[Mike526]

Hey everyone! I am very interested in the chemistry of hand warmers so one day I decided to create my very own warmer from scratch! However when i tried this experiment it didn't work very well. After doing some research I learned that all air-activated warmers are composed of 47%-70% iron fillings, 15%-35% water, 3%-9% vermiculite (or another water holding material), 5%-12% activated carbon, and 0.5%-4% salt (all these values are taken from the patent of the original hand warmer). I bought all the materials on amazon and after they arrived I performed my experiment. I got excited because my hand warmer did warm up. However I also compared it to the store bought warmers and the store bought ones were much hotter. When I measured the peak temperature of my warmers they reached about 90 degrees Fahrenheit where as the store bought ones reached a whopping 140 degrees Fahrenheit. This led me to wonder as to why the temperature difference was so large. I used all the same materials in the same quantities so why is my warmer 50 degrees colder? Is there anything i can do to make my hand warmers hotter?
Thank You

[Arkcon]

The difference if very likely a trade secret, but we could work  on trying to figure out improvements.  You say you have all the correct chemicals, but are they pure enough?  Likely they are, but its worth a check.  You have a range of percentages, did you try them all?  Or at least the lowest range, the highest range, of each ingredient.  You can plot all that out on a table, and see the temperature differences.  Building such a table is what science is about.  Its not all just cool observations -- chemistry depends heavily on this sort of math.

[mkurek]

^^ Arkcon got it dead on. But I have a question to raise with you as well. You said that the hand warmer is air activated, so how well is your air flow compared to the store bought handwarmers?