When the need arises for measuring temperature in various industrial situations, most engineers think in terms of expensive electronic temperature measuring equipment. In many cases, though, you can do the job with less costly and much simpler methods. When the need is only for an indication that a pre determined temperature has or has not been reached, heat-sensitive materials in the form of crayons, paints, pellets, or labels can do the job readily, inexpensively, and accurately enough for most industrial applications.hese heat-sensitive, fusible materials consist of crystalline solids. When heated, a temperature will be reached in which the solids change sharply to a liquid. The melting point is reproducible and is virtually unaffected by ambient conditions that may cause errors with other temperature-sensing methods. For example, electrical means of measuring temperatures often function erratically in the presence of static electricity, electrical "noise" or ionized air near electrical equipment.