Kind of a wacky idea, but I was curious...

We know that heat will help dry out our gear, so is it possible that a Hothands could dry out a sleeping bag? Here's the scenario:

You wake up in your shelter on a winter morning and start packing up. Your down bag/quilt is slightly damp from normal nightime moisture buildup. As you stuff your bag into its stuff sack, you activate and insert a Hothands into the middle of your stuff sack, and finish stuffing your bag around it (something akin to the hot center core of the earth) You pack up and are on your way.

Provided you are not using a waterproof stuff sack, is there any chance that the hothands could dry the bag throughout the day? Is there a danger of the hothands being too hot for the sleeping bag materials? Or is this just simply a dumb idea that wont work.

Thanks, and I hope everyone had a safe and happy holiday!

Do the hot hands need air to work Travis?

hmmmm, good question

I know that need oxygen to start the reaction, but I'm not sure how much they'd need to stay reactive. That's one of those things that I'm not sure about.

People have used them in shoes to keep feet warm so I can't imagine that there is much more air there either.

They'll work inside a sleeping bag through the night for sure. You haven't lived until you have bivied out in -25°F weather (with 40+ mph winds) in a 0°F bag, high in the Colorado mountains, hugging a new hand warmer every couple hours, all night after a Grateful Dead concert. Now that's livin'.

As far as drying out a bag, I have no doubt they would speed up the process, they get pretty warm, some manufacturers more than others.

I would crack one and put it in my bag while making breakfast and packing up in the morning. I wouldn't put the bag and warmer into the stuff sack, it would be too dense to move the moisture through.

Edited by rOg_w on 12/28/2012 08:43:22 MST.

>it would be too dense to move the moisture through.

That's the big issue. Is there any empirical evidence to support this?

Hey Travis, sorry you couldn't make it to the GGGG. The water vapor has to have somewhere to go. That's why dryers have vents. While the Hot Hands might get warm enough to "preheat" the material, they get nowhere near hot enough to make any kind of a noticeable difference inside a stuff sack. I think you would probably get mold and mildew before you got dry.

Doug

Edited by sparky52804 on 12/28/2012 09:45:31 MST.

I have no experience with the Hothands brand, but I've used the Grabber Mycoal brand for years. The following is a list of the average temperature that each type of warmer will provide (the maximum could be 10-20* higher):

Hand warmer (7 hour version)--135* F
Mega warmers (12 hours)--135* F
Body warmer--127* F
Toe warmer--100* F
Foot warmer--95* F

Presumedly (and I think that I read this somewhere), the formulation is different for the various types. For example, those used with the feet have much lower air circulation, and you also don't need mega heat there. For temps near 0* F, I routinely pop a body or Mega warmer into its fleece cover and place it at the foot of my bag. They yield good warmth for up to 12 hours. I would think that this would dry out the foot of the bag pretty quickly while you have your morning coffee outside of your bag.

Please report back and let us know how well it worked if you do try it.

My guess is that it will either not dry the bag at all or only have a minimal effect, but I am only guessing.

So are you going to do a back yard test tonight, Travis? Appleton, WI will have a low of +9* F, 91% humidity, with a 90% cance of snow. Seems like the perfect time to test your Hothands. Report back, dude.

but I suspect it wouldn't work because there wouldn't be enough heat to drive the moisture out of all that insulation. Plus, if it's normal night-time moisture buildup there's really no need.

But, as has been suggested, there's a good way to find out if it works!

Ah, thanks for the replies guys. Gary, unfortunately tonight is not my night. We were planning a 3 nighter in the Porcupine Mountains this weekend, but the wife has bronchitis, and I may be next. Boo! Especially because we got a lot of new winter gear to test out.

how heavy are those hothands? ... how many will you need for a trip?

now consider that a light synth overbag/quilt weights ~400g or so ... and itll prevent your down bag from getting wet ... it will also add a solid 10-20F to you temp rating ... and you can use it in the summer

not to mention you wouldnt be throwing away the hothands after every use

hmmmmm ;)

Why not just boil some water for your water bottle then stick it in your bag? You can get it warmer than any number of Hothands.

Interesting idea, but, no, it wouldn't dry the bag much. As others have commented, you need the moisture to GO somewhere else. With heat and no air flow, you will evaporate some of the water, but that water vapor will only travel to a colder, distal layer of the sleeping bag and condense there.

I know from much personal experience (smuggling frozen seafood across state lines) that even a few layers of fleece are impressively effective at keeping hot or cold food hot or cold for hours. The inside of the stuff sacked sleeping bag would still be warm 14 hours later, but only warmer, not dryer.

To dry a bag, get it into the sun. It is impressive what that 1 kWh/square meter sunlight will do. And, with the bag open, you get the ventilation you need to evaporate the water from the warmed bag. If it is cloudy or rainy, or you need to get hiking, stuff it and hike. Watch for sunny times through the day and drape it over a rock at lunch or over you pack as you hike.

This makes me wants to calc the output of those iron-salt-water-wood shavings hand warmers and report it in watts. It is obviously vastly less than a 100-watt bulb. Ballpark: about 5 watts? A sleeping bag in the sun can potentially absorb much of the 1000 watts of solar energy landing on it.

Hmmmm, interesting numbers with the watts, David.

Report back if you measure those hand warmers!

Sleeping human body emits 50 Watts/square meter = 75 Watts

As long as it's above maybe 20 F so it doesn't freeze inside bag it will dry out

I have used Joshua's method when I got rained on hard cowboy camping. I didn't think I'd need to pitch the tarp.
I packed up my damp bag when I hit the trail, with the idea that I'd take it out and air it in the sun when the sun comes out.

Well it rained all day so I never got that chance.

That night I set up camp as usual, with the tarp set up this time. Spread out my bag and inserted two water bottle filled with hot, but not boiling water a couple hours before going to bed.

The bag was much drier when I went to bed. I was able to fluff the down back to almost full loft.

Interesting idea, but think of the wattage and airflow in dryer, or even out in the sun with a very light breeze.