Spiral Cracks in Glass Tubing

Abstract

To the examples cited by Dr. J. J. Hopfield and Messrs. B. N. Clack and N. L. Harris on this subject, I should like to add a further rather unusual example. This was in X8 soda-glass tubing of 6–7 mm. diameter and 0.15–0.25 mm. wall-thickness. Large quantities of this tubing were being handled, and frequently, when it was being cut into lengths, a spiral or rather helical crack would fly along the piece. The cracks were of 5–7 mm. pitch, and produced springy lengths of up to 12 in.