# Sleep Warm Anywhere

## Step 7: Make a Hot Water Bottle

This is an excellent trick. Just before bed, fill a lexan bottle with hot water and wrap it in some clothes. This is also a twofold step: It'll warm you up initially, and you can drink it if you get thirsty in the night. Just make sure that lid's on there tight.
Many people have suggested the use of rocks instead of a water bottle, but believe it or not, water stores more heat at a given temperature than stone. The measurement of how much heat a given volume of something stores at a given temperature is called volumetric heat capacity, and water's is about twice as high as granite's. To put it simply, if you heat a liter of water and the same amount of stone to 212 degrees Fahrenheit, the water will release about twice as much heat as it cools to the ambient temperature of your bag.
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fostermoody says: 1 year ago
Actually, a good trick I have found is that you can combine steps 6 & 7. It does mean that you can't drink out of the bottle, but you do get the benefit of not losing any of your precious body heat.

Unfortunately combining the steps is a fair bit less convenient for that half of people with female urinary tract, though still doable if they're careful.
cletusjo says: 2 years ago
On the issue of water vs rock. Perhaps you are correct on a volumetric however volume is a 3d measurement. A foot cube of water will be considerably less dense/heavy that the same block of stone. So from a space perspective the rock should win. Density water ranged from 1.860 at 212 F to 1.940 at 32 F. while "granite" since you mentioned it, has a range of 2.6-2.7.
2.65 / 1.9 = 139% increase in density.
So if rocks are available and you have a fire, you should have already built a heat wall to reflect the radiant energy of the fire at yourself from the far side of the fire. Why not use those same rocks again to stay warm through the night.

You could also start a small fire, dig a trench a few inches deep and your body wide, piling the dirt all to one side... then build the fire along the length of the pit. and put in rocks.. then when it's time for bed you knock the dirt over the fire putting it out and trapping all the heat underneath. Put your sleeping back on top and roast away.
SIRJAMES09 in reply to cletusjo2 years ago
make sure you have AT LEAST 6 INCHES of dirt on top of the rocks & hot coals...otherwise, you'll be needing another sleeping bag & maybe a trip to the hospital for the burns you get from the hot coals.

But sleeping on rocks & hot coals is what I always do...works every time. :)
shawna68 says: 4 years ago
I bought the little hand warmers and put them in my backpack, they take up no room, so when I went to "bed" I just opened them and gave them a little shake to activate and stayed warm all night, since they are 10 hour warmers the nest morning it was very cold and I had them to put in my pockets.
Arano in reply to shawna682 years ago
what type of hand warmers do you mean? those NaAc ones (those plastic bags with liquid and a metalchip which turn solid and warm when the chip is bent) or a type of handwarmer that burn coal or lighter fuel?
Kementari in reply to shawna682 years ago
I've used hand warmers in my sleeping bag for cold-weather camping and they work GREAT. They make a big difference in how quickly the bag warms up.

I also bring some when traveling, even when I expect to sleep in a bed, in case the hotel or friend's house I'm staying at is too cold.
True but you can heat the rock above 212F but be careful when you do.
I;ve used this technique and it's a good one - heating several rocks by the fire and place them around you to keep warm - if you have enough rocks you can rotate them through out the night. Smooth river rocks are best - no sharp corners to poke you in the night. I've heard Potatoes are also a good one and can be used the same way. Though i've never had enough around when camping to cook and keep me warm. lol

Keep in mind the less you carry in - the lighter your pack and the less you may have to carry out.

Using what you can that nature provides or the area your in provides can work in your favor when trekking for a few days.

-chase- in reply to -chase-3 years ago

PS - Don't forget - if trekiing with someone - you can always share body heat to keep warm. Besides with the right hiking partner - this can be more fun than a sleeping bag full of hot rocks or a hot water bottle! ;0)
mreusguy in reply to -chase-3 years ago
take my wife she puts out way too much body heat!
-chase- in reply to mreusguy3 years ago
LOL!  -  are we talking hot headed or hot bod?....... if hot bodied - sure i'll take her - if both - sure i'll take her.... if neither, then all one can say is
- Hey you married her i didn't.

;0)
podup365.com says: 4 years ago
Why not combine this step with the previous one and make a hot pee bottle? For basic camping, this may seem gross. If it's a life or death survival type if incident, this could save your life. Ok, so it won't start out at 212 degrees, but you also don't have to leave the warmth of your tent to go waste heat the side of a tree. Make extra sure the lid is sealed on tight, too. As for your math with the rocks: The hot water might store more heat and release twice as much, however it does so at a faster speed than the rocks will, especially if you heat the rocks and bury them in the ground underneath where you are sleeping. Sure, digging is more work and sleeping on rocks could be uncomfortable if you don't cover them with enough earth or something softer, but once again the process could save your life. Plus, the work of digging will keep you warm while your rocks heat up by the fire and you will work up an appetite for the food.
Mother Natures Son (author) in reply to podup365.com4 years ago
Many people have suggested this, and it certainly seems like a good solution to a common problem. I've personally never tried it, and I'm not sure I'd be willing to take an empty water bottle out for the sole purpose of struggling around in my sleeping bag and trying not to wet it. I suppose it's a matter of personal preference. As for the rocks, I suppose it would help some to bury them, but I think at that point you'd be heating the ground more and yourself less--and it wouldn't work at all in snow. Plus, if you have a big enough fire to make that practical, you'd probably be better off curling up close to it than mucking about with rocks. With this type of thing, it's probably best to apply Occam's Pocket Knife.
whitepinoy in reply to Mother Natures Son4 years ago
As for the snow it really depends on how much snow is on the ground. is you only have a few inches of snow then you should remove it before setting up your tent since it will melt durring the night anyways. If it is feet of snow then yes you wouldnt want to bury rocks in it. you can just pile the snow on the side of youre tent ( a few inches) to help insulate the lower part of your tent.
blackflame002 says: 4 years ago
I've tried this a while back while camping. i used a nalgeen bottle and it was still hot when i woke up.