de-icing a vehicle

snipped-for-privacy@coolgroups.com wrote in news:0fd02603-b61e-4b3f-9559-8a5ed6e461e6 @t1g2000pra.googlegroups.com:

It will work for melting some of the ice that's on there, but the melted ice will quickly re-freeze, defeating the purpose. There's also the possibility of cracking the windshield with the thermal shock of the warm water.

Just use a common hardware-store scraper that's made for ice on car glass.

Not a great idea. Years ago A co-worker I car-pooled with poured hot water on his windshield. There was a rock chip in the windshield. After the hot water hit the windshield, it became a huge crack....

I'd suggest using a scraper, or one of the de-icing products (Preston sells one). However, until you get the windshield above the freezing point (and the dew point), ice (or fog) will continue to be a problem.

Ed

It works for a short while, then the warm water freezes and your car is icier than it was before.

Freezes even faster.

--scott

You'd need a swiming poolfull to raise the temperature of car enough to prevent your water from just become more ice on your car.

Start the engine. Turn the heater to recirc and to max. Set air to defrost only if you're sure the AC won't run (It shouldn't in the cold) Turn on the rear electric defroster.

Wait 10-15 minutes.

Cut squares in ice with an ice scraper. Scrape rest away.

Didn't you just ask about deicing too fast in another thread? And didn't you get about the same responses?

As others have said there is a risk that is the water is warm enough to do any good it might crack the window. Why don't you just use a grocery store plastic scraper. Or run the heater/defroster for a while.

For a faster warmup and faster deicing have a block heater installed.

snipped-for-privacy@panix.com (Scott Dorsey) wrote in news:fjjnul$5vo$1 @panix2.panix.com:

Buzz!!!!!!!! wrong, hot water freezes faster than cooler water. KB

WHAT? Are you nuts? What gives you this idea?

Ed

I also learned this in high school physics and did the experiments which verified it was true. The hot water starts cooling at a faster rate so it surpasses the cold water and does freeze first.

I even had to do the experiment for my Dad because he wouldn't believe. There was a considerable difference too.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

I've used hot water mainly to loosen the ice blockage in the cowl area where the wiper drop into. Pouring hot water on the glass could crack it.

On real heavy ice I use one of those brass edge ice scrappers. Its worked fine for over 20 years.

We had an ice blizzard Dec 1 in the Joliet, IL. area. The direction the rain & ice was blownig froze over the driverside doors and we had to get in throght the passengerside. Took 15-20 minutes of warming the car up before the ice come off the windshield & two fron windows. The backs I didn't bother with. The rear defroster took careof the rear window.

Next morning the Buick LF tire was flat - cut in the inner sidewall.

harryface

91 Bonneville 310,897 05 Park Avenue 64,123

Define considerable difference. I understand that under some very specific conditions you can freeze hot water faster than cold. I've even seen it domonstarted. And while this is true for carefully controlled conditions, it is definitely not the case for hot water poured on a windshield.

Usually there are several reasons cited for this apparent contradiction - cold water doesn't develope significant convection currents, so it tends to freeze at the boundry, slowing heat transfer to the rest of the water; hot water evaporates at a signnificantly higher rate, both cooling the remoning water and reducing the amount to be frozen; hot water includes less air, improving heat rransfer. None of these factors apply to hot water poured on a windshield. In that case you are dealing with a thin layer, not a pot of water.

Try this - take two identical glass jars with tops. Fill one with 40 degree water. Fill the other with 60 degree water. Seal the tops and place the jars in freezer. See which one breaks first. I'll bet you it won't be the one that started with 60 degree water. If you use open aluminum pots instead, I won't bet you.

Ed

Ed

Hot water does start cooling quicker. Thermal transfer is proportional to the current temperature difference. The bigger the difference, the more the thermal flow.

However, as soon as the hot water has cooled to being as cold as the cold water, then it cools at the same rate as the cold water cooled. But by this point, the cold water has cooled for a while already, so it's colder. The hot water never catches up. The cold water freezes first.

So the first part of the statement above is true. The second part is nonsense.

no it doesn't. It has to cool to freezing before it can freeze. What has confused you is the fact that there will be less of the hard water to freeze by the time it gets cold enough to freeze.

"In some specific circumstances, hotter water freezes faster than colder water":

I read that and followed some of it's external links. None rule out evaporation and if you fail to do so then you aren't doing a fair comparison.

Rewriting the laws of physics today are we?

I'm no skating rink expert, but I'm guessing a Zamboni uses hot water to melt the imprfections briefly and then allow them to refreeze. It probably also keeps ice from building up on the machine.

None of the specific circumstances involves pouring water onto a windshield.

Ed

C. E. White wrote: If you use open aluminum pots instead, I

It is an interesting phenomenon and yes we did use aluminum ice cube trays.

This link is a good one

I like the one theory that cold water can even supercool which hot won't do so cold water can have a lower freezing point that way, but there can be lots of reasons it would seem.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

Thanks for that link, it has really good explanations for the phenomenon.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

It is a popular notion. Sadly, it's not true. There was a good article on the subject in Scientific American back in the eighties.

--scott