Abstract: A reversible disposable thermometer usable as a safe, convenient and low cost replacement for the mercury in glass clinical thermometer, comprises temperature indicating materials, with controllable and precise melting points, embedded in a flat probe, wherein they are arranged into an indicating matrix, located on both sides of the probe, which covers the physiological temperature range of humans in 0.2.degree. F. steps, and supplemented by a means of affecting the crystallization process of the compounds so that the melting process is accurately definable and the difference between melted and unmelted stage is readily discernible, such means preferably comprising cationic dye seeding in the materials to multiply crystal nucleation sites for fineness of crystal structure and to provide light scattering properties and, further to reduce solidification induction time to make the thermometer reversible and reusable.

Abstract: Food temperature vessel or other utensil comprising a thermochromic layer at a surface thereof indicating temperature of the food content of the vessel within a safe range above 60.degree. and below 70.degree. C. corresponding to achievement of safety conditions by raising the food content above the minimum temperature of the range to produce reversible protein denaturation in certain microorganisms to limit sporulation, and below a limit corresponding to irreversible protein denaturation and tissue injury of the tongue, lips or throat tissues of the user on the upper end of the range. The thermochromic layer goes through a transition from red to black across the range.