California Color Guidance: Heat altered to yellow strain insulator CD 1131

By Colin Jung; posted November 10, 2015

View Original (2272 x 1704) 937KB


There are peach colored resin repairs to both ends of this California egg. Gene Hawkins, a mechanical design engineer by training, analyzed the fracture patterns in this insulator and concluded that the damage ends where the glass was sheared off were most likely caused by the strain of the guy wire in the wire groove at specific points. There are also fractures in the center of the strain (thickest part of the insulator) that Gene could not explain. The fractures are along two different planes and Gene could not find a mechanical reason why the fractures were there-- no impact points and no junk in the glass that might cause a shear plane. We both concluded that these particular fractures were probably caused by the heating of the insulator to change its color. Dwayne Anthony stated that the heating of a smoky purple California insulator would cause the glass to change color to this particular shade of yellow.

So the probable story is that a collector found a heavily damaged smoky purple California egg. Since it has no resale value, he/she decided to experiment with it and heat it up in an oven or kiln which resulted in the change in color and the additional fractures in the middle of the insulator. As the glass did not completely shatter, he/she decided to have it repaired.