Should Cabinet Door Glass Be Tempered?

      A discussion of why tempered glass is preferable in some situations, and some information about tempering and about costs. September 27, 2009

Question
I am in the process of making some hutch cabinets with frameless glass doors. What kind of glass should I be using? The doors will be about 14" x 21" and mounted in those pin type glass door hinges with magnetic "push-in-pop-out" catches.

The guys at the glass shop said I should just go with regular 5mm glass with belt sanded edges. They said tempered glass is unnecessary. I insisted on polished edges which they have to send out for, but I didn't push them on the tempered part.

I haven't worked much with frameless glass before. Usually I use regular glass that goes in wood framed doors I have built. I have this nagging feeling that I should be using tempered glass for anything frameless like doors or shelves. I'm not so worried about the cost, just customer safety.

Forum Responses
(Cabinetmaking Forum)
From contributor G:
Tempered glass. Peace of mind, no callbacks. The glass supplier is just that - you have the liability.



From contributor A:
Our glass shop sells: regular glass, double strength, and tempered. We always use double strength for cabinet work. If it's possible that the pane may be kicked we will choose tempered. For shelves we use 1/4" float glass. Tempered is not necessary at that thickness.


From contributor T:
For peace of mind we have all glass tempered. It only costs us about 3 dollars more per piece of glass. 90% of everything we do is retail and it has to be tempered.


From contributor B:
Go with tempered. If there is any way glass can get broken, it will; it's just safer to use tempered.


From the original questioner:
Thanks very much for all the advice. I'll call the glass shop and ask them to temper the glass as well. I assume this is done through some kind of heat treatment after all the cutting and polishing is finished.


From contributor N:
Toughened "tempered "glass is made from annealed glass via a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace that heats it above its annealing point of about 720C. The glass is then rapidly cooled with forced air drafts while the inner portion remains free to flow for a short time. Tempered glass must be cut to size or pressed to shape before toughening and cannot be re-worked once toughened. Polishing the edges or drilling holes in the glass is carried out before the toughening process starts.


From the original questioner:
Thanks for the information on the tempering process. When I called the glass shop the guy actually tried to talk me out of it, saying that the glass was already cut and polished and, although it was possible, it would probably be $25/door to have it tempered. I didn't have much choice but to say go ahead. I think it's time to look for another glass shop who is more familiar with work like this.


From contributor J:
As one who owned a glass shop for several years, I can confirm several things for you: The description of glass tempering is right on. The shop is way overcharging you for the tempering. The absolutely best thing to do is temper glass when it will be used as a door - especially if at a height that is below the waist. If you don't use tempered glass and someone does get hurt you could very well be liable. Your instincts were right on - your glass supplier is doing you a disservice.


From contributor Y:
I disagree with some of the others. Using tempered glass will not remove any liability from you. The only thing to remove the liability is to not build it at all. That said, my preference would be annealed (non-tempered) 1/4", with a pencil polished edge. Tempered glass will give a slight distortion and is really unnecessary in this application, as you only have 2 sq. ft. in each door. The tempered will shatter just as quick as the annealed glass will crack and break. The exposed edge of a tempered piece is extremely vulnerable in this application and in my opinion the annealed would be as safe if not safer. Being a hutch, sounds like it might be above eye level, and the shattering glass may be more of a safety hazard than being cut by a piece of annealed. A shattered light showering down on top of your head would be very hazardous. I am assuming this is some sort of desk with a glass hutch above. Ultimately, I would have let the customer make that decision, sign off, then charge accordingly. If this was for my 12 year olds kid's room I would have used wood instead.


From contributor J:
Almost all local and national building codes specify tempered glass for entryways and other high traffic/high use areas. Using tempered glass will not remove liability (you are correct, nothing short of not doing the glass could do that), but it will protect one as a "prudent person" in following the guidelines and case law concerning this issue.

As an example, I make an entryway with glass sidelights and tempered glass. Someone later walks into the glass and damages his eye. I may indeed be sued, but my very strong defense is that I did "all that a prudent person could do" to make the entryway as safe as possible. On the other hand, I make a similar project with another type of glass and someone gets hurt. There is a real case that I did not do "all that a prudent person could do" to avoid that situation.

And no, the exposed edge is no more in danger than a side window of a car would be (same process). In fact, go to a junkyard and take a small adjustable wrench with you. Find a window and try to break that window by securing the wrench on an edge and twisting the wrench. Damn hard to do, trust me.

I am not an expert on tempered glass by any means, but I did deal an awful lot with this for 10 years when I had my art glass and entryway company in NC.



From the original questioner:
I appreciate all the input. This is great information for someone like me who is new to these variations in glass.

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