Temperature‐Indicating Paints: Recent Advances Made in Germany in Developing Stable Paints for Use at High Temperatures

THE application of coalings of paint to parts of machine, such as bearings and other parts liable to become overheated from friction or some other cause, in order to indicate such temperature changes has been known, for some years. As long ago as 1919 Pinnock described (Jnl. Soc. Chem. Ind. Review, 1919, 38, 78) the use of the double salt‐mercury‐silver iodide, or mercury‐copper iodide, for this purpose, and reported that such preparations had been in use for ten years with satisfactory results. These, however, were only suitable for comparatively low temperatures, not exceeding about 100 deg. More recently the I.G. Farbenindustrie Akt. Ges. in their fuel research work at Oppau have found it desirable to undertake extensive investigation with a view to finding temperature‐indicating paints which could be applied under much more drastic and exacting conditions than those envisaged by earlier workers. A very interesting illustrated report of this work, with particular reference to air‐cooled aviation engines, has recently appeared in the V.D.I. Zeitchrift, “A.T.Z.,” and other German publications.