the coolant can be any suitable coolant known in the art including but not limited to ice gelatinized ice or chemical coolants in the preferred embodiment the chemical coolant known as the u201c thermal media pack u201d available from mid lands chemical co of omaha nebr is used preferably the coolant is placed in the bottom of container 1 and underneath specimen however coolant 28 can also be placed above or to the side of the specimen in addition depending on the rate and degree of cooling desired more than one coolant can be placed in the container in any combination of the positions mentioned herein for example two coolants below the specimen or one above and one below the specimen to control the rate at which coolant 28 cools the specimen another competing heat source 40 is placed within the container 1 with the specimen and coolant 28 for example the competing heat source can be a thermally active material such as expanded polystyrene in the preferred embodiment shown in fig1 4 the competing heat source comprises expanded polystyrene panels 45 placed in container 1 adjacent the inner surface of the vacuum insulation panels 30 in bottom wall 15 and side walls 20 the amount of expanded polystyrene within the container 1 will affect the rate at which the coolant 28 cools the specimen the more expanded polystyrene within the container u2014 in other words the larger the competing heat source u2014 the slower the cooling rate conversely if less expanded polystyrene is placed.