The BakePacker® is not a steamer. Each small compartment of the aluminum grid functions as a single, self-contained heat exchanger. When the water in these compartments is boiled, the rate of heat transfer from the water to the plastic bag is very high. Higher, in fact, than a steamer, double boiler or an open pot of boiling water. Thermal engineers refer to this process as "the heat pipe phenomenon." The ability to transfer very large quantities of heat with small temperature differences is the main feature characterizing the heat pipe.
The BakePacker, then is a cluster of heat pipes that move large amounts of heat at a relatively low temperature (212 degrees F at sea level). The net result is that you, the camp chef, can now bake many things including cakes, muffins and quickbreads in a simple cook-pot.
U.S. Patent No. 4,793,324
Canadian Patent No. 1304236