Gelled alcohol is a common fuel used for small, portable stoves and heaters. It has the advantage of being safer than liquid alcohol because it burns slower and doesn't spill a pool of flaming liquid when tipped over accidentally. It doesn't burn as hot as other portable cooking fuels, however, so it won't boil water very quickly. Gelled alcohol can be purchased under the brand names Sterno, Heat-It, Safe Heat, Easy Heat, to name a few. It is also possible to make your own gelled alcohol by mixing alcohol with calcium acetate (C4H6CaO4)
Mix 25g of calcium carbonate (chalk is a good source) with 100ml of vinegar. Stir with spoon for 5 minutes, or until most of the chalk is dissolved. If you are unable to weigh out the chalk precisely, don't worry. Keep adding it until it won't dissolve anymore. The excess will be filtered out. The acetic acid in the vinegar (CH3CO2H) is reacting with the calcium carbonate (CaCO3) to form carbon dioxide (CO2) and calcium acetate (C4H6CaO4) with excess water (H2O) and chalk (CaCO3) left over.
Filter the excess chalk using a funnel and coffee filter. Place the funnel over a jar and put the filter paper inside. Pour your solution through the funnel.
Evaporate the excess water. Mark the level of the liquid in your container. You want the final volume to be about half of that. Place the jar in an oven on low heat, or out in the sun. You may also evaporate all the water, but you will have to add more later.
Add 30ml alcohol to your solution. Do not stir the solution. You should be able to see the gel forming. Once the gel is completely formed, pour off any excess liquid fuel. If you evaporated off all the water in the previous step, add 2 parts water for each 1 part solid calcium acetate, then add the alcohol to this solution.
It will be difficult to transfer the gelled alcohol fuel into a new container once the reaction has occurred, so make sure you mix the alcohol and the calcium acetate solution in the container you want to hold your fuel.
When lighting your fuel, be very careful that none of it has spilt on your hands or on the sides of the container.