“Nose Method” of Calculating Critical Cooling Rates for Glass Formation

In the past, it has been shown that reasonably good estimates of critical cooling rates for glass formation could be obtained by computing the cooling curve which just passes through the nose of a T‐T‐T (time—temperature—transformation) diagram. Also, it has been noted that critical cooling rates found by this procedure are generally greater than those obtained by other methods. Herein, we provide an explanation of these observations. The nose method of computing critical cooling rates is compared with others, and specific illustrations are given for the glass‐forming systems SiO₂, GeO₂, and P₂O₅.