Magic Gel Reusable Handwarmer

The S&A Hand Warmers generate heat through exothermic crystallisation of supersaturated solutions and are usually reusable. They can be recharged by boiling the warmers and allowing them to cool. Heating of these pads is triggered by snapping a small metal device buried in the pad which generate a nucleation centre to initiate crystallisation. Heat is required to dissolve the salt in its own water of crystallisation and it is this heat that is released when crystallisation is initiated.
A sodium acetate heat pad is a reusable heat reservoir. It contains a supersaturated solution of sodium acetate (CH₃COONa). Crystallization is triggered by flexing a small flat disc of notched ferrous metal embedded in the liquid. Pressing the disc releases very tiny adhered crystals of sodium acetate into the solution which then act as nucleation sites for the recrystallization of the remainder of the salt solution. Because the liquid is supersaturated, this makes the solution crystallize suddenly, thereby releasing the energy of the crystal lattice.
The pad can be reused by placing it in boiling water for 10-15 minutes, which redissolves the sodium acetate in the contained water and recreates a supersaturated solution. Once the pad has returned to room temperature it can be triggered again. Triggering the pad before it has reached room temperature results in the pad reaching a lower peak temperature, as compared to waiting until it had completely cooled.

The S&A rechargeable hot-gel hand warming pads are ideal for winter walks, fishing and skiing. Also ideal for stargazing, or at sporting events, the S&A Exothermic Hand Warmer is convenient, reusable, and made from nontoxic materials. Other applications include snowshoeing, cross country, CX touring, crosscountry, xcountry, skiing, Nordic, touring, hiking, camping, survival training, disaster. Unlike the disposable hand warmers, these S&A Exothermic Hand Warmer are reusable hundreds of times.

Features:

• Each pad will provide up to 45 minutes of warmth
• Heats up to 55 degrees C (130-degrees Fahrenheit in just 15 seconds
• Sodium acetate and water are activated by bending a metal disk inside the pouch
• Recharge by placing in boiling water for 15 minutes, and then allow cooling
• With proper care, these hand warmers can be recharged over 100 times
• Environmentally friendly

The Pocket Pad is small and convenient enough to take with you wherever you go. Ideal pocket size to warm your hands, hat, helmet, or even relieve aches and pains. The small pads are fun to play with when holding it in your palm; a great gift for adults and children.

A Customers' testimony:

The S&A Reusable Hand Warmer from Surplus and Adventure struck me as brilliant upon first impression. I couldn’t understand how this item worked at first when I saw the metal disk suspended inside the melted sodium acetate/water liquid mixture. I touched the metal disk thinking that this must be the activator. I squeezed the disk from either side and nothing happened. Then I bent the disk and suddenly I had just started a beautiful chain reaction that created an immense amount of heat. In less than 15 seconds the reaction had stabilised into a crystalised structure which had 15 seconds prior been a water-like liquid. My next question was how this product was reusable. I looked on the back of the package it came in and the product claimed that if I boiled the hand warmer in water for at least 6 minutes the product would return to its liquid state and would be ready to be reactivated when cooled. This was just too much for me to handle. My friend and I both decided to get one.
I went home, got water boiling, dropped the hand warmer in and in 10 minutes my hand warmer had returned to its liquid state. The hand warmer needs to be wrapped in some sort of cloth while boiling because the shell is made of plastic, which is prone to warping with contact to the bottom of the pan. The crystals also have to be completely dissolved or else the reaction will occur as soon as it starts to cool. Crystalisation is really the key to these hand warmers. The bending of the metal disk gives a tiny space for the sodium acetate to separate from its normal latice and begin to form a crystal latice which leaves you with the hot, solid crystalised sodium acetate. If the sodium acetate is not completely melted down and there are still some visible solid white chunks, the reaction will quickly begin to occur again.
I activated the hand warmer and left it sitting on a wooden table and then collected temperatures every 15 minutes for an hour which are as follows:

• Temperature after immediate activation: 130°F (55°C)
• 15 minutes: 130°F (55°C)
• 30 minutes: 115°F (46°C)
• 45 minutes: 101°F (38°C)
• 60 minutes: 94°F (34°C)

As the measurements demonstrate, the temperature drop was fairly inconsistent. This factor can be avoided by insulating the hand warmer in say a jacket pocket or sleeping bag, but my test was to measure how long the warmer retains heat in open air.
Once I tested this product at home, and knew in confidence that it worked, I brought it with me on my next hiking trip. The plastic pouch is fairly thick, so I didn’t pack it any differently than any of my other random loose items. This weeklong trip was spent in the Natahaila National forest during fall months. The temperatures never got lower than 40°F (4°C) on this particular trip, but the hand warmer was a lovely addition even in these comfortable temperatures. I primarily used the hand warmer at night, putting it in jacket pockets, and I would then throw it in the bottom of my sleeping bag before I went to bed.

I typically boil the warmer in with the morning meal. This system is easy to do and doesn’t require me to do any extra work than I usually do. Again, as I said before, the product should be wrapped in some material so it doesn't warp on the bottom of the pot. Because of this, I must choose to either carry a material with me for this purpose or just hope to find something on the trail. I usually just put it on a stack of leaves or something in the boiling water, but I can’t assume that everyone doesn’t mind having leaf chunkies in their breakfast. My warmer has been slightly warped because I am not always careful, but the warping hasn’t caused any leaking on my particular warmer.
I have taken the hand warmer on numerous other trips that didn’t get colder than 40°F (4°C), but in February of this year I took the hand warmer to Pisgah National Forest where the temperatures at night were around 15°F (-9°C). In these temperatures the hand warmer really made a difference. It stayed warm for at least an hour. Keeping the hand warmer insulated adds to this time. I couldn’t keep my feet warm no matter what I did until I threw the freshly activated hand warmer into the bottom of my sleeping bag, rated to 20°F (-7°C) and let it warm up the bottom of my bag. My feet were in heaven. It also added a noticeable warmth to my whole sleeping bag.

Things I like:
Lightweight
Cheap
Adds significant warmth and comfort
Easy to use

Things I dislike:
Having to wrap warmer in material to avoid bottom of pot
Can get almost too hot initially to comfortably have on skin

Overall: I highly recommend this product. I have had no significant problems with the product and the price can’t be beaten.

John Bowerman

Applications

Sodium acetate is used in the textile industry to neutralize sulphuric acid waste streams, and as a photoresist while using aniline dyes. It is also a pickling agent in chrome tanning, and it helps to retard vulcanization of chloroprene in synthetic rubber production. Sodium acetate is the chemical that gives salt and vinegar chips (crisps) their flavour. It may also be added to foods as a preservative; in this application it is usually written as "sodium diacetate" and labelled E262. As the conjugate base of a weak acid, a solution of sodium acetate and acetic acid can act as a buffer to keep a relatively constant pH. This is useful especially in biochemical applications where reactions are pH dependent. Sodium acetate is also used in consumer heating pads or hand warmers and is also used in "hot ice". When sodium acetate trihydrate crystals (melting point 58 °C) are heated to around 100 °C, they melt. When this melt cools, it gives a supersaturated solution of sodium acetate in water. This solution is capable of supercooling to room temperature, well below its melting point, without forming crystals. By clicking on a metal disc in the heating pad, a nucleation centre is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted. The latent heat of fusion is about 264–289 kJ/kg.

Function

Many episodes of pain come from muscle exertion or strain, which creates tension in the muscles and soft tissues. This tension can constrict circulation, sending pain signals to the brain. Heat application eases pain by:

• dilating the blood vessels surrounding the painful area. Increased blood flow provides additional oxygen and nutrients to help heal the damaged muscle tissue.
• stimulating sensation in the skin and therefore decreasing the pain signals being transmitted to the brain
• increasing the flexibility (and decreasing painful stiffness) of soft tissues surrounding the injured area, including muscles and connective tissue.

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