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chogori


Mar 22, 2005, 12:47 AM
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Melting Snow
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Okay, so the holy bible of mountaineering (Mountaineering Freedom of the Hills) says very little on this, and Mark Twight is talking about some stove modifications that I'm sure will only end in something getting blown up, so I just got to ask... what is the best way to melt snow?
This may seem like a simple question, but there's a lot of factors. For instance, should I, as soon as some of the snow begins to melt, stuff more snow in? Or would it be better to let the present snow fully melt? Or should it be brought to a boil? Should I save some water that I was sleeping with and boil that and add snow to it? Anyone have any tips or tricks?
I've only tried the stuffing snow as soon as it begins to melt technique on a Jet Boil at 13,000 feet, and I tell you what, it took HOURS before I had 4 Nalgene's worth of water. So yeah, any thoughts?


scottquig


Mar 22, 2005, 12:56 AM
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I haven't heard of any tests to see what works best, but I was taught to mix the snow with water you've already got melted right from the get go. Then, as the snow melts, add more. I don't think it should really matter in any case--the amount of energy required to melt x amount of snow is the same. Any energy put into the snow will go to melting the snow and not to heating it up. That is, until all the snow is melted. Sorry if that doesn't make sense. It has to do with latent heat as opposed to sensible heat.


gunkiemike


Mar 22, 2005, 3:13 AM
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Unfortunately, there is more to it than just latent heat. If you keep the water very hot, the transfer of heat to the pot is poorer (wasting fuel) and there is energy lost as vapor (a gram of water evaporated = 6.7 g of snow melted, energy-wise). So do not let the liquid heat up until you need it hot.

There are a couple things to watch out for. If you add too much snow, what little liquid you have will be absorbed upwards into the snow, which can easily leave a dry spot in the pan. This could cause the pan to overheat. Also, when the pan is cold, there is a lot of condensation on the outside (which actualy is a good thing, energy-wise). On some feeble stoves like my old Optimus 8R, this can drip down onto the burner heavily enough to put the flame out.

If fuel is running low (and you have the time), melt snow over a low flame. A huge flame typically is less efficient and loses a greater fraction of the heat up around the outside of the pot. The exception would be in extreme cold where you're losing heat as fast as you put it in.

Finally, yes, it is a good idea to start the process with what little liquid water you have on hand.


chogori


Mar 22, 2005, 9:36 AM
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Alright... so that's interesting. Based on gunkiemike's response, it sounds like the best formula for boiling multiple liters of water is to:
(Starting well before you want to leave, obviously)
Pour x cups of water from your current stash into the stove pan.
Fill with snow.
Cook on a low flame.
When all the snow turns to water refill with snow.
Repeat above step until you have a full pan, then repeat the whole process in a new pan.
Hmm, okay, questions:
How much water should the x cups be? Should it be half a liter, or 1/4 or just a cup?
And I'm still unclear as to when to add more snow. I see what you're saying about the dry spots contraindicating the stuffing of more snow as soon as there's room, so does that imply that I should wait for it to pretty much completely liquify before adding more, or add more when it's half melted or what?
And should the snow be densely packed? Or just sluffed in?
Thanks.


montafoner


Mar 22, 2005, 10:08 AM
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When adding snow to the water, I would not pack it together. Loose snow has a much larger surface area and will be able to absorb energy (heat) faster.

For the opposite reason, an igloo or snow cave can get quite warm as the inner surface will melt and re-freeze, reducing the surface area and slowing the heat loss process.


jackscoldsweat


Mar 22, 2005, 10:41 AM
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don't forget to stir.....

JCS


jimdavis


Mar 22, 2005, 2:46 PM
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Start with water in the pan, and use Ice over snow if you can, it'll save a lot of fuel and time. Otherwise your gonna be shoving snow in that pot for a long time.

Cheers,
Jim


tallnik


Mar 23, 2005, 8:00 AM
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Couple of mods that will not kill you, but will make boiling water faster. If I mess up the "science" behind any of these mods, I'm sure someone will point it out.

1) heat exchanger for your pot. Something they should have at your local gear shop. essentially a metal device which goes around the pot, tries to "re-cycle" the heat lost by the pot back to it.

2) Depending on what type of stove you use, a metal wrap can be place around the stove to trap any heat that would be lost between it and the pot. Works as a windshield as well. Have only encountered this with MSR whisperlite style stoves, but can see useful applications to others as well. We used what looks like uber heavy duty aluminium foil.

Hope that's clear enough.
Nik


iceisnice


Mar 23, 2005, 8:12 AM
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if you are melting it just for drinking (not for a meal) don't bother boiling it. just melt it. there are very few organisms that can survive in the snow. boiling is just wasting fuel....if that is a concern for ya. most backcountry books scare ya about giardia and all, but i hardly ever use a filter or boil my drinks and have never gotten it. you just have to pay more attention to WHERE you get you water/snow from. not sure if you already know this. i always try and go as light as possible and fuel is one thing i've always had a hard time figuring out the minimum necessary for trips.


thedesertnomad


Mar 23, 2005, 9:39 AM
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I have always found the best way is to cook on med to low flame and spend the time to put in fluffy powder a spoonful at a time and stir stir stir, I also put off so much heat when hiking I usually fill a nalgene or dromedary bag with snow and put it on my chest for the hike, it gets the process started and keeps me quite cool. It is a long drawn out prcoess.


adamtd


Mar 23, 2005, 10:41 AM
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I would venture to say that this topic has gotten to scientific. in teh 10 years I've bene melting snow/ice for water, the best stove I've found is my MSR whisperlite, full bore open, creating as much heat as possible. I put water in the pot, not so much to help withy melting, but to keep from burning the snow (don't believe me, try it, it tastes aweful). I add as much snow/ice to teh water as I can so that it doesn't soak up all the water in teh pan (allowing me to burn my snow). Ice works better than snow, simply for teh expansion ratio, 10 cups of snow equals 1 cup water. I don't know what the expansion range is for ice, but it's a hel of a lot better than 10/1. If you're only using it for drinking, don't boil it because it's a waste of fuel, but if you're out in the snow and ice, what are you doing skimping on fuel?! Experiment with it, and find your bets style, just as it is with everything else... don't worry if someone tcriticizes the way you melt snow for water... tell them they have too much time on their hands.


helmut


Mar 23, 2005, 10:50 AM
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Does anyone have any good recipies for peanut butter and jelly sandwiches?


reno


Mar 23, 2005, 1:58 PM
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In reply to:
if you are melting it just for drinking (not for a meal) don't bother boiling it. just melt it. there are very few organisms that can survive in the snow.

You mean other than Salmonella Typhii, poilovirus, and Hepatitis A, right? ;)

Boil your water.

To the Original Post, I've had more success when I packed the melting pot full (press the snow in firmly... loose snow = air gaps. Air gaps = scorching,) and then added some water... usually 100mL or so.

FYI, I use a Wisperlite International, and white gas fuel. And the windscreen. Been meaning to get one of the heat exchangers (available at REI,) but haven't yet.... budget issues, you see.


jackscoldsweat


Mar 23, 2005, 2:04 PM
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so...reno..

on a remote alpine climb with little fuel to spare would you still boil ?

just asking...


JCS


greenketch


Mar 23, 2005, 2:22 PM
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Definatley keep plenty of water in your pot and add snow as you can. One other tip that works well on all except the cold trips. Take along a large black trash bag. When your messing about or on summit day put a bunch of snow in it and leave it for the sun to get. I usually have at least a couple liters of fresh water when I get back.


reno


Mar 23, 2005, 2:26 PM
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In reply to:
so...reno..

on a remote alpine climb with little fuel to spare would you still boil ?

Probably, yes. I might not, if I had the option of collecting freshly fallen snow, or if I was on my way out and knew I could get medical care soon, but overwhelmingly, "Yes, I'd boil."


sandbag


Mar 23, 2005, 2:28 PM
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boiling snow is overkill if youre on a peak, and esp if its not grimey dirty snow. That being said, there is a snow fungus, Gyromitra genus that looks like purple haze. Dont use snow from these areas(usually spring) and or below because youll not be happy with the results:

In the stomach, gyromitrin is rapidly hydrolyzed into acetaldehyde and N-methyl-N-formylhydrazine (MFH), which then is slowly converted to N-methylhydrazine (MH). Both MFH and MH are toxic to humans. MFH inhibits a number of hepatic systems, including the cytochrome P-450 and glutathione, and causes hepatic necrosis. MH inhibits pyridoxine kinase and interferes with all the pyridoxine-requiring enzymes in the body, including those involved in the synthesis of GABA. The reduction of GABA in the brain leads to CNS hyperexcitability and convulsions.

but melting snow will also have a lot to do with the outside temps too. trying to melt in a metal container is a funny energy wasting event at best but better than nothing.


chogori


Mar 23, 2005, 6:18 PM
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Alright, awesome, so lot's of good information here. Thanks guys.

On the subject of boiling - I was told that it is generally a huge waste of fuel trying to boil your snow-water at altitude. And from what I've seen, I'd have to agree with this. Trying to get snow-water to boil at 15,000 feet is a joke. It just doesn't want to happen. I mean, I've melted water on quite a few occasions and didn't boil it, and I haven't fallen ill or anything, but does anyone know what the big time mountaineers do?

And on the subject of packing snow into the pot- It seems like you folks have conflicting opinions on snow packing... so what is it? To pack or not to pack? Does anyone have any numbers or know for sure?

The trashbad is a good idea. I like that one. As for the folks who carry ice in their jacket... it actually melts? The last climb I did the water in our jackets actually froze over the course of the day. Granted it was insanely cold, but still, I feel like ice probably wouldn't melt.


jackscoldsweat


Mar 24, 2005, 7:53 AM
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bust out the XGK. it'll melt anything. including you and the tent if you are not careful. I've melted a good share of ice well above 16,000 using this stove.

JCS


reno


Mar 24, 2005, 9:09 AM
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In reply to:
bust out the XGK. it'll melt anything.

I've heard this too from friends that have the XGK.

Never had the chance to use it myself.... yet?


chogori


Mar 24, 2005, 9:28 AM
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Yeah, I've heard good things about the XGK. It's definitely on my (quite long) list of things to buy in the near future. But so is a new rope, and that gets top priority.
Anywho, yeah, the Jetboil sucks at altitude. Don't even think about using it. I think it might have to do with the pre-compressed isobutane canisters. I wonder if there's a pressure problem or something that causes the stove to not get enough fuel. Anybody know?


greenketch


Mar 24, 2005, 10:01 AM
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Something about the jet boil that has already been pointed out. It is not a good choice for melting snow. Not a big enough pot. Even in compact corn there is not a lot of water per unit volume. In a little cup you will get a tiny bit of water. You may be able to help by using some kind of insulator under the stove to jack up the temp of your gas a bit. But it will be hard to win. Use a bigger stove and bigger pot.

Other than that don't loose heart. The higher you go the less any of them work. Even with an XGK it takes a while. Most vetrans of big peaks will confirm that it seems like you spend an inordinate amount of time just melting snow. It's a function of stove inefficiency and low water volume. But it was you who chose to be there afterall.


jackscoldsweat


Mar 24, 2005, 11:41 AM
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i can see using a cartridge stove for anything in the lower 48 during mild conditions. but as soon as the temp and/or the altitude go extreme, leave the cartridge at home and instead bring the white gas stove. yea..you'll have to tinker with it more and be more careful, but the amount of BTU's put out vs. a cartridge means less time melting snow. and more time sleeping/suffering/freezing/FUN......

"if the route matters..i use white gas" ~twight

JCS


clymber


Mar 30, 2005, 11:09 AM
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depends on how much water you need and how quickly uou need it....another way that no one has mentioned and uses no heat is to pack in a black garbage bag with you...before you leave camp in the morn put snow in the bag and place it on your sleeping pad outside in the sun..by the time you get back to camp you have water...you are saving a ton of fuel that way and not wasting time waiting for it to melt... granted if you are in whiteout conditions it wont work...


jackscoldsweat


Mar 30, 2005, 12:05 PM
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In reply to:
... granted if you are in whiteout conditions it wont work...

or climbing over your route carrying everything with you....or alpine style....

but a very good way to save fuel none the less..


JCS

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