October 22, 2009, 13:54
Lindell V. RiddleHello Bruce,
I can tell you from personal and very bitter experience that unintended over-tightening of dial-feet can cause a hairline to develop. Another common preventable cause is carelessness in removing a dial, the slightest flexing of the dial causes a hairline, forcing it causes a really bad crack or chunks of porcelain to be dislodged. We also see chips and cracks at or radiating from the setting lever position due to the user allowing their lever to slam back against the dial.
On the multi-colored dials they often display multiple hairlines because of them being so brittle due to the dial being re-heated in an oven as each color or decoration was added. That is related to some hairlines caused by the expansion and contraction you mentioned brought on by the user going from intense cold into a heated room and visa-versa, something that happened in the normal course of events when these watches were in daily use.
Any shock such as dropping the watch as you mentioned also has consequences.
Perhaps others will come up with additional causes.
Be well my friend,
Lindell
