Hot water - Cold glass

Has anyone cracked a window before by using really hot water in cold weather? This hasn’t happened to me but I wonder about it now that it’s colder outside. I know that drastic changes in temperature can crack glass, especially on some older single pane store fronts … I don’t want to pay for a piece of glass.

I cant be 100% positive but I think it may have something to due with the temperature inside as well. If the place is fairly warm on the inside the glass should be safe.

Also think about the Hot water ro/di machines:

I think the glass is safe.

I heard a guy did this with his windshield and it shattered. :eek:

Be careful friend.

I think Jim Willingham emailed me about this. Yes it will crack, I can’t remember the differences in temprerature to make it happen. It works both ways - hot outside & air condioning inside. And cold out/heating inside.
Mr. Squeegee can test it for us.

Maybe this topic could be discussed in an episode of weather or not. I usually don’t use water that’s extremely hot for this reason, I would rather be a little cold than pay for a huge storefront window…and it would be embarrasing as well. “Uh, yeah … Mrs. Customer I just broke your really big window b/c I’m an idiot, it is really clean though!”

All I need now is a piece of glass and this test will be a go!

I’ve also heard of tinted windows in summer having fracture stresses due to the fact that they decided to only tint one half of the glass & let natural daylight come through the other - untinted part.

I used to work for a tinting company and ran across a few of those instances as well. We never tinted half a window because of the temperature difference and expected up to 1% of applications to crack due to thermal stress. That is what got me thinking about hot water on cold glass.:cool:

I had a windshield crack in the summer. It was on my own car so I was only hurting myself. I had left the windows up and it was about 100F when I went to wash the car. The water out of the hose was extremely cold for some reason and then I heard it “CCCCCRRRAAACCCKKK”! You need quite a thermal difference for this to happen but it is possible. I’d worry most about unheated/uncooled areas that can be either very cold or very hot depending on the time of year. Single pane glass is also far more suceptable to this because of thermal transfer.

In 15 years I’ve never seen it happen.

You know, washing a car with the windows down is no treat either.

Can you elaborate? Are you insured for washing cars? Do YOU use car soap, dish soap, GG4? Do you dry with a huck, chamois or scrim?

Can you offer more than ‘no treat’ for future readers who may have need to fully understand WHY having a car washed while the windows are down is…no treat?

What kind of car? Are the windows tempered? Do you have a waiver signed? What type of interior can be washed with windows down?

Is this a ‘car wash’ or ‘at-home’ wash? Did you see Craig do it? Have your bought a car wash for your daughter? Were her windows up or down?

Is there and avatar showing windows down while being washed? Can you find a link? Is there a song or video you can provide?

Do hate-filled, right-winged, profiling Republicans do it? does the brain washing FOX new channel suggest it? Will Obama send me a check for NOT doing it? If I do it, can I get a bail out?

If Juggs does it, should he hang his client off the car roof?

Can WCR introduce a kit to ensure the windows are NOT down before washing?

Can Tony show us what it looks like in the weather?

Larry, you need to be a little more detailed.

Merry Christmas Misfits


I love how you get everything wrapped-up in one post!

Perhaps you could mention the Misfits and Christmas next time.

See recent post.

Not sure why you would want to use really hot water to wash windows with in the winter? If its to keep your hands warm then get a pair of good gloves. Hot water can crack the glass if the temperature difference is big enough and hot water evaporates faster than cold water. Also the water will only stay really hot for short period of time before it cools off.

I would use warm water to help dissolve the soap and and a little methyl hydrate (alcohol) if it was freezing up on me.


We use a hot water system for wfp work year round.

The biggest issue with breaking glass is if it happens to be non-insulated or if the heat inside the building is off.

Insulated glass panes have air between them that is typically a lot warmer then the cold outside temps.

We have used 140 degree water on days with 30 degree outside temps with no problems.

The fact that hot water evaporates faster then cold is actually a benefit in this scenario as it is able to dry before freezing.

I don’t know if this is a sickness or a talent, but you are one funny dude!

I think Phil will say it’s both.:wink:

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What I can tell you is from my own experience. Only thing was it was with a car. There were 3 of us in the car, it was dead winter, snow on the ground. We stopped at the front passengers house for something, I can’t remember (this is 20 years ago). I was sitting in the back behind the driver. When the guy came out of the home he tought it would be funny to toss cold water on the back window. He runs out, almost breaks his ass on ice, tosses the water right at me. If there were no window the water would have hit me in the face. BAMMM! The entire window shatters and drops to the seat. The driver, seeing it was only water. Freaks out on ME!!! lol. Thinking I “MUST HAVE DONE SOMETHING!!”. I never touched the window. It freaked me out just as much as the driver. The car was hot as hell inside. I remember I had my jacket off. And we had the windows rolled up. Freaked me out. But I saw it with my own eyes. :eek: My friend said it was just water from the tap. Cold…