Non Linear Halfords Concentrated Screen Wash

[Vortex13]

Used undiluted it claims protection to -20C

50% dilution claims protection to -7.5C

How does that work then?

[Caecilius]

It's probably a mixture of alcohol and water. The alcohol is probably methanol, as that's the cheapest alcohol available.

A google for "methanol water mixture freezing point" shows that the freezing point vs concentration graph is non-linear.

[Max Demian]

I would have thought that methylated spirit is cheaper (ethanol with around 7.5% methanol). (I used to add meths to my washer bottle, which coloured the plastic purple.)

So is ethanol.

[ARW]

The thing is it does not work!. Get a minus 4 night and at 50% dilution it will have frozen.

[Muddymike]

So true. That's why I add meth to mine.

Mike

[Caecilius]

I think methanol is the cheapest at the industrial level, but I might be wrong.

I wouldn't use meths myself, as I don't like the pyridine smell, and I suspect that it would rot the windscreen wiper blades.

[Brian Gaff]

Brine. Brian

[Brian Gaff]

If you look at mars, There has been running water on the planet recently even though the temp is low and the air pressure low and one would expect it either to evaporate or freeze, its only because its salty or mixed with minerals that it is still fluid long enough to flow.

Water is quite interesting at the molecular level, expanding when cold and when hot, it can also pack itself in ways that allow gasses to exist between the molecules without being absorbed. Brian

[ARW]

But it's not just screen wash is it?

De-icer these days only seems to work when it's above minus 1 deg regardless of what it says on the tin.

[Bob Minchin]

+1

It has always stuck in my mind what I was taught at school in the 60s which was without the weak hydrogen bonding of water into a molecule (I think with 18.H2O), water would be a gas at room temperature and we would not exist being mainly composed of water.

Bob

[Andy Burns]

Get the VW stuff (rectangular bottle part number G052164M1 they do another round bottle, not as good).

Claims -70°C at 100% and -16°C at 33%, I probably use 10% and never had it freeze, was -8°C the other week, also it's not the gloopy PEG type.

[The Natural Philosopher]

Isopropyl I would think. But could be ethanol/methanol

[The Natural Philosopher]

windchill makes the alcohol screenwash useless at speed. I remember driving up N German Autobahn at subzero withh freezing fog icing up the aerial, and the screenwash simply stopped working till the Defeneder stopped moving. Then it froze as soon as I started again.

I generally use it neat as well

[Andy Bennet]

How does what work?

Are you expecting 50% dilution to be -10C? Why?

Is 20C twice as hot as 10C? Is 40C twice as hot as 20C? Of course not.

You should use the Kelvin scale for comparisons, 253K for -20C and

265.5K for -7.5C to get a true comparision of concentration required v temperature.

Andy

[GB]

I hope it doesn't forget to do that. I wouldn't want to explode suddenly.

[Bob Minchin]

Yes that is sort of the point. A so-called 'weak force' is utterly critical to our whole civilisation. Beats Trump LOL

[newshound]

That's only in the purple "domestic" stuff, proper "Industrial Meths" doesn't have it.

[DJC]

During the recent cold spell I spayed de-icer on the windscreen, which promptly froze making things worse. I wasn't below -2C.

[Bob Eager]

I've used it for about 40 years, and I've never had problems. I quite like the smell...

[dennis]

That isn't surprising. You melt the ice and that takes heat to do so. That mostly comes from the glass so it gets colder and any remaining water/fluid will freeze. If there is a lot of ice it will get so cold the insides will condense and freeze.

Its simple physics and its the reason I don't have any de-icer but I do have a scraper.