Last Updated: Nov 03, 2016 Views: 122
It may be either weathering or defects in the original glass which could cause it to become "frosted." I'm providing some links from our website which describe the process the glass goes through if it is weathered, as well as the crizzling process. If you need additional help with this, I can put you in touch with our glass conservation department. I am also providing a list of additional reading material.
http://www.sha.org/index.php/view/page/treatment#D (click on glass)