Not really a question, but when camping recently, the SO and I were about to melt snow for water when she says "Put a drop of water in the bottom otherwise the snow burns".

WT?!?! Apparently she was told this on an expedition in Greenland – when the snow is so cold apprently it burns before it melts because it is too dry. Plus she reckons they could smell burning if they didn't put a small amount of water in the bottom first.

I know water will help conduct the heat better from pan to ice but burning snow? Never heard anything like it…!

Could it be residue on the pan that burns rather than the ice?

Utter tripe I'm IMO. You can sublime the snow (i.e. turn it directly to gas without the water stage, which would be a waste and may happen in this case) but it can't burn, it doesn't oxidise. What they're suggesting is adding the water to gently heat the ice so that it doesnt get chance to "sublime away" before getting turned into tea. There should be bugger all impurities in good snow (non-yellow etc). It could be that you were using a teflon coated pan and THAT burns off when overheated without fluid in it.

it may just vaporise it too quickly.

the burning smell could be impurities left behind?

😯

CK – exactly, thank you.

burns into what ?

Burning in air is adding oxygen to it, and the only molecule I know that you can get by adding oxygen to water is hydrogen peroxide, however, that reaction is endothermic – ie you have to add energy to make it happen, and I think it would require high pressures and/or catalysts

No of course not – but the pan might, just as if you put it on the heat with nothing in it.

I should be extremely surprised if you managed to sublime snow/ice. You'd need to be at extremely high altitude to manage that, at which point lack of water would be the least of your worries. From a practical point of view though, due to the difference in heat conduction between snow and water you could boil off any liquid water as fast as you melt it.

Plus she reckons they could smell burning if they didn't put a small amount of water in the bottom first.

Probably stuff on the pan burning rather than water. Having water in the pan probably help to protect it by preventing it getting above 100C.

I should be extremely surprised if you managed to sublime snow/ice. You'd need to be at extremely high altitude to manage that, at which point lack of water would be the least of your worries.

No you don't, that's why icecubes shrink over time and food gets dried out if left in the freezer for ages. I think…

Probably stuff on the pan burning rather than water. Having water in the pan probably help to protect it by preventing it getting above 100C.

Yep. I can't imagine snow is a great conductor of heat and snow requires energy to change state to water so it will take a while before it starts taking heat away from the pan efficiently.

Can't burn. Water is a by-product of combustion, innit?

You're kind of right – my mistake, CK. You can sublime ice given sufficiently dry air, hence low partial pressure of water vapour (I was thinking it required that low atmospheric pressure). I still think you're unlikely to get those conditions inside your pan apart from for a very short period – the water vapour you initially generate will increase the partial pressure and prevent further sublimation.

I think the expedition leader spotted a gullible member of the troop and went for it. 3 years later and she was having one of those incredulous "Its true, you wait til we get back and I'll prove it!" moments. Ok, dear…

In my experience it's the pan and any residue left in it that makes the melted snow taste burned (burned rubber actually!) if you don't use a little melted water to start things off … oh and add a little snow at a time and letthat melt rather than just filling a pan with snow and cranking the heat up

Next time you tell people your Wife is special at least you'll mean it.

So adding water to the bottom of the pan will aid the melting and prevent the pan from 'overheating' and flavouring the water.

only in a titanium pan

It's true you can give wated melted from snow a 'burnt' taste. I speak from experience, also in Greenland and other places. It seems a bit like scorching the snow, it goes from cold to very hot too quickly.

The sublimation of ice into vapour is how they freeze-dry food.

It seems a bit like scorching the snow

but it isn't 🙂

I always thought you should add water when melting snow in a pan as it makes the snow melt quicker, using less fuel. Which is important on expeditions. Not sure on the physics but I'm sure snow can't be burnt!

I reckon my girlfriend could burn it…

It's true you can give wated melted from snow a 'burnt' taste. I speak from experience, also in Greenland and other places. It seems a bit like scorching the snow, it goes from cold to very hot too quickly.

Give over, it's only because you're dumb enough to burn the pan surface and then dissolve the residue. Put it this way, I spent last weekend "burning" snow for food, none of it tasted like it was burned. Nor was any of it, because you cant burn H2O. It's chemically impossible.

There should be bugger all impurities in good snow (non-yellow etc).

😕 I'm unconvinced. Well at least it depends on the definition of "good snow" I guess. I can't imagine that there's much snow which falls on the British Isles which free of impurities – however white it might be. As long as it falls through anything other than pure air, I can't see how it won't pick up impurities on the way down. I once made the mistake of collecting vast amounts of very pure white virgin snow, in the mistaken belief that once melted, it could be used in my amazonian tropical fishtank 😐

I spent the weekend boiling snow, the only impurities I could see or taste were where I collected it too close to trees that had shed some barky bits between snowfalls. Of course there may be some level of impurity but not to the extent that you'll be able to BURN it. Impurities may be acids and carbon particles, but both in such TINY quantities that you'd never notice. The melted snow I collected was pretty much tasteless, bar the slight hint of aluminium always present in a freshly scraped trangia pot.

Fried icecream, anyone? 😆

To answer the OP – my missus could burn ice!

I spent the weekend boiling snow, the only impurities I could see or taste were where I collected it too close to trees that had shed some barky bits between snowfalls.

But it would be interesting to see what it contained other than what you could see or taste, ie, a full analysis. Just for the record, I don't believe for a moment that any impurities would enough to "burn".

And I don't understand the OP's suggestion – surely the snow would melt slowly as the pan warmed up, so there would be "a drop of water in the bottom" very quickly ? The pan can't get hot, whilst the snow remains cold.

Agreed, and agreed.

There has to be at least one impurity per snowflake in order to get nucleation and snow formation IIRC 🙂

Indeed – I had forgotten about that 8)
I saw a programme last year about snow, how it was formed, etc – and very interesting it was too