Home made hand warmer trouble

[curiosity]

Hey guys,

 

I'm having some trouble with making some home made hand warmers.

 

The basic idea is that you put iron filings, salt, sawdust, activated charcoal, maybe vermiculite, and water in a bag. The water rusts the iron iron and creates and exothermic reaction, which creates heat. The salt accelerates the reaction. The charcoal distributes the heat and maybe accelerates, too. The sawdust just sort of absorbs the heat to make it last longer and gives it some substance. The vermiculite also distributes heat.

 

But I'm not getting any heat. I've tried several "recipes" and have messed around with the ratios like a half a dozen times, but I'm not having any luck. I'm really not getting any heat at all. Any idea what the problem could be?

 

I've tried these:

 

http://www.education.com/activity/article/warm-hands-iron-rusts/

http://www.hometrainingtools.com/homemade-hand-warmers/a/1650/

 

plus a bunch of different other guides on other sites. haven't tried the water gel powder, but that's not an ingredient in most of the recipes i've seen. Really, just salt, iron, and water should do the trick. It should get REALLY hot, in fact, but I'm getting nothing. What's the problem? I can only guess that it's the iron? I've already contacted the iron filing supplier with my inquiry

[alpha2cen]

How about thinking about these conditions again?

1) Iron particle size. The particle size is too large?

2) Charcoal property.

Charcoal is an important material for the oxygen supplier. To occur that oxidation reaction, sufficient oxygen must be supplied to the iron surface.

And, always watch out, dust explosion!!!

[curiosity]

These are the iron filings that I'm using:

http://www.teachersource.com/product/iron-filings-1-pound-package/electricity-magnetism

 

Hard to see from that picture, but they're really rather small. I'd almost call it iron powder. And I've read that people have had success with regular shavings even to the size of regular steel wool, so I don't think that's the issue.

 

Here's the carbon/charcoal i'm using:

http://www.petco.com/product/5217/Marineland-Black-Diamond-Premium-Activated-Carbon.aspx

 

It's granulated when I buy it, so I have to crush it myself, and it's not a perfect powder. Maybe I'll try making sure it's crushed further, but, again, I don't think that's the problem unless there's some serious chemical difference in the compound, and I've been assured that there isn't (I must have really annoyed the guy at the store--made him talk to me about it like 3 times to make sure that carbon=charcoal).

Tahnks for your help, though, alpha.

 

Anyone have any experience making these or playing around with these ingedients/reactions?

[alpha2cen]

The experiment was carried out at the room temperature?

[Enthalpy]

I haven't played with them but read the description on commercial ones, and they mentioned only iron, water and salt.

 

To make the reaction fast, I'd say it takes enough salt and a well-rusting iron, not too pure, with little chromium, aluminium and silicon. But that's just a guess.

Edited January 30, 2013 by Enthalpy

[dirtyamerica]

I remember reading somewhere about hand warmers made with calcium oxide.

( http://en.wikipedia.org/wiki/Calcium_oxide )

 

Maybe the above link will help.

 

be safe

[Enthalpy]

Calcium oxide is very corrosive to the skin. Strong advantage to iron.

[dirtyamerica]

Calcium oxide is very corrosive to the skin. Strong advantage to iron.

I agree as I work with it frequently (water treatment).

 

The essence of the hand-warmer I once read about and mostly forgot was that a CaO packet is sealed from the atmosphere in its packaging. Once you open the wrapper and knead the warmer the oxygen reacts to the Cao, releasing heat. The calcium hydroxide doesn't leak out of the package because (I forget).. I'm not too helpful but I tried!