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marky
climber
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Topic Author's Original Post - Dec 3, 2005 - 05:03pm PT
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an alpine virgin wants to know how to do this well. Would a 2-liter pot be good for this? Maybe reserve 8 to 10 oz. of water to get the thing going, lest one produced burnt snow?
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marky
climber
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Topic Author's Reply - Dec 3, 2005 - 05:25pm PT
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let me clarify. If I just throw snow into a pot and light the stove, rather than getting water, I'll just scorch the bottom of the pot and get burnt snow. Am I wrong? I presume I need to "sautee" the pot with a bit of liquid water.
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Ed Hartouni
Trad climber
Livermore, CA
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Rajmit, have you ever boiled snow to make water? next time you've got the white stuff outside the infinite hall put some in a pot and crank the heat way up... report back here on what happens.
marky, usually I put a bit of water in the pot along with the snow to keep the temp no more than the boiling point (at what ever altitude). One fills the pot, and then keeps putting snow in as the contents melt into water.
I don't have any different size pots then I usually carry for cooking. Takes a bit of time, so logistics is an issue. Melting snow at night for water to be used the next day is my usual mode... put the water bottles in your tent, and if really cold, in your sleeping bag (tight tops!) to keep them from freezing. Melting snow in the morning takes a long time... the other thing to think about is the amount of fuel required to melt the snow, which is considerable.
edit: Kath got there first! she's right (of course)... but Raj still has a homework problem
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marky
climber
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Topic Author's Reply - Dec 3, 2005 - 05:55pm PT
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can somebody quantify about how much water I would need to reserve for a two-liter pot, assuming infinite gas and infinite snow availability? would 8 ounces cut it?
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Tuan DeLusion
Social climber
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Marky, don't listen to the teenager. The impurities in the snow will make your water taste bad if you scorch it. Little bit of water, low heat and you won't lose too much to evaporation as it takes a lot of snow to make water.
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Chaz
Trad climber
So. Cal.
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Rajmit: "say the heat source is 200 degrees farenhiet".
I don't know what cheap-jack stove you're using to make your
calculation of heat source temprature. I just fired up my MSR
Pocket-Rocket (not exactly a good first choice for either cold
weather or high altitude work) with an oven thermometer on top of it. In about thirty seconds the thermometer read about 600
degrees. I don't know about you, but if I ever find myself making
water out of snow, I'm going to listen to the guys who have been there and done that rather than risk damaging my nice titanium
cook pot by trying out a theory that looks good on paper.
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Loom
climber
167 stinking feet above sea level : (
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Rajmit says after Ed's post, Have any of you taken physics?
Have any 19-year-old idiots hereabouts ever melted snow?
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TGT
Social climber
So Cal
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Have any 19-year-old idiots hereabouts ever melted snow?
You beat me to it!
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cactus
Trad climber
okanagan
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Raj is a moron. Not just because he is wrong but because he thinks his very limited experience carries more weight than those of us with years more experience. Raj: your theoretical posings ignore heat transfer rates. If the snow can't absorb the heat as fast as the stove produces it, you get a melted pot. Oh by the way, I've got T shirts older than you!
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T Moses
Trad climber
Paso Robles
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Rajmit:
Knowledge and experience equal wisdom.
I think you don't have the wisdom to quit while you only have one foot in you big mouth.
Burning snow is a figure of speech.
Melting points of metals:
Aluminum 1217 F
Mild Steel 2462 to 2786 F
Titanium 3263 F
Have you ever heated the very middle of a sheet of metal and watch it warp and not return to its previous shape? Same thing happens to your pot.
Politely telling you to quit while you are way behind.
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Ed Hartouni
Trad climber
Livermore, CA
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Raj, enough of Greek physics, get out of the ivory tower and actually do the experiment...
I didn't know I needed a CV for you at SuperTopo, but I got a degree in Physics at UCB ('76) and a PhD from Columbia U ('84), though I specialized in Particle Physics. I may be a bit thin on Thermo though, the only lower divison course I had on it was in the class by Kittel, who mostly taught us Stat Mech, one day on thermo... after that it was all Stat. Mech.
...Raj: "I could be wrong. Though I am pretty sure the pot will not scorch/burn/melt." go out and do it dude... then report back!
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Ed Hartouni
Trad climber
Livermore, CA
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you've got to use snow...
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Terry
climber
Spokane
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Raj,
You are embarassing yourself, quit.
Hopefully you'll learn a very valuable lesson here - what you learn in books and school does not always work in the real world. Your lack of humility is gonna cost you in life or turn you into one of those management idiots who demand something impossible because it works on paper. Save yourself.
By the way I believe Ed Hartouni has a PhD in physics.
Edit: Ed beat me to his credentials.
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Tuan DeLusion
Social climber
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The only snow he knows is some lame snowjob troll. I would think a teenager at MIT would know the difference in snow and ice.
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Tuan DeLusion
Social climber
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Rajmit, you've been eating too much yellow snow.
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Tuan DeLusion
Social climber
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Tu m'emmerdes, putain!
Leave your mother out of your trolls.
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bobinc
Trad climber
Portland, Or
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Rajmit must be trollin'. Or ignorant.
I've burnt a hole right through a pot with a campstove; turns out 2 pots were nested and I didn't notice.
New "powder" snow is 90% air. Cascade cement from up here might be 40% air. The only time we get near 100% non-air is after an avalanche.
Why doncha get out and do some melting in the real world, burn some pots, climb something, etc?
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Ed Hartouni
Trad climber
Livermore, CA
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ok Raj, you need to use snow...
why? well here is a simple hypothesis... snow is a great insulator, you put a bunch of snow into the pot and really crank up the heat, the bottom layer of the snow melts and leaves a cavity between the upper layer and the bottom of the pot. My ancient cook wear is stainless steel, which has a very low thermal conductivity. In the cold of the alpine evening (or morning) the pot is only hot at the flame contact.
Still with me? ok, so the flame is sitting there heating the pot, and any of the steam which is left from the vaporized snow, the snow in the pot not in contact with the bottom is doing a great job insulating, and the pot bottom gets really really hot. Not good, don't try this with your Mom's pots, she'll kill you. The radiative heating of the snow isn't so great (snow's got a wonderful albedo) and the steam can diffuse quickly through the snow.
But it is only a hypothesis... putting water in the pot first prevents the temperature from getting above the boiling point, and provides a much better way of transfering the heat (conduction).
This wouldn't work with ice. Even if you chip it in the blender.
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Ed Hartouni
Trad climber
Livermore, CA
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People who spend a lot of time with snow know it is a very interesting material...
The Grandfield's are big advocates of snow block construction for going out in the winter, much better insulation than most tents, keep you snug when everyone else is dying (literally)... keeps the wind off, stout constuction.
Ice fields and glaciers are very interesting, complicated physical systems... Raj you would be amazed how much more subtle these things are then you could appreciate from you physics classes right now.
marky, best to listen to the experienced voices on this and not worry your pretty little head to much about the physics... Kath has it right, and bobinc got the story on what could happen, and believe me, it sucks being in the way back with one pot burnt through the bottom! up the creek without a paddle if you do it just right.
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TradIsGood
Trad climber
Gunks end of country
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Raj, just to help out a bit. You have heard people describe well their experience. You should think about whether their experience constitutes evidence refuting your theory. On the other hand, in fairness, you have not gotten a reasonable physical explanation to this point.
Snow density varies dramatically. Consider why the density is so much smaller than water. The snow is not "dry". It is ice, but the physical structure of that ice varies. The less dense (more powdery) the snow, the higher the air content of a mass of it. Air is an excellent insulator, unlike water. Alpine snow tends to occur at lower temperatures and therefore tends to have a higher air content. It also does not pack very easily. Of course, the denser you can pack it the quicker the snow will melt.
Raj, your intuition is accurate with respect to water, and solid ice. Pure ice with very little air, though slightly less dense than water, will transfer heat effectively from the bottom of a pot, if it matches the surface, e.g. if it froze in the pot.
Air is such a good insulator that I once happened on a fairly large pocket of snow when the temperature outside was 80F (very late spring). I noticed it because I walked into significantly cooler air. There was a shaded pocket of ground, that served to prevent solar heating, and also reduce convection.
So the only question, that I will leave for you here is why starting with water is a more efficient way to melt snow?
Edited: Some have added some useful information since I started this.
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