same age in town.
Well water is worth a word. Where a sprinkler or a hose bib on iron-rich well water throws spray up onto a low gutter run, you can get an orange cast on the face that has nothing to do with oxidation at all. That is a mineral stain and it responds to different chemistry — the same problem that puts orange stains on driveways all over this region. Diagnosing it correctly is the difference between a fix and a wasted afternoon.
Gutters on the shaded north and east elevations stripe first and worst here, for the same reason the north wall of a house always greens first: less sun, longer drying times, more hours wet per year.
Common questions
Will brightening damage the paint on my gutters?
Not on sound factory finish, when the product is kept wet, worked in sections and rinsed properly. The risk is in the misuse — letting a brightener dry on the surface, or leaving it on far longer than it needs. On coatings that have already chalked, brightening does not damage anything but it can reveal how far gone the paint already was.
Can I just do this myself with a household cleaner?
Household detergent will not touch it, for the same reason a house wash does not. People do get results with dedicated gutter brighteners bought retail. The two things that go wrong are ladder work over a whole run, which is where the real risk sits, and letting product dry on hot aluminium in the sun.
Do the stripes come back?
Yes, slowly. Oxidation is an ongoing process and the same rain lands on the same face. On sound paint you would expect to want it again in a few years rather than annually. On a chalked finish it returns noticeably faster.
Does brightening clean the inside of the gutter too?
No. Those are separate jobs with separate purposes. Brightening the face does nothing for flow, and clearing the trough does nothing for the stripes. Most people book them together because the equipment is already on site, but you can have either on its own.
My gutters are steel, not aluminium. Is it the same?
The staining pattern is similar but the risk profile is not. Older galvanised steel runs can have rust breaking through at the seams and end caps, and cleaning agents on exposed steel need more care. Send a close photo of a seam and we will tell you what you have before anything is quoted.
Should I brighten gutters that are about to be replaced?
No. If a run is sagging, leaking at the seams or hanging off rotten timber, the money belongs in the repair. Cleaning a failing gutter buys appearance, not time — and we will say so rather than take the work.
If the stripes are what bothers you, say so when you book — it is a separate step and we will quote it properly. Read more about gutter cleaning and brightening →