Abstract: One version of the invention provides a method for cooling and maintaining an object at a substantially constant temperature. The method includes adding a salt that dissolves endothermically in water to a mixture containing at least water, a surfactant and an emulsified thermal buffer. The "salt:water:thermal buffer" ratio is such that the reaction provides sufficient endotherm to cool the system to the freezing point of the thermal buffer and effect at least a partial phase change of the thermal buffer. Another version of the invention provides a device for effecting the method. The device has a reaction compartment consisting of two portions separated by a frangible barrier, one portion containing the emulsified thermal buffer in water and the other portion the salt that dissolves endothermically into solution. One specific version of the device is a container for transporting an amputated extremity such as a severed finger to another location for replantation.