A streak is not leftover dirt. It is a thin film of something dissolved in your cleaning water, drying in place. Soap, tap-water minerals, or the film itself flashing dry before you pull it off. Three fixes cover almost every case, and one common streak cannot be fixed at all.
Wipe a genuinely clean pane with a dry cloth and it stays clean. Streaks appear because something stayed on the glass and then dried, and dried film scatters light in lines. There are only three things it can be. Soap, because surfactants are engineered to stay on a surface. Dissolved minerals, because tap water across the Treasure Valley carries roughly 150 to 350 parts per million of calcium, magnesium, sodium and silica, all of which stay behind when the water leaves. Or the film itself, because you did not physically remove all of it before it evaporated. Newspaper, vinegar and buffing harder are attempts to hide one of those three. The fixes below remove them instead. Run one diagnostic first: clean the outside with horizontal strokes and the inside with vertical ones. The direction of the streak tells you which side of the glass to work on, and about a third of the time the answer is the side you already cleaned.
Almost everyone uses ten to fifty times more detergent than the job needs. A working professional mix is about a quarter teaspoon of dish soap in a gallon of water, roughly one milliliter, which is enough to lubricate a squeegee blade and nothing more. Soap is not the cleaner here. It is a lubricant and a wetting agent, and every molecule you add is a molecule that has to be physically dragged off the pane. Blue ammonia sprays fail for a related reason: they carry surfactants and glycol ethers that evaporate at different speeds, so the pane dries unevenly even when it is chemically clean. Ammonia also degrades aftermarket window film, which sits on a lot of west-facing Idaho glass. Then there is the quiet one nobody checks. If you wash your microfiber with fabric softener or dry it with dryer sheets, the cloth is coated in cationic surfactant and will streak every window it touches. Wash them alone, hot, no softener, no sheets.
The film has to come off wet. Once it starts to flash dry you are no longer cleaning, you are pushing residue around. Glass in direct sun runs 30 to 40 degrees hotter than the air, so a 90 degree July afternoon in Meridian puts the pane near 125 and your solution is gone in under fifteen seconds. Work the shaded side of the house and follow the shade around, or start before nine in the morning. On a hot day, wet and pull one pane at a time instead of soaping an entire slider. The cold end matters too. Below about 40 degrees F the solution thickens and the blade drags, and below freezing it sheets ice onto the glass and your walkway. Late September into October and April into May are the forgiving windows here. Last piece: flip or replace your squeegee rubber. One nick leaves a line on every pass, and a blade rounds over after roughly eight hours of real use.
Even a clean squeegee pull leaves water at the edges and in the corners, and that water dries into the frame line most people call a streak. Two ways to kill it. The cheap way is to detail the perimeter with a dry waffle-weave microfiber immediately after each pane, keeping a separate towel for wiping the blade so you are not dragging dirty water back onto glass. The better way is to stop using tap water for the last contact. A gallon of distilled water reads 0 to 1 ppm and costs about $1.50 at any grocery store in the valley, and one gallon detail-rinses a whole ground floor. Rinse or wipe with distilled and there is nothing left to dry into a line. That is the same principle behind professional pure-water systems, done by hand. Do not skip frames and tracks. Dirty water parked in a track wicks back onto clean glass the next time it rains.
Some of what gets called streaking is damage, and no technique or product removes it. Hard-water spotting from years of sprinkler overspray starts as a deposit sitting on the glass and slowly reacts into it. Early film comes off with an acidic gel or a cerium oxide polish, which is a restoration job rather than a cleaning. Once it has etched, the marks are physically in the pane, and the honest answers are living with it or replacing the glass. Nobody polishes that out at any price, and we will say so before we charge you anything. Haze that does not change no matter which side you wipe is usually a failed seal in a double-pane unit, and it sits between the panes where nothing reaches. And if marks return within two weeks in the same fan-shaped arc, that is a sprinkler head. Rotating it ten degrees is free and fixes more than any service you can buy.
Here is the part that costs us work. If you have a single-story house and every pane is reachable from the ground, DIY is the right call. A 14-inch squeegee, a T-bar washer, a bucket and two waffle towels run about $50 to $70 once, and with the three fixes above the finish is hard to tell from ours. Do not pay $199 to solve a problem a $6 run of distilled water solves. Call someone when the glass is above a ladder you are not comfortable on, when there are more panes than a Saturday holds, or when frames, tracks and screens need attention a squeegee cannot give. That is what our pure-water setup is for, and it is why the finish sheds the next rain instead of spotting. Cleaning starts at $199 by pane count, screens add $50, and the Quarterly membership saves $100 per cleaning with no contract. If your only problem is one etched shower door, do not book a window cleaning.
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Partly. The acetic acid dissolves light mineral film, so vinegar helps on hard-water haze. It does nothing for soap residue, and on glass that still carries old detergent it will smear. If you use it, run roughly one part vinegar to four parts water, work the pane, then rinse with clean water and squeegee it off. Vinegar left to air dry is just another film. Keep it off stone sills and untreated wood.
Newspaper is denser and lints far less than a paper towel, which is why the trick survived. But it is a workaround for using too much soap, and modern soy-ink newsprint is thinner than it was decades ago and tears once it is wet. A four-dollar waffle-weave microfiber outperforms it and lasts years. Paper towels are the actual culprit: they shed fiber onto the glass, and that fiber is what you see catching the light.
Usually not. Distilled runs about $1.50 a gallon and a full house exterior can drink 40 to 60 gallons, so that gets expensive fast. Use tap water for washing and scrubbing, where lifting soil is the only thing that matters, and save distilled for the final rinse or the edge detail, which is where mineral spotting actually forms. One gallon covers the ground floor of most homes.
Clean rain is close to distilled, near zero dissolved solids, so the rain itself does not spot. What spots is what it collects on the way down: roof grit, dust off the frames, and whatever residue was already sitting on the pane. Streaks that appear after rain almost always mean soap or mineral film was there first, and the water re-dissolved it and dried it back down in runs.
Flip it when it stops pulling clean, and replace it when both edges are rounded or nicked. In steady professional use that is every one to two days per side. A homeowner doing their own house a few times a year gets a season or two out of a blade, but check the edge with a fingernail before you start. A single nick puts a line on every pane you touch. Replacement rubber costs about $5.
The streak itself is residue and washes off. The damage comes from what people reach for to remove it. Razor blades on tempered glass can drag fabrication debris and leave permanent scratch trails, scouring pads dull the surface, and abrasive powders scratch outright. If a mark will not come off with light soap and a clean squeegee, stop and identify what it is before escalating to anything harder.
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