Abstract: The present invention provides reusable warmers of the supersaturated solution type that are substantially free of saddlebagging. The warmers also exhibit a more sustained period of time during which the heat pack remains within a therapeutically useful temperature range. The reusable warmers of the present invention also maintain a substantial degree of flexibility during their useful heat cycle. The reusable warmers comprise a flexible container, and located within said container, a supercooled salt solution, an activator for initiating crystallization of said supercooled salt solution, and a gelling agent, said gelling agent being present in sufficient quantity to convert said salt solution to a gel.

Abstract: The present invention provides reusable warmers of the supersaturated solution type that are substantially free of saddlebagging. The reusable warmers comprise a flexible container, and located within the container, a supercooled salt solution, an activator for initiating crystallization of the supercooled salt solution, and a gelling agent, the gelling agent being present in sufficient quantity to convert the salt solution to a gel.

Abstract: The invention is in a method of recharging or regenerating a substantially solid spent heat pack of the type in which a super-coolable salt solution is confined within a flexible plastic pouch and converted to solid form with evolution of heat, by contacting the solid contents of said pack with a source of microwave energy sufficient to melt the solid to the liquid state, without thereby damaging said heat pack.

Abstract: A highly reliable activator is provided for initiating the crystallization or destabilization of a super-cooled aqueous salt solution to cause generation of heat in a heat pack. The activator is characterized by a plurality of slits in a flexible metal article, with the opposing sides of the slits being in contact along at least a part of the length of the slit, and by an eroded and roughened surface on said article which comprises a number of minute metal nodules attached to and protruding from the surface, especially at or near the slit, which nodules are adapted to be detached or broken-off upon flexing of the activator. In addition the method of preparing said unique activator is provided which comprises tumbling said slit activators with an eroding material such as garnet powder to form the small nodules.