You followed the instructions. You bought the "streak-free" cleaner. You watched the videos. You spent an hour on a Saturday morning carefully cleaning every window in the house.
Then the afternoon sun came through and there they were. Streaks. Everywhere.
If this keeps happening to you, the problem isn't effort. It's not bad luck. And it's almost certainly not the glass itself.
After 25 years of cleaning windows professionally — from residential homes in Melbourne to high-rise buildings in Vienna — I can diagnose window streaks the way a mechanic diagnoses engine noise. And in almost every case, the cause is one of seven things that nobody talks about.
Let's figure out exactly what's going wrong.
Cause #1: You're Using the Wrong Cleaner (And It's Not What You Think)
This is the most common cause and the hardest to accept: your "streak-free" glass cleaner is probably creating the streaks.
Commercial glass cleaners contain surfactants, ammonia, or alcohol-based chemicals that dissolve dirt effectively. The problem is what they leave behind. These chemicals create a thin residue layer on the glass. When the cleaner evaporates, the residue stays — and that's what you see as streaks when the light hits.
The fix is almost embarrassingly simple: a few drops of dish soap in a bucket of water. That's it. Dish soap breaks down grease and oils without leaving chemical residue. It's what I've used professionally for 25 years, and it's what every experienced window cleaner I know uses.
Not a capful. Not a squeeze. A few drops. If you see foam, you've used too much — and too much soap is cause #2.
Cause #2: Too Much Soap
More soap does not mean cleaner windows. This is maybe the hardest habit to break.
Excess soap creates a film on the glass that the squeegee can't fully remove. You don't see it immediately because it's transparent when wet. But as it dries, it becomes visible — a hazy, streaky film that catches every ray of light.
Here's my test: dip your scrubber in the bucket and squeeze it out. You should see slight bubbles in the water. If you see thick foam sitting on top, pour some water out, add fresh water, and try again. The ratio should be barely-there — just enough soap to cut through fingerprints and oils.
If you've already cleaned with too much soap, you'll need to go over the windows again with clean water to remove the soap residue. I know that's frustrating. But layering more cleaner on top of soap residue makes it worse, not better.
"The Window Cleaning Manifesto" →
Cause #3: Your Water Is Working Against You
This one surprises people every time.
If your tap water has high mineral content — calcium, magnesium, iron — those minerals don't evaporate when water dries. They stay on the glass as white spots, cloudy film, or chalky streaks. No amount of wiping removes them because they're not on the surface. They're deposited into the microscopic texture of the glass.
You can test this in 30 seconds: wet a small section of a window with tap water and let it air dry. If you see white spots or cloudiness, your water is the problem.
Three solutions, from easiest to most thorough:
Add white vinegar to your cleaning solution — 1 part vinegar to 3 parts water. The acid dissolves mineral deposits that soap can't touch.
Use distilled water for the final squeegee pass. Scrub with tap water to loosen dirt, but squeegee with distilled. A bottle costs about $1 and does 10+ windows.
If you're in a hard water area and you clean windows regularly, a water softener solves this permanently.
Cause #4: You're Cleaning in Direct Sunlight
Every professional window cleaner knows this rule. Most homeowners have never heard it.
When sunlight hits wet glass, the cleaning solution evaporates faster than you can squeegee it off. The dissolved dirt and soap residue get "baked" onto the glass surface. The result: streaks that are actually harder to remove than the original dirt.
This is why professional window cleaners check the weather forecast before scheduling jobs. We plan around cloud cover. It matters that much.
The best time to clean windows: overcast days, or early morning before the sun reaches your windows. If you must clean on a sunny day, work on the shaded side of your house first and follow the shade around as the day progresses.
One more thing about temperature: don't clean windows when it's below 40°F (5°C). The solution doesn't spread properly in extreme cold, and you'll fight the tools instead of using them.
Cause #5: You're Using the Wrong Tools
I need to be direct about this one.
Paper towels leave streaks. Always. Without exception. They break down when wet and deposit tiny fibers on the glass. Those fibers catch light and look like streaks or lint marks. It doesn't matter which brand you buy.
Newspapers — the old grandmother trick — work better than paper towels, but they leave ink residue on your hands and frames, and they're inconsistent depending on the paper quality.
Cotton cloths and old t-shirts leave fabric fibers that are invisible when the glass is wet but visible when dry.
What actually works is a three-tool system:
A scrubber (microfiber sleeve) to apply solution and loosen dirt. This does the actual cleaning.
A professional squeegee with a sharp rubber blade to remove water in one motion. This prevents streaks by removing all liquid before it can dry.
A lint-free microfiber cloth for edge detailing only — not for the main cleaning.
If you're using a spray bottle and paper towels, you're using a system designed to sell cleaning products, not to clean windows. I wrote a complete guide to professional step-by-step technique if you want the full method.
Cause #6: Your Squeegee Technique Is Off
Even with the right tools, technique matters more than most people expect.
The three most common squeegee mistakes I see:
Wrong angle. The squeegee blade needs to contact the glass at roughly 45 degrees. Too steep and it skips over water. Too flat and it pushes water sideways instead of collecting it. The angle creates a "wave" of water in front of the blade that carries dirt to the edge.
Stopping mid-stroke. Every time you stop and restart, you create a wet line that dries at a different rate than the surrounding area. That's a streak. Professional technique means smooth, continuous strokes across the full width or height of the pane.
Not wiping the blade between passes. After each stroke, the blade has dirty water on it. If you start the next stroke without wiping the blade clean, you're depositing that dirty water back onto clean glass. One wipe with your detail cloth after every pass. Every single time.
This is why squeegee technique is a physical skill, not just knowledge. You can understand the theory perfectly and still get streaks until your hands learn the motion. It's muscle memory — the same way you can't learn to ride a bike by reading about it.
That's exactly why I built the AR Window Cleaning Training Tool. It lets you practice the technique and see your movements in real-time without needing real windows. Most beginners need about 15 practice windows before the motion feels natural. With AR, you can do that in an afternoon.
"AR Window Cleaning Training Tool" →
Cause #7: You're Detailing Wrong (Or Not At All)
The last 10% of the job creates 90% of the visible streaks.
After squeegeeing, there's always a thin line of water along the edges where the blade can't reach — top, bottom, sides, and especially corners. If you leave it, that water runs down onto your clean glass and creates drip streaks.
The fix: one pass with a lint-free microfiber cloth along each edge. Not back-and-forth rubbing — that creates static and attracts dust. One smooth wipe per edge.
Most people either skip this step entirely (leaving edge drips) or over-do it by wiping the entire window with a cloth (which redistributes water and creates new streaks). The detail cloth is for edges and corners only. The squeegee does the main surface.
The Quick Diagnosis: Find Your Problem in 60 Seconds
Next time you get streaks, look at them carefully. They tell you exactly what went wrong:
Streaks that appear everywhere, even distribution: Too much soap, or wrong cleaner. Clean again with less soap.
White spots or cloudy film: Hard water minerals. Add vinegar or use distilled water.
Streaks that appear quickly after cleaning: Sunlight evaporation. Wait for cloud cover or shade.
Tiny fiber marks visible in sunlight: Paper towels or cotton cloth. Switch to squeegee + microfiber.
Lines running vertically from the top: Edge water dripping down. Detail your edges after squeegeeing.
Random streaks in no pattern: Dirty squeegee blade. Wipe between passes or replace worn rubber.
The Real Fix Is Simpler Than You Think
Here's what I want you to take from this: streaks aren't a mystery. They have specific, diagnosable causes. And once you identify your cause, the fix is usually straightforward and costs almost nothing.
You don't need expensive products. You don't need a professional to come out. You need the right technique with the right tools.
I've spent 25 years figuring this out so you don't have to. Every window I've ever cleaned — from Geoffrey Rush's windows in Melbourne to centuries-old glass in Vienna — follows the same principles. Simple soap, proper tools, correct technique.
If you want to master the full technique from start to finish, my free Window Cleaning Manifesto covers everything in under 5 minutes. Watch it, clean one window, and see the difference for yourself.
The streaks end here.
Ready to Eliminate Streaks Permanently?
Download "The Window Cleaning Manifesto" — my FREE 5-minute training that gives you the professional technique behind streak-free windows. No expensive products. Just the method that works.
About the Author:
Justin Orloff is a professional window cleaner with 25+ years of experience, based in Vienna, Austria. He created the world's first AR window cleaning training platform, serving Clear View Creators in 15+ countries. Justin started cleaning windows professionally in Melbourne, Australia in 1999 and has worked on everything from soaring skyscrapers to cozy family homes.
