Question regarding glass block lights

Notice several posts on here regarding the glass block lights decorated for Christmas. I'm hoping to get some questions answered from someone who is an expert. I made two of these, one for myself and one for my mother. We both had them for about a week and all of a sudden we both heard a loud noise and they had cracked into (a day apart from each other). Trying to figure out what could have caused this. Husband had drill them for me slowly per instructions I found on the web. Didn't crack at time of drilling, but a week later after sitting lighted up. Any ideas would be appreciated. Please email me at billyboy12b@yahoo.com. Thanks, Page

First off, what type of drill bit was used to make the hole? A regular drill bit, or a spear shaped (Triangular glass bit) makes a frayed, flaked, and/or fish-eyed hole (not smooth). A professional barrel type diamond bit makes a smooth hole. A frayed hole responds badly to temperature change, eg., lights on, lights off. Temperature change causes a flake to become a crack. Next time, try a barrel type diamond dust bit or have a glass shop do it for you.



The above is advice from my DH who is a professional glazier. We hope we've helped. [img]images/smiley_icons/smile.gif[/img]