Does anyone else use warm water to defrost cars? - theterranaut
Or is it just me? I see my neighbours looking at me as if I'm mad, but I've done this ever since I had a driving licence. Beats standing there with a scraper, or spraying toxic chemicals all over the place. There seems to be an urban myth that the screen will shatter, and perhaps it would with boiling water, but I find that even tepid water will do the trick.

Anyone else?

tt
Does anyone else use warm water to defrost cars? - maximus
Me as well. I use water at room temperature-I leave it in the hall. Apart from the quick getaway you also get the benefit of less interior misting, due to the fact that you've raised the glass temperature. The only time I've had a problem is when its very very cold and the water has started to freeze on screen.
Does anyone else use warm water to defrost cars? - R75
Yep, I do exactly the same, keep an empty 4pt milk container handy for it. Takes 30 seconds and does all the windows,watch the neighbours scraping away and freezing their hands!!! Only ever use luke warm water from the tap though.
Does anyone else use warm water to defrost cars? - NowWheels
Me too. Bucket of tepid water filled in the sink (mostly cold, but with a bit of hot to bring it up to about 25C), sloshed on the car -- saves lots of scraping. Need to move off soon after, though, else the water freezes up again.
Does anyone else use warm water to defrost cars? - craig-pd130
As R75 above -- hand-hot water from the tap into a 2 litre container, pour on windows, then (in really cold weather) squeegee the excess off so it doesn't re-freeze.

Clear windows in no time and it also gets rid of "mist" on the inside too.
Does anyone else use warm water to defrost cars? - Devolution
With most thicker modern windscreens it is less likely they will crack but still possible, even with tepid water if you already have a weak spot such as a stone chip or crack.
Bearing in mind warm water freezes faster than cold water so as said above be ready to wipe away any excess.
Does anyone else use warm water to defrost cars? - Robin Reliant

> Bearing in mind warm water freezes faster than cold water

How?
Does anyone else use warm water to defrost cars? - NowWheels
Bearing in mind warm water freezes faster than cold water


Have the laws of physics been rewritten since I was at school?
Does anyone else use warm water to defrost cars? - GroovyMucker
>> Bearing in mind warm water freezes faster than cold water
Have the laws of physics been rewritten since I was at school?


It's true, I think, but I can't remember the explanation off-hand.

Maybe I'll trawl the internet. That's a good source of reliable information.

Evaporation?

Edited by GroovyMucker on 29/11/2008 at 13:44

Does anyone else use warm water to defrost cars? - OldSock
I think what you mean is that the instantaneous rate of cooling is higher with hotter water......
Does anyone else use warm water to defrost cars? - Dynamic Dave
It's true I think but I can't remember the explanation off-hand.


Found via a forum search:

www.weburbia.com/physics/hot_water.html

Does anyone else use warm water to defrost cars? - Ian (Cape Town)
Ok, here we go!

"If the container is sitting on a layer of frost which conducts heat poorly, the hot water may melt that layer of frost, and thus establish a better cooling system in the long run. Obviously explanations like this are not very general, since most experiments are not done with containers sitting on layers of frost."

Precisely.
I remember my granny had metal ice-cube trays, which were only ever used when us kids turned up at her place twice yearly, and THEY melted through the layers of frost in her fridge (When filled with hot water), and froze better, due to the surrounding of frost, and direct metal-to-metal contact with the metal box of her freezer compartment.

Just a theory.



Does anyone else use warm water to defrost cars? - john farrar
It's called the "Mpemba Effect" and has been scientifically proven when cosidering water with some depth in a container. Whether it would apply to a thin film is doubtful.
Does anyone else use warm water to defrost cars? - the swiss tony
en.wikipedia.org/wiki/Mpemba_effect

Good old Wiki!

my own theory is that the steam freezes 1st as is less dense, then the resulting crust aids heat transference. the one time I tried defrosting my windows using the warm water method I found I ended up in bigger trouble as the water I used seemed to freeze harder than the existing ice.
It can also cause problems getting in the car, i.e. water in the lock barrel, or freezing the door against the door seals.
Does anyone else use warm water to defrost cars? - Manatee
Have the laws of physics been rewritten since I was at school?


Yes. You're perhaps thinking that you need to remove one calorie from each gram of water for every degree K that its temperature is higher than the freezing point, and then a further 80 or so from each gram before it changes state; therefore it takes longer to freeze warmer water than colder. The premise of this reasoning is still correct, but the conclusion is wrong.

Since our school days, it has been discovered that there is a kind of momentum gathered as the temperature of the water falls. You start off with tap water at say 50 degrees C, and throw it on a freezing car. it cools so rapidly that when it gets to zero it doesn't stop cooling, it carries right on.

Note that the first law of thermodynamics has not been repealed; and it does require the transfer of extra heat into the water to freeze it more quickly than cold water via this newly discovered 'Momentum of Heat Transfer' - consequently the vehicle itself must donate more heat, and instead of warming up and levelling out the temperature gradient as you might expect, it can actually get colder than the ambient temperature for a short period of time - long enough to freeze the water!

Now you might be asking, why doesn't the Momentum of Heat Transfer theory apply to the car itself and cause it to heat more quickly, rather than to get even colder? Simple - the theory only operates with cooling, liquid H2O. This is lucky for us as otherwise the temperature oscillations set up in all manner of thermodynamic applications would cause havoc and would certainly render internal combustion engines inoperable - and there would be no back room.

On the other hand, it could be what Devolution says...

Edited by Manatee on 29/11/2008 at 14:03

Does anyone else use warm water to defrost cars? - GroovyMucker
Note that the first law of thermodynamics has not been repealed


ie ye canna change the laws of physics

Does anyone else use warm water to defrost cars? - oldgit
>> Bearing in mind warm water freezes faster than cold water
Have the laws of physics been rewritten since I was at school?


This phenomenon may be due to the fact that warm/hot water is lower in viscosity and, more importantly, has a lower Surface Tension thus resulting in a much thinner film left which may then refreeze more quickly.
Does anyone else use warm water to defrost cars? - adverse camber
Newtons cooling curves.

Rate of temperature fall is proportional to the temperature difference between the water and its suroundings. Its why adding milk at once to your coffee keeps it warmer than leaving it.
Does anyone else use warm water to defrost cars? - OldSock
If it's done off the road then not a problem, but I'd take issue with this practice if not.

Leaving a large patch of water to re-freeze on the road is a hazard to both motorists and pedestrians alike.
Does anyone else use warm water to defrost cars? - theterranaut
OldSock- I find a kettleful is more than enough, but take your point that it's important to watch where you do this.
Does anyone else use warm water to defrost cars? - Devolution
Get 2 ice cube trays, fill one with boiling water and one with cold tap water then put into the freezer.

The one with boiling water will freeze into ice cubes first. As said the rate of cooling is much quicker so causes it to freeze much faster.

tinyurl.com/2s3u6e

Edited by Devolution on 29/11/2008 at 13:48

Does anyone else use warm water to defrost cars? - Hamsafar
Yes, I do it too, just above body temperature, maybe 30degC.
The more you use, the higher temperature the glass will reach and so it will stay warm for longer preventing refreeze or interior misting until the car's de-mister gets up to temperature.

Also it beats the canned de-icer, as this reduces the temperature of the glass during the process of melting the ice. So a screen at -1degC with ice and frost on it can become -10degC after de-icing and so condensation rapidly forms and freezes on it.

If you want to prove it, put a load of ice cubes and water in a pint glass, and then add some deicer/salt/antifreeze and you will see it goes down to as low as -20degC and ice will form on the outside of the glass. I can't remember the name of the effect but it is to do with the energy required to change the state of the solid to a liquid (enthalpy) and the only energy available being in the glass.

Edited by Hamsafar on 29/11/2008 at 14:00

Does anyone else use warm water to defrost cars? - Altea Ego
yup, warm water from the tap, into a large jug, front rear and side screens, and off we go.
Does anyone else use warm water to defrost cars? - b308
And me!

Perhaps we should have asked if anyone do it?! :)
Does anyone else use warm water to defrost cars? - RobertyBob
Yes, another vote here for tipping a jug of cool water over frozen windows.

Having said that, I found that taking early retirement and so avoiding most of those early morning starts a much better idea. :-)
Does anyone else use warm water to defrost cars? - b308
Should have been:
Perhaps we should have asked if anyone doesn't do it?! :)
Does anyone else use warm water to defrost cars? - oldgit
>>.............
If you want to prove it put a load of ice cubes and water in
a pint glass and then add some deicer/salt/antifreeze and you will see it goes down
to as low as -20degC and ice will form on the outside of the glass.
I can't remember the name of the effect but it is to do with the
energy required to change the state of the solid to a liquid (enthalpy) and the
only energy available being in the glass.


This mixture formed is a Eutectic mixture.
Does anyone else use warm water to defrost cars? - CGNorwich
The one with boiling water will freeze into ice cubes first. As said the rate of cooling is much quicker so causes it to freeze much faster.

Tried it. It's wrong - The cold water froze first.
Does anyone else use warm water to defrost cars? - L'escargot
Start engine, switch on front and rear screen electrical heaters, set heater to maximum heat; all air to screen and maximum fan speed. By the time I've scraped the glass any residual frost on front and rear screens has melted and I can jump in, operate the wipers, and drive off. No faffing about filling a water container and taking it in and out of the house.
Does anyone else use warm water to defrost cars? - Bromptonaut
Engine on, max defrost and hrw then apply warm water to front and sides. Ice gone and none of the internal misting associated with chemical de-ice.

The pain is when it freezes all day and the car's frozen up on the station car park.
Does anyone else use warm water to defrost cars? - 1400ted
The pain is when it freezes all day and the car's frozen up on the station car park.
Simple, buy a large cheap thermos and take it with you full of hot water. Leave it in the car and it will be just right at 'going home' time
Ted
Does anyone else use warm water to defrost cars? - Stuartli
I've used the tepid water method for many, many years when necessary - fortunately living on the NW Coast means that temperatures are normally a bit higher than inland, whilst the car being parked and thus sheltered to some extent on the south side of the house also helps.
Does anyone else use warm water to defrost cars? - craig-pd130

As a footnote, often while I would be doing my warm water routine, a next-door neighbour used to come out, start both his and his wife's car, set blowers on full and heated screens on, then go back inside, leaving both cars at fast idle for 5+ minutes ... then would still have to scrape the side windows clear when he came out again.

I used to feel quite annoyed at a) the waste of fuel, b) the unnecessary pollution and c) the damage to the engines of both cars this would do.
Does anyone else use warm water to defrost cars? - bazza
I have a whole street of neighbours who do this! There's some seriously valuable tackle available in my street if only those types knew about it ! I may one day sneak out, pinch all the keys and wait for the show to begin....!
Does anyone else use warm water to defrost cars? - Stuartli
>>..then go back inside..>>

A friend of mine did this a while back and discovered on his return a few minutes later that his Focus had disappeared...

It turned up in the Liverpool area.


Does anyone else use warm water to defrost cars? - Devolution
Isn't there something where you are not supposed to leave a running car unattended anyway? At least not on the public road I imagine. I don't know where you stand with those "remote start" kits you can fit to cars...
Does anyone else use warm water to defrost cars? - sony
I use my garage. No hot water or scraper needed!
Does anyone else use warm water to defrost cars? - Dynamic Dave
I use my garage. No hot water or scraper needed!


Ditto. I also don't put the heater on until the temperature gauge starts moving. That way the engine warms up quicker, and so does the passenger compartment.
Does anyone else use warm water to defrost cars? - Ian (Cape Town)
Probably illegal, Devo.

Off on a tangent, same with the kits you can fit to let your Turbo cool down for 5 minutes - as advertised in certain motoring-for-chavs magazines...
Does anyone else use warm water to defrost cars? - oldnotbold
I cover the car in a large piece of an old sail. Can't be doing with too much physical effort so soon after getting up.
Does anyone else use warm water to defrost cars? - Lygonos
Tepid water works perfectly, but I'd be careful if it is insanely cold (eg. -20c).

Also, be wary of using it on your doors - if it is very cold the water can de-ice the door window, but the water that makes its way past the window seal and into the door can freeze up the locking mechanism if it re-ices.

(Personal experience! 2am outside a big cinema unable to get the drivers door lock to close until I'd been running the car/heater 15mins to warm up the doors, after using a big bottle of water to deice the door glass...)
Does anyone else use warm water to defrost cars? - Peter D
Every year the same topic regarding defrosting in the mornings. As has been mentioned the container of water left in the hall/utility room is the way to go. Tepid even warm water can crack a screen. I have never scraped a screen in my life. Wolud you rub road grit into your bathroom mirror. I live in Scotland and is by location usually colder. Regards Peter
Does anyone else use warm water to defrost cars? - theterranaut
Sorry Peter- a forum search revealed zilch, and I haven't been around here all that long.
I too live in Scotland- great, innit?

:)

tt
Does anyone else use warm water to defrost cars? - jbif
Sorry Peter- a forum search revealed zilch


theterranaut:

1) forum search: defrosting windscreens; time 1 year;
produces many threads.

2) forum search: frost ice warm water; time 1 year;
produces many threads.


Nowwheels >>"Have the laws of physics been rewritten since I was at school?" :

3) forum search: hot water freezes quicker; time >1 year; produces this thread
www.honestjohn.co.uk/forum/post/index.htm?v=e&t=27...3
Hot water freezes quicker than cold (!) - L'escargot Mon 20 Dec 04 09:04
"A non-scientific friend of mine insists that hot water freezes quicker than cold. My science education tells me that this theory is against all the rules of nature, and is merely an old wives' tale. "



Edited by jbif on 30/11/2008 at 11:46

Does anyone else use warm water to defrost cars? - anthonyf
If your locks are frozen use your own built in warm water spout - if you are a chap that is. If not ask a friend to help. Tip from an AA man!
Does anyone else use warm water to defrost cars? - Stuartli
>>.. to leave a running car unattended anyway?
At least not on the public road I imagine. ...?>>

It is most definitely illegal on a public road.
Does anyone else use warm water to defrost cars? - Robin Reliant
I suppose that if one is in a hurry a liquid stored at body temperature would be an effective de-icer?
Does anyone else use warm water to defrost cars? - Altea Ego
I suppose that if one is in a hurry a liquid stored at body temperature
would be an effective de-icer?


except in a vw where the pollen filter is leaking. You then get "liquid stored at body temperature" in the footwell.

not nice



Does anyone else use warm water to defrost cars? - craig-pd130

Also contains salts to ensure it doesn't re-freeze ;-)
Does anyone else use warm water to defrost cars? - Alby Back
Defrosting procedures.

1/ Get someone else to do it while you are in the shower

2/ Wait for car to defrost naturally before driving ( this has the side benefit of avoiding rush hour traffic )

3/ If options 1 or 2 are not available, make a mug of tea, obtain a packet of cigarettes and a lighter, go outside, switch on engine and lean on something suitable while drinking the tea and smoking. Unless it is a particularly hard frost the job will have taken care of itself by the time the tea and stogie are finished.
Does anyone else use warm water to defrost cars? - DP
I've used tepid water for years and never had a screen crack yet.

I did once get a roasting from a neighbour once who'd later fallen over on the frozen puddles left behind though.

Point 3 by HB above is also one I've used on many occasions. It's a very nice way to wake up, if not quite as satisfying since giving up the weed. ;-)

Cheers
DP
Does anyone else use warm water to defrost cars? - Another John H
No.

I used to do the warm water thing, but now my prefered method is to put a 1kW fan heater on the rear parcel shelf before I get my breakfast.

20 minutes later it's all nice and warm inside, and all the windows are clear, and I don't get the re-freeze a few minutes up the road on really cold mornings.

The only downsides are the outside mirrors still frozen, and winding the lead out and back in again.

Does anyone else use warm water to defrost cars? - Red Van Man
The water used doesn't have to be warm!

I use cold water straight from the tap, obviously the tap water must be a degree or two warmer than the windscreen.
Does anyone else use warm water to defrost cars? - Ben 10
I except the practicalities of using the water to defrost, but those of you who switch on every electrical device full bore at start up in cold weather are asking for trouble.The juice draining from a battery for central locking, fan on full, heated rear,front screens,heater, lighting. Think about it. Even the juice needed to turn the car over at the same time. You're asking for trouble. Any battery will find this a strain let alone a near dodgy one.Cold weather is good for sorting out the "men" batteries from the boys.Be less of a burdon on the poor battery.Turn over, leaves lights off. Heater fan on number 1. While doing this scrap or water the ice off. Battery gets enough juice and the heater heats gradually with the engine. All you are doing by having the fan blowing on full is using more juice and blowing cold air. Warm air won't come through until the engine heats up.For those of you with good maths heads, calculate the juice needed to operate all these gizzmos and what is in the battery at the time. Be gentle and you might get through the winter.
Does anyone else use warm water to defrost cars? - the swiss tony
I think you will find it doesnt matter what speed the fan is running to that amount of power used.....
the speed is regulated by a variable resister.

I do agree that you should stagger the use of all electrical consumers.. and start the engine before turning ANY consumers on.
Does anyone else use warm water to defrost cars? - ex-Triumph man
What nobody else seems to have picked up on is to remember to switch your wipers off BEFORE you switch off the ignition. That means that is it freezes overnight, the wiper blades will not have frozen to the glass half way across the screen. The first thing that happens when you switch on the ignition is the wipers will want to carry on, but the blade rubbers are stuck. You could end up with damaged wiper linkage or if you are lucky, a blown wiper motor fuse.
Does anyone else use warm water to defrost cars? - the swiss tony
What nobody else seems to have picked up on is to remember to switch your
wipers off BEFORE you switch off the ignition. That means that is it freezes overnight
the wiper blades will not have frozen to the glass half way across the screen.
The first thing that happens when you switch on the ignition is the wipers will
want to carry on but the blade rubbers are stuck. You could end up with
damaged wiper linkage or if you are lucky a blown wiper motor fuse.


Very true.. I was hoping no one would mention that, as it, and misfueling are the only things keeping some dealers afloat! ;-)
Does anyone else use warm water to defrost cars? - billy25
Twas so cold here last night and first thing this morning that i heard a neibough complaining that his hot water was freezing before he could get it from the tap to the car!!

Billy
Does anyone else use warm water to defrost cars? - John F
I use a storage heater. One bar element failed on an old long thin toaster so I fettled the innards to make the other stay permanently on. I put half a rosemary roof tile in the 'toast' area and wired it, via the boot lid, to a push-in two pin connection [small hole through nearby wall into workshop] which delivers the last hour of off-peak electricity [approx 3 p for the remaining 500watt element. It is strapped against the front of the driver's seat. It warms the interior of the car and the steering wheel and clears the frost from most of the windscreen. The concrete tile continues to deliver pleasant warmth to the backs of the legs for the first few miles.
It helps to remember to disconnect the wire before driving off!

Does anyone else use warm water to defrost cars? - captain chaos
I always use a scraper, de-icer if it's a really heavy frost. A chap across the road poured water on his screen and cracked it. I managed to crack a screen during the winter of '82 when it was so cold the sea actually froze at Blackpool. I cleared my screen with a scraper as normal but when I got to work noticed a crack about four inches long across the bottom of the screen. It must have been caused by the demister heat and the outside temperature (around -25 with the wind chill) :-(
Does anyone else use warm water to defrost cars? - Rudedog
I'm sure BR's will laugh at me, but my heated washer jets have never let me down when combinded with the correct strength of screenwash.
Does anyone else use warm water to defrost cars? - rtj70
Only once had heated washer jets - on a hire car in 1990. On a customer site in Litchfield and lived in Manchester. The weather was terrible during the day and work went wrong and I had to stay. Kept popping out to the car during the evening to clear it of snow and make sure washer jets working.

Much later I setout and all was working. Get on the M6 and a fair bit later everything starts freezing. Washer jets frozen and screen freezing quickly. Not a great trip home. And to top it all, get on the A5103 in Manchester and get on some black ice and start sliding towards a police car. First rear wheel drive car for me and somehow I steered in the direction of slide and all fine.

Oh for the Ford heated screen. No doubt if there was correct level of screen wash this car would be fine. The auto gear box was handy in winter mode - my normal car was a ten year old Fiesta!

Edit: And yes I do sometime use luke warm water. Worst frost I had was parked near East Midlands airport - car totally frozen. In a hotel car park. Water bottles in the boot also frozen. I had de-icer.

Edited by rtj70 on 30/11/2008 at 20:33

Does anyone else use warm water to defrost cars? - hcm
Could one of the resident policemen answer this?

If tap water or de-icer were not available and I were to stand on my bonnet and melt the ice on my windscreen using my own warm water supply would I be committing an offence?

Doing so in a public place does seem to be a no-no.

However if I covered myself in a tarpauline would I be OK?
A warning triangle 25m from the site?
Emitting a loud beeping noise mid-flow?

I would like to know before the morning if possible.

Thanks.
Does anyone else use warm water to defrost cars? - Alby Back
Are you taking the .....?

;-)
Does anyone else use warm water to defrost cars? - rtj70
This thread is starting to degenerate. A summary would be that nearly all that respond says they do indeed use warm/tepid water to defrost cars. And there is some concern that this could refreeze on the car and especially on the road.

So unless there is something new to add to this (it's not a poll) then think before replying.

Ta

Rob (as a moderator)
 

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