I overheard a couple of oldtimers talking and one bragged to the other about his grandson and how great a scout (Boy Sout I assume) he was. He said that the kid could boil water in a paper bag. I know this is physically impossible but am curious on the origin of the phrase.
Actually it’s supposed to be possible, although a paper cup is more commonly quoted. The idea is, the paper is so thin that it can’t get appreciably hotter on the “flame” side than the “water” side, and the water cannot get any hotter than 100[sup]o[/sup]C. I think it’s meant as a science demonstration rather than a practical way of making your campfire coffee, though.
If I can find a paper bag, I’ll give it a shot and get back to you!
I never tried a paper bag… I would think the water would soak through it, and the bag would rupture!
In 7th grade, though, we DID boil water in paper Dixie cups! Interesting little demo.
“My Side Of The Mountain” by Jan something.
Talks about boiling water in large leaves becasue the water boils before the leaf burns.
–Tim
I’d like to say the cup of tea I’m drinking right now was made with water boiled in a paper bag, but…
exp1) MacDonalds takeout brown paper bag - sprouted leaks everywhere when filled - experiment aborted
exp2) square pouch 3 inch x 3 inch x 2 inch deep - made from folded sheet of inkjet paper, stapled at tops of sides.
Too permeable - water seeped through it. Survived 30 seconds on gas burner before experiment aborted due to too much mess.
exp3) repeat of experiment 2, using glossy paper from cover of Computer Shopper magazine. Pouch didn’t leak, but was too weak to survive being placed on gas burner. Water everywhere.
exp4) envelope with a little water, held so all water in one corner. Dripped slowly but I could live with it. Could be held directly in gas burner flame without visible damage. However, heat rising from the burner browned the dry parts of the envelope. 2 minutes in flame left the water hot but not painful - experiment ended due to growing puddle on top of the stove.
exp5) Magazine paper pouch as in (3), but pouch is placed in frying pan. I know that’s cheating, but it’s not a bad approximation to charcoal embers. An inch of water was raised to near-boiling without trouble. As soon as boiling started, the bubbling made holes in the paper.
exp6) cardboard 6 - egg carton: five egg holders filled with water. Placed on paint tin with one water-filled egg-holder hanging over the edge. Candle placed under egg-holder for five minutes. Lots of soot on the bottom of egg-holder - very smokey! Water hot enough to make me swear. Egg holder not burnt.
Further experiments were halted by housemate enquiring why I was trying to burn the house down AGAIN.
Scouts may use a particular kind of paper bag, but I’m betting they put their fire out more often than not. If they don’t, then I bet they spill the water everywhere trying to pour it. But it’s possible, just!
The bag has to be kept out of contact with the flames. Paper burns at F451°, while water boils at around F200°. You need to suspend the paper bag far enough over the flames to keep drying out the paper yet absorbing enough heat to eventually boil the water.
Now now people, just pour the water into a paper cup and use the device known commonly as the microwave 
Once, out in the woods with friends, I filled a plastic cup with water and put it in the fire. It was at the edge of the fire, so it wasn’t TOO hot, but the water slowly evaporated and the cup only melted where it wasn’t in contact with the water, so the cup melted slowly from the top. Neato.
So, YTDread, it’s not just an expression, as several people have said, it’s quite possible. Those old timers weren’t just using some out-dated expression to confuse you.
matt!!! You’re my hero!! Now THAT’S fighting ignorance!!
You go, girl!!
Very common old Boy Scout trick, this. It is, I should mention, a remarkably easy way to hard-boil an egg. Fill the paper cup with water (incidentally, the wax will melt if you pick a cup that’s been waxed; just plain paper is preferred) and drop in an egg. Place the cup in the cooler coals near the edge of a fire and let it boil. The top of the cup will probably singe away, but the part that’s in contact with the water never gets hotter than 212F, which ain’t hot enough to burn paper. Remove, and enjoy your hard-boiled egg.
Several years ago I won $10 from my brother because he didn’t belive that I could do this. Howeve, I had trouble seeing how this would be usefull. It burned away all of the cup that was above the water level, and the cup was too hot. We Couldn’t find anyway to get the cup off of the fire without burning ourselves. I guess if you bring tongs camping with you, you could use them.
Thanx for your prompt and concise answers.
There is a ractical Boy Scout application of all this. If you know what you’re doing you can peel birch bark, form it into a large cubical kettle", and boil water in it for whatever purpose. It takes some knowledge and skill to peel the bark without putting holes in it (it helps to "beat"he tree first), but a bark container with ater in it supposedly won’t burn, whereas an empty bark kettle WILL.
I’m an ex-eagle scout, but I’ve never don this. I HAVE boiled water in a playing card with the edges turned up, using a atch as a source of flame.