The Direct Answer
Because pure water dries without leaving marks, so I leave the glass to dry instead of wiping it. The water has had its minerals taken out, so nothing is left behind as it dries. Wiping would only add streaks. If the glass still looks marked once it has dried, tell me what you see.
What am I looking at when the glass is wet?
After an outside clean, your windows may look wet for a short while. That’s rinse water, and it’s pure water, so it’s still doing its job as it dries. On a dry day it clears by itself. On a damp or still day it can take longer.
It can look odd if you’re used to a cleaner who wipes the glass dry before leaving. That’s the traditional method. With pure water, wiping isn’t needed, and in fact it works against you.
Why don’t you wipe it?
With the minerals gone, there is nothing in the water to leave marks. A cloth would be touching a clean window that would have dried clear on its own, and it can leave lint or fingerprints of its own. So I leave it.
I’d rather you knew that before the first visit than after it, which is why it’s on the outside window cleaning page and in the how it works steps.
What is in tap water, and why does it matter?
Tap water carries dissolved minerals. When a drop dries on glass, the water goes and the minerals stay, and you see them as small white spots. Hard water carries more. Pure water is tap water with those minerals taken out, usually by reverse osmosis and then deionisation. I make mine in the van. Is pure water window cleaning better? goes into the detail.
What can still leave marks?
Pure water isn’t a promise that nothing can ever mark the glass. These can:
- Dirt from frames, sills and vents. It can run onto clean glass as it dries. Cleaning the frames helps cut this down (ask me about frames and sills), but nothing can promise it never happens.
- Old residue. If your windows were cleaned with soap or detergent before, residue can run out of frames and seals for the first few cleans. Spots after the first clean covers this.
- Rain. Rain can carry dirt, or wash dirt off the frames above the glass.
- Water that isn’t pure enough, or a poor rinse. Those point to a problem with the cleaning, not with your windows, so tell me if you see them.
How long should I wait before I judge it?
Give it until the glass has fully dried. On a dry day that’s usually a short while. Look at the glass from the inside, in daylight, because that shows marks best. If it’s clear, you’re done. If you can see spots or smears once it’s dry, tell me where and I’ll look at it.
Common questions
How long until it’s dry?
It depends on the weather. A mild, dry day is quicker than a damp one. It’s usually quicker on a dry, breezy day.
Can I wipe it myself if it bugs me?
You can, but you may add streaks. I’d rather you leave it and tell me if anything looks wrong afterwards.
Does it look wet at the frames longer?
Often, yes: frames and sills hold water in crevices, so those can stay damp a little longer.
Will rain straight after a clean ruin it?
Can windows be cleaned in the rain? covers weather in more detail. Not usually. Rain is soft water, so it doesn’t leave mineral spots in the way tap water does. It can carry dirt down from frames, gutters and walls, though, which is one reason I scrub frames and sills as well as the glass. If rain leaves marks you’re unhappy with, tell me and we’ll look at it.
Can I open the windows while they’re wet?
It’s best to wait until they’re dry, so water doesn’t run onto the inside sill.
What should you do next?
If your windows look wet when I leave, that’s the water drying. If you live in Wickford or Rayleigh and want to see it for yourself, get a quote and I’ll explain what to expect before the first visit.
