GB1450381A - Temperature indicator - Google Patents

Abstract

1450381 Temperature indicators J E HUGHES 28 Sept 1973 [28 June 1972] 30208/72 Heading G1D A temperature indicator which gives an irreversible indication when the temperature of an article, e.g. foodstuff, has exceeded a predetermined temperature, comprises a rigid tubular capsule which is divided into two compartments 24a, 24b by a partition 26, one compartment 24a containing a non acidic aqueous solvent whilst the other 24b contains a dye which is soluble in the solvent. The partition ruptures on freezing of the solvent allowing subsequent melting to react with the dye to produce a colour change. As described, the dye may be of the type which is colourless or white when solid and coloured when dissolved in the solvent. Alternatively, the solid dye may be enclosed in a covering of white or colourless material e.g. sugar which dissolves in the solvent so as to allow the dye to be released. Solid dye portions may be enclosed in materials which dissolve in the solvent at differing rates. Suitable choices of dyes will thus enable the time lapse after melting of the solvent to be ascertained. The solvent may be an ethyl alcohol in water mixture. An end cap 16 may be of transparent plastics and shaped to give a magnified image of the contents in compartment 24b.