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Picture of Sodium Acetate BODY Warmer
HandWarmer.jpg
Have you ever gone to a football game and frozen your butt off?   While at the game you happen to have brought those little charcoal throw away handwarmers.   You pull it out, open it up, and shake the daylights out of it trying to get it to produce some heat.   Normally the amount of heat you get by shaking the bag warms you up more than the little bag ever will.    The last football game I went to was 30 F so I took one of my body warmer along and it produced 5+ hours of heat!  If your looking for a better solution to help keep you warm during those freezing football games (or other cold outdoor activities) then this is the instructable for you. 

Uses I have found for the body warmer.
1.  Cold football games.
2.  Cold campouts.
3.  My wife takes them to bed with her.
4.  Long lasting localized heat for injuries or sore muscles
5.  Cold car rides to and from work
6. ect.

I have quite a few reasons for making this instructable (explained in later steps), but my main reason is I can't find any instructions anywhere else on how to make a sodium acetate hand warmer from beginning to end.  I want others to share my passion and help me come up with ways to make these body warmers better.   Ultimately I feel the best way to get more ideas flowing on the subject is to put an instructable together that described how to make a decent sodium acetate body warmer.

If you would rather watch how to make it than read it, then go to this youtube video.  (Note: I doesn't include instructions on how to make the insulated bag).
http://www.youtube.com/watch?v=SNF2DO6EXcw
 
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Step 1: Motivation For making this instructable

I have a few reasons for making this instructable. 

1.   I think that Sodium Acetate hand warmers are AWESOME and that everyone should have one.  Unfortunately there are quite a few places that show you how to make sodium acetate, but all of them fall short in showing you how to make a decent hand warmer out of the sodium acetate solution.   Those instructions are missing how to make the clicker / activator,  the proper constancy for the solution, and materials that work well for a sturdy durable bag. 

2.   I want to better understand how the clicker / activator works so that maybe I could make a better one.   I have heard vague suggestions on how it works but have not yet as of yet read a good article about how exactly it works.

3.  I want others making these hand warmers and giving me suggestions on how to improve on this design.   For example, I use vinyl for my bags, but vinyl becomes brittle in cold temperatures.   I went camping with scouts in February one year and it was below 0 F.  After we were done using the bags in the morning I was collecting all of the warmers and putting them in my duffel bag.   I happened to throw one of the warmers into the duffel bag and it shattered the plastic on three of the warmers.

4.   Ideas and examples for better accessories.   I have made a few accessories for the hand warmers over the last few years.  One I have included in this instructable is the insulated bag.   I would like a way to keep the insulated bag close to my chest without having to hug it.   I would like a way to easily put the hand warmers into my gloves.

5.  The biggest drawback to sodium acetate hand warmers (ESPECIALLY the large Body Warmers) is how long they take to boil in order to recharge them.   I would like new ideas on how to reheat / recharge the bags.   I have tried heating the bags in 300 degree oil  (that worked until the bag split a seam),  I have tried putting a metal plate in the bag and heating it with an induction cooker.  I had some small success with the cooker, but ultimately it proved difficult and painful (I melted through lots of bags,  rusted out metal plates, and fought with an induction cooker until I gave up).   Another idea I have yet to try is to integrate an internal heating element.

Step 2: Activator / Clicker

The Activator (Clicker) is what makes it possible to make a body warmer in the first place.   The Activator starts the crystallization process thereby releasing the stored heat.   It is easy to start the crystallization process using a seed crystal, but it is impossible to provide a seed crystal in a sealed bag.   I have search all over the internet for the commercial version of these discs but they are difficult to find.  The few times I have been able to find them I would have had to buy them in bulk (1000 at a time).   Since this is cost prohibitive I made my own.

The activator is nothing more than a piece of spring steel with a couple of slits punched into it.  There are a few different places you can easily / cheaply get ahold of spring steel.   The two that I have found readily available is a slap bracelet and a tape measure.   I have tried both and have found that the slap bracelet is better.   The steel in a tape measure is flimsy and wears out quickly.   The steel in the slap bracelet is much thicker and lasts for a few years inside the bag.  You should be able to find slap bracelets at most party stores or Wal-Mart for less than a dollar.

Supplies needed to make the Activator.

1.  Slap Bracelet
2.  De-Solv-it (or some other solvent)
3.  Scissors
4.  Cardboard
5.  Razor knife
6.  Hammer

Start by removing the fabric / plastic coating on the slap bracelet.   I accomplished this on my fabric bracelet using a razor knife and fingernails.   With the razor knife I cut lengthwise down the center of the bracelet.   Once cut I started at one end and used my fingernails to remove the fabric over the top of one end.   Once I had the fabric off one end off I was able to pull hard on the fabric toward the other end and it came off in one large chunk.   You can watch a better description in my video if you need one.

Once the coating is removed there is a glue residue left behind.   Use the de-solv-it to remove the residue.   Wash off the de-solv-it and the glue.  This should leave you with a gleaming metal slap bracelet.

Now, take your scissors and cut off a square of metal.  Take the square you cut off and round the corners with the scissors.  Finally check for any sharp points on your metal and cut those off.   You are rounding the corners and cutting off the points so that your metal disc does not puncture your bag.

Take your circular metal disc and place it on a couple pieces of cardboard.   The cardboard gives a soft background and allows the razor to puncture through the metal.   Being extra cautious (so you dont cut yourself) take your razor knife and using a lot of pressure, punch two parallel slits in the disc.   The direction of these slits should not matter.  You are trying to make these slits grind / touch each other when the disc is clicked.   Right now the metal around the slits is bent outwards and needs bent back in.   Place the disc on a hard object and pound it flat with the hammer.

And voila!  We have ourselves an activator.



Step 3: Vinyl Bag

Lets make our bag.   I have tried a few different types of bag material.  Some include zip-lock freezer bags, vinyl, 6 mil painters tarp, and one other that I don't remember the name of.   The zip-lock did not last very long before it punctured, the painters tarp melted, the other plastic worked well but seemed prone to getting really small holes.   (If you get even the smallest hole in your bag, the sodium acetate will not stay in solution form).  So far the best plastic I have found is thick vinyl from Wal-Mart (or fabric stores).  Vinyl is cheap, available, and comes in much thicker sheets than the other plastics I have tried.  

While vinyl does have its upsides, it has one major downside.   In very cold temperatures it becomes brittle.   I broke a few of my bags after using them in sub 0 temperatures.  For this reason I would like to try other types of bags.   Some types of plastic I would like to try are 1.  The plastic used in Hydration Bladders (Camelbak).  The problem is I don't know where to get this type of plastic.  2.  Silicone bags.  I am not sure how to seal this type of bag.

If you have any insights for better plastic bags I would love to hear about it.

Enough talk, lets make the bag.

Tools
1.  Scissors
2.  Sealer
3.  Permanent markers
4.  Flat iron (Alternative to Sealer)

Supplies
1.  Clear Vinyl
2.  Metal Disc

Take your vinyl and fold it in half.  Take your scissors and cut a square out of both halves of the vinyl at the same time.   Trim the edges of the vinyl to make yourself a nice looking rectangular bag.   Depending on how much sodium acetate you have will decide how large you should make your bag.  My bag was 10 1/2" by 8"

Next put your favorite sports logo or design on the inside of the bag (for me thats BYU).   If you color on the outside of the bag those colors will leach out and stain your counter when the bag is hot (even though you are coloring with permanent markers).   Draw, trace, or scribble with permanent markers a design on the inside of the bag.  Dont forget that since you are drawing on the inside you need to reverse your letters.   (It would be a good idea to test to make sure your marker really is permanent.   Draw with your permanent marker on a scrap piece of vinyl and then run it under water to make sure it doesn't come off.   I had a marker that said it was permanent that washed off when I put the sodium acetate inside).

Now take your sealer and seal all four edges of the bag.  For my heat sealer I set it up to 9 seconds heat time for thick vinyl.  You will have to experiment to find the right amount of time for your vinyl and sealer.   After the 9 seconds I let the vinyl cool before trying to pull it off the sealer   If you don't let it cool you will stretch out your seam and it will create a weak point in your bag.   Note:  You can test to see if you have a good seal by trying to pull apart the seam.   If it pulls apart you didn't do it long enough.  It should tear before it pulls apart.    

Last, cut off one corner of your bag big enough to fit your metal disc, then insert your disc.   I do it this way is so that when I add the hot sodium acetate to the bag, there is less area to seal.



If you don't have a sealer I have successfully sealed bags using a flat iron.  IF you decide to try the flat iron instead of a sealer, first don't hold me responsible if this process ruins it.  2nd, either get permission to use it (they can be expensive) or buy a cheap one from walmart.  3rd, be careful, those flat irons are hot.  I take no responsibility.   It is hard to tell how hot to make the iron in order to melt the vinyl together.   Experiment with it and come up with the right heat/time/pressure for yourself.  (As said above try pulling apart two pieces that you seal.  If it comes apart then it wasn't good enough.  You want it to rip before it comes apart).   Once you have made your bag I would recommend that you fill it with water, seal the bag, and stand on it to make sure your seals will withstand the test of time.  If it passes then cut the corner and let the water out.

Step 4: Prepare The Sodium Acetate

Now onto the Sodium Acetate Solution.

You can either mix vinegar and baking soda in the proper proportions to make your sodium acetate or you can buy it online or at a chemical shop.  I have mixed my own before and it worked quite well but it took FOREVER and stunk the house up.   It would take a long time to make enough sodium acetate to fill a large bag.   There are a number of sources for sodium acetate such as where I bought it here -- http://www.hvchemical.com/ -- which is local to me.   I have also seen it on ebay for fairly good prices.   You want to buy Sodium Acetate Anhydrous.   We are making Sodium Acetate Trihydrate when we mix it with water.

Tools
1.  Pot
2.  Measuring Cup
3.  Tool to pound out the lumps (I used a meat pounder)

Supplies
1.  Sodium Acetate Anhydrous
2.  Water

The ratio of Water to Sodium Acetate is approximately 1 cup water to 1 1/4 cups sodium acetate.    For my larger bag I used 2 cups water to about 2 1/2 cups sodium acetate.  

So add your water to the pot and bring it to a boil.  Then add your sodium acetate.  Stir and pound out the lumps until everything has disolved.   At this point your solution should be near boiling and there should be a super thin crystalline layer across the top of the solution.   You want your solution right at the point where this layer appears.  You can play with the consistency by adding more water,  boiling water off, or adding more sodium acetate.

If you make the solution too thin then the heat reaction wont be as strong.  So it will still crystalize and get hot, but it wont get as hot or stay as hot as long.

If you make the solution too thick then your solution will look like a gel when cool.   It also has a tendency to form interesting crystals in the solution when it is too thick.  These two side effects can actually be pretty cool, and don't seem to change the heat reaction.

Step 5: Testing your solution and activator (optional)

I added this step for those of you who are impatient and want to see results NOW!!!   So lets give you your results now.  Simply put we are going to create a temporary hand warmer.

Tools
1.  Measuring Cup
2.  Bowl full of ice water

Supplies
1.  HOT sodium acetate solution
2.  Freezer Zip-Lock bag
3.  Clicker / Activator

Open your ziplock bag and insert your clicker / activator.   Take the measuring cup and put some of the sodium acetate solution in the bag.  Seal the bag and then place it in the ice water.   Leave it there until it has cooled off.   Once cool pull out the bag and try out your clicker.  INSTANT HEAT.   USUALLY.    Sometimes the clickers are temperamental and take a little more effort in order to activate your solution.   If needed click, twist, and/or bend your activator until you get the reaction to take place.   

Step 6: Finish the Hand Warmer

Picture of Finish the Hand Warmer
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Finally we are ready t put the solution in the bag.

Tools
1.  Funnel
2.  Container for pouring the sodium acetate.
3.  Leather Gloves
4. Sealer
5. Wet Paper Towel ( or rag)

Supplies
1.  Hot sodium acetate
2.  Vinyl bag with one edge cut and clicker / activator inside.
3.  Food Coloring (optional)

DISCLAIMER:  While I wouldn't consider making a body warmer very dangerous, if there were a dangerous part this would be it.   The solution is VERY hot and can burn you.   If you get the solution on you it will initially burn because it is hot, but then it will also crystalize and continue to burn.   Just be ready to run to your sink and wash off the sodium acetate if you happen to get it on yourself.   Also, the bag and the funnel will get very hot when your pouring the solution into the bag.   I would recommend using gloves during this part.

Step 1, transfer the solution from the pot into something that is easier to pour with.   This step isn't necessary but I find that pots have a tendency to drip the solution down the bottom of the pan instead of into the funnel.

Step 2,  insert the funnel into your vinyl bag.  hold the funnel in the bag with your fingers.

Step 3,  pour the solution down the funnel and into the bag.  Note don't overfill the bag, this makes it incredibly hard to seal the bag.   I wouldn't fill it more that 1/2 to 3/4 full.  Remove the funnel.

Step 4,  If you want to change the color of the sodium acetate now is the time to do it.   Add drops of food coloring to the bag.   It might help to experiment with water first to know what color you want to create.

Step 5, Any sodium acetate in the area of the final seam (crystalized or not) will prevent a good seal.   When you seal the bag the water evaporates and the sodium acetate crystalizes in the seam.   I prevent any problems by wiping out the seal area with a wet paper towel.   Simply wet a paper towel and wipe the inside of the bag where the seam will go.   Make sure to do a good job cleaning the inside of that seam.

Step 6,  Force any excess air out of the bag  (making sure not to get sodium acetate in the area of the seam, a little air is ok) and seal the final seam.

And thats it, your bag is done.   You might put your bag in cold water so that you can cool it down and try it out.   Often times after you initially seal the bag the solution will crystalize and you will have to heat the bag up in boiling water to melt all of the crystals before testing it.

Step 7: ReHeating the body warmer

Picture of ReHeating the body warmer
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To reheat or reactivate your body warmer all you have to do is boil it.    Essentially what your trying to do is melt the crystals.  Sodium Acetate Trihydrate  (what me made with Sodium Acetate Anhydrous and water) melts at 58 C or 136 F.

Tools
1.  Pot of boiling water
2.  Strainer
3.  Tongs

Fill your pot will water and heat up the water.   Add some sort of barrier into the pot (a strainer, or a rag).   The barrier is to prevent the vinyl from sticking to the bottom of the pot and becoming too hot and melting.   Next add your bag to the water and put the lid on the pot and let it boil for a while.    You need to let it boil past the point where you can see any crystals (even little tiny ones).  Finally once it is all solution again take it out with your tongs and let it cool.

You can help speed up the melting process by taking the bag out of the pot and mixing the solution in the bag around.  This helps to distribute the heat inside the bag.

During the boiling process you can test the solution in the bag to see if it is completely melted by taking the bag out of the water and hold it up by one corner.   Then using a pice of ice cool down the corner of the bag you are holding.   If the solution crystalizes in that corner then it is not ready to take out.

Step 8: Insulated Bag

Normally the body warmers cool off fairly quick and only gives 30-45 minutes of heat.  To help the body warmer keep heat as long as possible and to slow down its heat loss I have created a bag to put the body warmer into.   Using this insulated bag and heating up the body warmer before activating it, I gotten 5+ hours of usable heat out of the body warmer.

Tools
1.  Razor Knife
2.  Scissors
3.  Permanent marker
4.  Hot glue gun

Supplies
1.  Mylar Bag  (you can use aluminum foil tape instead, but it takes longer).   I have bought these a a food storage center near my house for really cheap.
2.  Padded Envelope ( flexible packing foam is a good alternative)
3.  Duct Tape (of your favorite color)
4.  Velcro strips

Cut and seal your mylar bag so that it is just longer then the padded envelope and wide enough to just barely fit your padded envelope.   Insert your envelope into your mylar bag.  Cut the the top of the mylar bag off so that it is one inch longer than the inserted padded envelope.   Now cut off one side of of that top 1 inch so that it creates a flap at the top of the mylar bag that you can fold over to close the bag.

Draw a fairly large square on one side of the mylar bag.   This will be the window that allows heat to escape (and keep you warm).   Use the razor knife to cut out the square.  Be careful not to cut too deep, you only want to cut through one side of padded envelope.

Now take your duct tape and tape the inside edges of the window.   This will keep the mylar bag and the envelope from ripping.   The mylar bag edges are somewhat rigid and sharp so cover all the edges of the mylar bag with the tape.  

Finally cut out 4 strips of velcro. Hot glue two of the strips onto the outside of the flap of the bag.   Now hot glue the other two strips to the front of the bag so that you can fold the flap over and have it stay down because of the velcro holding it down.

Thats it!   Now you have a body warmer and a bag to keep it hotter longer.

Step 9: Tips/Tricks/Finish

Last but not least, a few tips I have picked up along the way.

1.   If you heat up your bag before you use it, it will stay hot MUCH longer.  
2.   If you heat up your bag and put it in the insulated bag it will stay hotter EVEN LONGER.  

The other day I went to a BYU football game where the temperature outside was 30 F.   Before I left for the game I boiled my body warmer to get it hot before I left.   So I left for the game at 7:00 PM.   While at the game I was nice and bundled and kept the body warmer in my coat pressed up against my chest.   It was nice and warm.   I ended up getting home from the game at about 12:15 AM and the body warmer was STILL HOT!!!   Not just warm, it was hot!   That is 5+ hours of useable heat.  Now thats what I am talking about!!!  

Throughout the game I was warm except by half time my toes were a little cold.   By the end of the third quarter my toes were very cold.   I happened to have another body warmer on me, so I took it out, activated it and placed it on my shoes.   That worked somewhat, so I took my feet out of my shoes and placed the warmer directly on them.  AHHH that felt good.   After 5 minutes of that, no more cold toes.

3.  If your body warmer will not stay in solution no matter how long you heat it up, this would suggest that you have a hole in your bag.   Even the smallest hole will cause your sodium acetate solution to crystalize when it cools down.


If you need more instructions here is a youtube video I made of the process.

http://www.youtube.com/watch?v=SNF2DO6EXcw
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Laral1 month ago

I see a lot of people trying to make their own sodium acetate with less than stellar results. Why would you bother? You can't make it any way near as pure as a chemical company can and purity is absolutely mandatory for this use. Impurities will interfere with the crystallization process. You can buy 4 oz. of 99% pure food grade sodium acetate on eBay for $8.95.

Laral1 month ago

I am playing around with sodium acetate and would like to make something like this. There are some good ideas here. Thanks.

ccronkhite4 months ago

Have you tried the vacuum sealer bags for preserving food? The bags we use seem to be pretty tough. It definitely holds up in the freezer and I'm pretty sure the material can stand hot temperatures too.

kevin_mic (author)  ccronkhite4 months ago
I have used them. They work for a little while. Eventually they stop working because tiny little holes form and cause tge solution to crystalize when cool.

If you have sodium acetate its worth trying those bags if you have them.
I see. I suppose those aren't engineered to stand up to repeatedly being heated and cooled and squished around.
ccronkhite4 months ago

Have you tried the vacuum sealer bags for preserving food? The bags we use seem to be pretty tough. It definitely holds up in the freezer and I'm pretty sure the material can stand hot temperatures too.

ccronkhite4 months ago

Have you tried the vacuum sealer bags for preserving food? The bags we use seem to be pretty tough. It definitely holds up in the freezer and I'm pretty sure the material can stand hot temperatures too.

peterscache125 months ago

Hi again.

I have made several attempts to make handwarmer bags, but all of them seemed to have problems. Firstly, I did come up with a way so that you don't need to cut off a corner. When you're sealing the bag, simply make sure there's an extra tab of parchment paper on one of the short edges. It needs to be just big enough to accommodate the end of the funnel.

I have tried both using the oven, and using a hair straightened. The oven seemed to work better, as I didn't need to unstick the vinyl and therefore risk making small holes.

However, having made homemade solution, my discs have rusted, and every single one has ended up snapping into pieces. I have thought about spray-painting the discs before I put them in, but I figured that the slits would just rust anyway, and that paint would just slow down the disc from being destroyed.

Any ideas? I would really like to try making several of these without using a heat sealer or buying solution. (Another possible idea for sealing I need to try- A heat gun and wooden board (similar to oven idea.)

kevin_mic (author)  peterscache125 months ago

One other thought. I have recently started playing with nichrome wire to melt foam. It might be possible to make your own sealer using the wire. Using the right gauge wire and volt input you could cause the wire to heat up to the exact temperature you want.

http://www.jacobs-online.biz/nichrome/NichromeCalc.html

kevin_mic (author)  peterscache125 months ago

When I made my first bag of sodium acetate I had the same problem with my clicker. For mine over the process of a year it rusted away. Ever since then I have made the solution by buying sodium acetate pre-made and haven't had this problem. I don't really know what is wrong, but here is my best guess.

I was talking with my neighbor about the problem (he teaches Chemistry at my local high school) and we both think that there is probably left over vinegar in the solution and that that is what is causing the clicker to rust. Question is how to remove that extra vinegar? I found this video that shows the guy cleaning the sodium acetate crystals using isopropyl alcohol. I would suggest you try that and see if it fixes your rusting clicker problem.

https://www.youtube.com/watch?v=AedL_NCv1Pw

momsih6 months ago

How about the reusable ice packs, they seem to hold up pretty well and you could put parchment paper between the iron and plastic which would at least protect the iron....I'll say SHOULD protect the iron

peterscache12 made it!6 months ago

Thanks so much for this instructable. I used to have a cheap promotional reusable handwarmer, but eventually it no longer would stay in liquid form. It wasn't until recently that I learned that you could make the solution at home with baking soda and vinegar.

And closely following the youtube video made by NerdRage, I was able to make two batches (2.5 cups) of sodium acetate trihydrate on the first try (I have another gallon of vinegar solution evaporating in the garage.) Like said by Creak, my solution was an apple-juice color, but I don't care too much, as it still works just as good. I really liked your instructions as they helped the solution become portable and usable with the vinyl and slap-bracelet discs.

The slap-bracelet was a pain in the butt. Mine had a rubber coating on it, and it took forever to get off. I now have the materials, but I was wondering if you had any tips for sealing the vinyl with a hair straightener.

I too, am LDS, and mine will most likely have a BYU logo on it. Once it's done, my Biology teacher is letting me bring it in to show to the class. Thanks for the useful winter DIY.

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kevin_mic (author)  peterscache126 months ago

My first hand warmer I made my own sodium acetate with vinegar and baking soda. It also looked like apple juice. It worked great but I did notice that it caused the metal disc to rust whereas buying sodium acetate my disks never rusted.

For sealing bags --

A few years ago I played around with making the vinyl bags by trying to seal them in the oven. I cut out two square pieces of vinyl (both sides of the bag) then I cut out a square piece of paper that was smaller than the vinyl squares. Next I put the first piece of vinyl down, then the paper then the second piece of vinyl. The paper prevents the vinyl in that area from sticking together. I then tried to remove all air bubbles from the edges where vinyl was touching vinyl. Last I heated up the oven to 300 degrees and put the vinyl on a cooking sheet in the oven for a few minutes. (watch it to make sure it doesn't smoke or melt or burn). From there I would cut the corner off the bag and remove the paper. This will make it so you only have to seal one corner with a flat iron.

When you pull it out of the oven (while it is still really hot) it might be a good idea to press the edges together with something (pizza cutter?) to try and form a better seal.

If you decide to try this, fill it with water for your first bag and pressure test it to make sure it works. If you try it I would love to know how it goes for you.

One other idea, you might check with your ward or stake food storage specialists. They often have access to heavy duty sealers used for sealing mylar bags. You might be able to borrow one of them to make your bags.

I first tried sealing the vinyl with a hair straightener, but it was too hard to keep the solution out f the final seam. Otherwise it was watertight. I had some better success by melting the vinyl your way, in the oven. I actually had to heat the oven to 345 degrees to melt it to the point I wanted. I've only made a small one for now, but hope to create a 6 x 4 one before long. However, last night my handwarmer activated accidentally when it was jostled in the car. I wonder if the metal actually clicked, or if you actually need to let it cool undisturbed. I hope there isn't an air leak.

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AndrewF56 months ago

I live in Provo and was wondering if there was anywhere closer I could go to get some sodium acetate? Also, how many pounds or grams do I need to make 2 or 3 small bags? I have been able to find decent prices online, but the shipping is more than the chemical! I would make it myself from vinegar and baking soda but my wife can't stand the smell of it so I will have to get some sodium diacetate premade.

kevin_mic (author)  AndrewF56 months ago

Hi valley chemical up in centerville has it. That is the closest place I know of. You wont need very much if all you want to do is make a couple small bags. 1 or 2 pounds would probably be plenty. If you just want a sodium acetate hand warmer just buy some on ebay or amazon. You wont save a ton of money by making them yourself.

AndrewF56 months ago

PS I've also heard you can use an alligator clip to create a nucleation site. I haven't confirmed this yet, but another reference said it works!

Creak6 months ago

I began making one before I found this instructable. An unfortunate mistake as I made the sodium acetate from scratch rather than purchasing it. The solution turned the color of apple juice after heating (even though I used white vinegar).

Regarding a container: I successfully used a small sprite bottle as my hand warmer. Although it is not flexible, I believe it will be very durable. To create a nucleation site I simply added two ball bearings. When shaken they strike each other they create a nucleation site and cause the solute to precipitate. Super easy!

Problems I experienced: bottle warped when placed in boiling water, lid stripped when tightened hot, layer of crystals formed even when in boiling bath (too much air space?)

kevin_mic (author)  Creak6 months ago

Thanks for the tip with the ball bearings. I had no idea that would work.

As for crystals forming even when in the boiling bath, is the bottle sealed when this is happening? How full is the bottle? I have found you have to have the liquid in a sealed container for it to work. If the bottle is sealed and everything is melted but a fine layer on the surface then I would try taking the bottle out of the water and shaking it up and down. (Be careful when doing this, I don't know if it will cause the lid to pop off). I find I have to do this with my bags to make sure super fine crystals in the corners of the bags are melted. By shaking the bag it helps to heat up all parts of the bag evenly so that absolutely all crystals are melted.

Thanks for your comments.

looop451 year ago
Wow it only gets that cold i Utah.
kbuechel1 year ago
Idk if this has been mentioned , I seen the comment regarding iv bags but what about new bladder bags ? like the kind that hook up to caths . I used to work in healthcare abit and can contest to the new ones being very strong . Don't know how expensive they are but I would assume they are readily available at any local medical store ... and thanks for the great write up :)
kevin_mic (author)  kbuechel1 year ago
I did some quick searching on bladder bags and cant find any very cheap. I did recently get some IV bags and am hoping to try them out. I am not sure how to get a metal disc through the small opening though.

If you try a bladder bag I would love to hear how it works out.
Help I can't get past the mushy stage. What am I doing wrong. I didn't do the carbon stage, do you think that is the reason?
kevin_mic (author)  nannysaunders011 year ago
I am not sure what you mean by mushy stage or carbon stage. Can you give me more details on what you are trying to do? Are you trying to make sodium acetate from scratch?
Just as a precaution can I warn anyone who is wondering whether to try a microwave to heat one of these - NOT TO TRY IT! All you get is an incredibly expensive Aurora Borealis effect in the cooker for about 10 seconds, then, that's it. No more cooker.
It's the metal clicker that has this effect, and boiling is so much safer and economical …
some microwaves can have metal in them. i can microwave things in a metal bowl with no problems.
One may have better microwave results by turning the power down. My family uses the adjustable level to allow thawing of semi-metallic cans, as well as better cooking for things such as broccoli. Thawing is usually just a level 2 or 3, plenty safe for juice concentrate. 4-6 will generally work for foods that like to sputter and pop, eliminating mess inside the cabinet.
I would warn to take breaks and knead the hot spots around.....easier to just boil.
lperkins3 years ago
If you want to get the mix more precise, use a thermometer as you're boiling it. The more concentrated the salt is, the higher the boiling point will be. My experimentation hasn't figured out the optimum yet, but if you have, you might take a reading and post it for reference.


What kind of sealers do you use to make the bags? I'm having trouble getting mine to not eventually come loose again.
kevin_mic (author)  lperkins3 years ago
I haven't used a thermometer, the thin layers of crystals on the surface is usually good enough for me. If you want exact results I think you would have better results using a hydrometer than a thermometer. I haven't tried either though.

As for the bags, I am using a heavy duty sealer that has a heat element both on top and bottom. Unfortunately even with this I have troubles like you have -- the seams blow out randomly.

I do have a different idea for making a bag that I have been meaning to post but haven't gotten the time. Basically you use your oven. First cut the vinyl for your bag. Second cut out a piece of thin fabric that is the same dimensions of the bag. With that fabric now cut 1/2 inch off all edges. Then place the fabric between the pieces of vinyl. This should make it so that the vinyl is touching the other piece of vinyl on all edges, but the center of the bag is vinyl fabric vinyl.

Now heat your oven to 350, place some aluminum foil on a cookie sheet and your bag on the foil. Then place it in the oven for 3 minutes (longer and the vinyl will begin to smoke). Pull it out. While still hot I have gone over the outside edges with a pizza cutter. Once cool, cut off a corner and remove the fabric. You will still have to use a different method to seal the final seam.

I have only created one bag this way, but so far the seams have held.
I have been wondering if a solvent-based vinyl glue would work well, but I haven't had time to find any.
acoleman33 years ago
now...will this get as hot as an mre heater? and if not....can you hack your idea to *get* it that hot?
kevin_mic (author)  acoleman33 years ago
No, it won't get as hot as that, and no you can't hack it to get it that hot. This isn't really a chemical reaction so much as a phase change reaction. You are getting heat when the chemical changes from liquid to solid. This change occurs around 150 F. So it really can't get any hotter than that.
bobtannica3 years ago
Very interesting instructable. Has anyone tried the IV bag route? How do you seal it?
heathbar643 years ago
this is cool! I mean hot!
I'll share what we use around the house. We make a cloth bag or use the sleeve off an old sweatshirt and fill it with about 4 pounds of popcorn. when you microwave this for about 3-5 minutes, it will warm your bed for several hours.
Hey Kevin...how cool...I have been playing with this technology all day yesterday at a Christmas Fair I was working at...in South Jordan at the equestrian center there...anyways...I came home and youtube searched to see if I could make it myself...(they were so expensive to buy) Saw your video..(realized you were a Utah brat too- Cougs! ) ....then I spent five hours trying to find pre-made metal clickers...thinking this would be awesome Christmas Gifts...(My family reunion is this Christmas and over 80 people will be there)....So I get the whole slap braclet deal...but I still would really like to buy a bunch premade...since I have to make almost one hundred for this party....and I am stoked that you said...you found them online for in mass quantities... do you remember where???...because I haven't seen any yet....Thanks!
What about a click style barrette? would those work?
kevin_mic (author)  SaratogaGirl3 years ago
I wish I could remember where I saw them. It was a couple years ago when I was searching for them and I only came across them once. It seems like it was on some Chinese website. I have searched since and never found them again. Sorry.
jsaunders53 years ago
Have you tried the "food saver bags"? They might work and if you have a food saver unit you can make the size you want and the unit will seal it too. They're made for the freezer.
I've been wondering how to do this for something like 20 years! Thanks for helping to satisfy my curiosity.

I have a simple idea for heating--so simple I thought someone would have mentioned it...but I haven't seen it here. My idea is to add some table salt to the water you boil it in to reactivate. This should have a lot of benefits/advantages:

 1. You've already chosen materials that are compatible with sodium acetate. Most likely, sodium chloride is also perfectly compatible with everything you're using.
 2. Salt is cheap and about as easily available as a material can get.
 3. Salt is easy to measure, so it'll be easy to do some trial and error and come up with the ideal ratio of salt to water.
 4. Salt dissolves easily in hot water.
 5. Salt is a good preservative. If the salt is concentrated enough, your boiling solution can be re-used many times without turning slimy or green.

All you have to do (if I'm right) is to keep using saltier water until the pack reactivates as fast as possible, stopping short of damaging your warmer. The water's boiling point is proportional to the salt concentration. When you find the right ratio, make a note of it, then make up a pot's worth of it. Find a jar or something to store it in between uses. When you're ready to reactivate, pour it back into your pot and boil as usual.

Remember that as the water boils, the salt will be left behind, so you will need to add more water to keep your salt concentration from creeping up. Maybe mark the inside of the pot you will use, then when you're done reactivating your hot pack, you can just refill the water to the pre-boiling level with cold tap water. Pour it back into your jar, close the lid and store it. 

What do you think?
kevin_mic (author)  sage instructor3 years ago
Interesting thought. I will have to give it a try and see how much it raises the boiling point.

I was also wondering what effect it would have in the solution. In water it lowers the freezing point, I wonder if it would have that effect in sodium acetate solution as well.
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