Homemade Hand Warmer

Maybe because there's no vermiculite? As I recall, vermiculite absorbs water.

You've piqued my curiosity. i found this:

Air-activated hand warmers work through the process of oxidation. When the sealed package is opened, air enters the tiny holes in the the warmer's polypropylene bag. The air interacts with the iron that is in the bag and creates iron oxide---rust.

In air-activated warmers, the bag traps moisture. Vermiculite in the warmer helps keep the heat from dispersing. Carbon may be included to help distribute the heat throughout the warmer. Salt is a catalyzing agent. Cellulose acts as a filler. Air-activated warmers can also contain charcoal and sawdust.

So, now I'm guessing that the problem is that the steel is already somewhat oxidized.

There is no visible sign of rusting. Perhaps the steel wool has a coating to slow down oxidation? I tried massaging the combination with the intent of overcoming this possibility but still no temp increase.

Most metals form a layer of oxidation quickly after being exposed to air, even though you can't see it. I suspect that's the problem here. I was surprised to find out that fresh un-oxidized aluminum ignites in water. But there you go.

Yes, I believe steel wool is coated with a very thin layer of oil to prevent rusting. Also, the surface area ratio may not be quite right. If you could completely clean the steel wool, (in lacquer thinner perhaps, maybe followed by a detergent, etc.) and then grind it up, I'd think you might have some success, provided the steel wool alloy is prone to rusting. Iron would probably work better.

I think the iron needs to be much finer than steel wool to have sufficient surface area

I think you are going to set yourself on fire!

Without vermiculite this will not work. The vermiculite reacts with the "air", heats up and reacts with the other items listed. The "old school" air filters we used in the mines in case of a fire contained vermiculite and other items. Once activated, the vermiculite would get very hot. I can not remember exactly what part of the "air" it reacts to, but the function of the filter we used, was to basically burn off everything except the oxygen, as we inhaled. The harder you breathed, the hotter the filter became.

Meaning no disrespect but I believe the premise of this post to be false.

Vermiculite is a form of clay, and is not a reactant per se in the device . One of vermiculites properties is exfoliation, or expansion when heated. As a clay it is relatively inert. In a commercial hand warmer pack, the particle size of all constitutents is carefully managed. The addition of vermiculite can be seen to 1) add bulk density to the powder mix and help prevent segregation of constituents;2) help absorb moisture from reaction; 3) possibly act as a governor to the reaction by swelling, thus reducing surface area of iron particles to air; 4) act as both an insulator to prevent burns and 5) act asa reaction moderator by physical dilution (spacing) to separate reactants.

If someone would like to post a validatable chemical reaction of 'vermiculite reacting with air' to form heat, I will appreciate the lesson.

milo

I believe You are correct. Vermiculite is used as an insulating medium, also used in gardening potting soil to keep mixture from packing.

oilcan13

Make sure that the steel wool wasn't stainless steel.

Also: Keep in mind that steel is made with iron. Pure iron (Fe) will be more reactive to oxygen then steel. Steel wool would be difficult to break into fine particles. The finer the more reactive. Think of kindling wood vs. a log.... only 10,000 times smaller. Wood gives off heat due to the same oxidation, just takes a little effort to get it started as compared to a hand warmer.

My wife and I put in an in-ground pool 3 years ago. The only part we did not do is the finish concrete work. We did have some very good friends over to help with the hard bottom material. We used vermiculite in the mix for the bottom material. I think the ratio was 2 bags portland cement to 1 bag vermiculite. The day after the pour the wife and I rubbed out the high spots left from the towels. The floor was very cool to the touch, initially. I stayed on my knees and she half sat down to make it easier on her back. She and I were both still sore and tired from the previous day. It was not long before we both had chemical burns from the floor material. I assumed it was from the portland cement and not the vermiculite. We had used gloves the day of the pour but did not think we needed any PPE since the bottom was "dry".

I am not sure if this helps or if it just adds confusion to the thread.

The oxidizing of the iron is what generates the heat.

The vermiculite is a clay as others have said. It is added to the mix to impede (control) the rate of oxidation and disperse the heat. Without this ingredient, there would be a very rapid chemical reaction (seconds rather than hours) which would result in burning temperatures.

Activated charcoal and a BBQ briquette are quite different. Activated charcoal is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms.

Caution: If you are able to achieve the exothermic reaction that you are looking for, exercise extreme caution before making hand and foot warmers because if the formula is not exactly right it might be too hot which could result in serious injury.

Thanks for reporting your findings! milo

I agree with Milo. I have thought about what it might take to make my own, though they are, for the number I would need to use here in Northern Virginia, USA (yeah, I know. THIS year it makes a liar of me!) it doesn't make a lot of sense to do it, at less than 1 $US each for hand or foot PAIRS. But for sheer scientific inquiry, I most definitely appreciate seeing your results. And for that, I gave you a GA.

Try Sodium Acetate heat packs.They are reuseable and last a long time.Someimes called Hot Ice packs.They can be activated by pressing a "clicker" inside the plastic bag, and can be restored by putting in boiling water till all crystals have melted.It is then ready for long term storage or till needed again.

HTRN

How to build a hand-warmer:

http://articles.sun-sentinel.com/2001-08-29/news/0108200398_1_bag-vermiculite-magnet-school