Using hot water bottles as ‘cached heat’

There is no comparison using hand warmers vs a quart of boiling water. The hot water bottle will help drive out moisture from
your sleeping bag and clothes too, hence you will be warmer in the long run and your insulation will be more efficient.

Try them and see.

I don't know, David. Grabber Mycoal's body warmers put out an impressive amount of heat for nearly 12 hours. Not bad for 1.2 oz. each.

On really cold trips I also bring 1 pint bottles and use them in the
morning in my double boots to prewarm them and then tuck the still warm bottles in my parka pockets or the small of my back
till camp is broken down.

I'll have to give that idea a try! Putting feet into cold footwear is one of my least favorite things. They eventually warm up but takes forever when very cold. Bonus … it leaves you with a liter "not yet cold" water to drink while you are moving.

You can get the reusable sodium acetate phase change hand warmers, and they are pretty reliable. They are not terribly hot, though. Being recharged in boiling water makes them good.

–B.G.–

On a recent trip, a guy I was with used a stainless steel water bottle and put a wool sock over it. He said it lasted all night.
There must be something to stainless.

Nah, it's fairly conductive, though not near as bad as aluminum. Most thicker type plastics used for water bottles are significantly less conductive than stainless steel.

A simple way to test this, is to fill up a stainless steel bottle with boiling water, feel it after a little while and do the same with a thicker plastic water bottle.

The stainless steel bottle will feel much hotter to the touch than most of the thicker plastic ones, and that's because it's conducting the heat out more efficiently.

If the wool sock helps the stainless, it will definitely help a thicker plastic bottle.

It seems like the bottle would mostly cool down by morning

My body gets gradually cooler by morning – my metabolism slows down, the outside temperature gets gradually colder

The problem is that if I get cold, can't sleep, so I just get up

It's better when I have sufficient warmth so I stay in bed until the sun comes out and starts warming up

It seems like the hot water bottle doesn't help much for this situation, so it's not a very useful technique

If someone, like, had hypothermia and needed to warm up it would be good

Jerry-

Keep your stove handy just out from under the tarp. After the first bottle goes cold (usually 6 hours for a quart in a wool sock in my bag) I pour it back in the pan and boil it again, all from the comfort of my sleeping bag. Then there is enough heat for more sleep and you can keep it inside your parka upon arising and breaking camp. Feels good on stiff back muscles. Recently I have been using the Gatoraid bottles for this. I replace the bottle each trip.

It helps if you use a wood stove so you aren't using a ton of fuel on hot water bottles.

My main hiking buddy uses a 3 liter nalgene bladder. He will sit there heating up the water by the fire and filling it. It's incredibly warm.
In the middle of the night he will wake up, restart the fire, and refill the bag with hot water.

btw, Justin you are like the new bob gross.

i'm not too concerned about the bottle cooling by morning. my thinking is to the extent that i'm not wasting personal calories to warm me and my sleeping bag because i'm using hot water bottles is a big plus. the hot water bottles warm my sleeping bag faster than i could and give me a reserve of calories to burn later in the night. one of the problems of cold weather camping is eating enough calories to begin with so if i can save some that's great. i'm also a fan of eating something(three musketeers/snickers) and brewing up a hot beverage right before i go to sleep for some extra fuel for the furnace. as an additional plus, the water that's cooled overnight gives me a head start on the water i will need the next day.

Maybe in 30 more years and with A LOT more experience I will be Bob Gross? Also i probably got a much stronger "mystical"/spiritual side, well who knows. Maybe future Bob learned how to time travel and took one of his past young selves from an earlier time (me) and injected them into a latter time frame…? Hopefully it won't create any irreversible damage to the fabric of time-space. That would kind of suck. Bob, we should know better!

"not wasting personal calories to warm me and my sleeping bag…"

A lot of people are happy with this so I just let it go, but

when you go to bed, your metabolism is higher so you quickly warm up your sleeping bag

the problem is at the end of the night when your metabolism has slowed down

I suppose if you went to bed really cold, it would tap into your reserves to warm up so you'de have less at the end of the night. Or if you were treating someone with hypothermia, then definitely warm bottles would be good.

But in normal conditions, if your sleeping system isn't quite warm enough for conditions, warm bottle won't make much difference

I normally go to bed a bit warm and leave sleeping bag open a bit and close up when I start to get cold. If I had a warm bottle, I'de just delay closing up a little.

we are talking about different situations. if i'm planning on using hot water bottles it’s because my sleeping bag is cold when i get in and i plan on zipping it up tight, pulling the neck closed and reducing the size of the face opening to the point that all you see is my mouth and nose. i'm not letting any hard earned heat escape once i get in and with any luck, i'm not getting out until it is time to get up. i find that i can fall asleep much faster if i’m warm, and i can get the inside of my sleeping bag warmer faster with the use of hot water bottles. once i’m asleep i can stay asleep even if i cool off some by the morning. a hot water bottle at your feet and one between your thighs is just a glorious way to fall asleep especially when it’s single digits f or below. if i have the luxury of lounging with my sleeping bag open because i’m too warm before i go to sleep i’m not using hot water bottles either.