Ron wrote:
Chris Jarshant wrote:
All,

A few nights ago I had a good fire going with the
tempered glass doors closed on my pre-fabricated
fireplace. Well, I guess it got too hot, after an
hour or two, because one of the glass pieces shattered
into small cubes. No biggie, I had a replacement, but now I have
questions.

Questions:

1. The fireplace has tempered glass (it is a "Majestic BR42")
whose glass doors are able to withstand a documented gradual
rise to 550F.
Did my fire get that hot? I admit I loaded it with 4 or
5 small logs but it was not roaring by any means (I had
good embers at the bottom tho that were burning quite hot).

2. I'd like to not worry about the glass doors anymore.
My choices are a) get rid of them, b) never close them,
c) rebuild a *real* fireplace or woodstove, or d) get
better doors. I'd like to do d) for now. If I were to
replace the glass, should I simply get thicker tempered
glass? Or is there some other product that is the same
thickness (3/16" or 1/4" I don't know for sure) that has
extra heat protection?

3) Assuming a correct installation (the home builder installed
it so you never know, but assume for the moment). Using
standard wood for fuel, could I cause the fire to get so
hot that it catches something on fire inside the wall, like
some studs or drywall or insulation? Is it really that easy
for a residential fireplace to get so hot with traditional
fuel that it is a hazard to surrounding material used that
is "to code" in all respects?

Thanks for any insight!

I wouldn't worry about it.

Tempered glass can blow up for absolutely NO reason at all. You will
probably never have this problem again if you simply do nothing.

This may sound like a half-ass answer but it's the truth. I've been
holding a piece of tempered glass in my hand and had it blow up for NO
reason.

Ever heard of a doorglass blowing up in a car before for no reason?
Same thing.

I've seen back window glass blow up, under mild heat from sunlight or
even less reason. often there is an initiating flaw, like a nick, and
any mild stress from not being exactly conforming in curvature to the
opening, or not having enough expansion room will do it. Tempered glass
is less "liquid" than regular glass; it will handle a lot of stress
evenly distributed, any thermal stresses, but a tiny local stress riser
like a scratch or nick will quickly propagate into a big bang.

On the other hand, the windshield of my volvo has a serious curvature
error (you can feel it by hand) which I assume stresses it as it's
constrained into the correct shape, and I've been watching a crack
slowly propagate from the top to the bottom for the past 15 years. Just
about there.

Call any glass shop and they will tell you this.

BTW, I'm sure there is a scientific reason for it but a glassman isn't
a scientist : )