The other night I wanted to melt some dark chocolate to cover some petzels with so I took out my Pyrex bowl (which I had used a few days earlier for melting some white chocolate) and heated 8 oz of Ghiradelli chocolate for 30 seconds. Took it out and stirred the chocolate - put back in for another 30-40 seconds. Bell dinged and when I opened the door it smelled burned. Took out the bowl and started to stir the chocolate to see if it was burned when suddenly the bowl popped - a chuck of the bowl below off the side (fortunately away from my hand and face) and the entire bowl cracked completely all the way around! Boy was I surprised - Pyrex splinters to so in addition to losing a nice mixing bowl I had to throw 8 oz of nice dark chocolate in the garbage 
I had baked cakes in my Pyrex bows before and had used them for heating chocolate in the microwave before so not sure if the lack of enough wet material in it caused the bowl to overheat so quickly or what. Anyway just wanted to pass this on in case some one else has the same idea. I am just glad it didn't explode in my face.....
Pyrex is known for their glass dishes exploding and sending glass shards everywhere! I stopped baking with them and only use pyrex containers to serve cool food in..sorry this happened to you. you are very lucky to not have been hurt!
I don't know how old your bowl is, but from what I've recently read, there's a problem with newer Pyrex exploding in ovens and such. Here's a website that has some info.
Scary. Pyrex used to be a name you could trust. I had a casserole dish crack in the oven. It didn't explode, but it was a mess. This was about 4 years ago before I heard all this other stuff.
http://hubpages.com/hub/Exploding-Pyrex
Whoa.........glad to hear that you're OK! That's a scary situation.
I've taken several chocolate classes and have been told to melt chocolate and candy melts in microwave safe PLASTIC bowls--fewer hot spots, so it's kinder to the chocolate when it comes to getting it to temper properly. Now I have another good reason to use the plastic!
Rae
I've had this happen doing the exact same thing. Mine didn't explode, but when I went to take the bowl out of the microwave it cracked all the way 'round and the bottom half full of melted chocolate was still in the oven while the upper portion came off in my hand.
Thanks for the info - I looked at that link which talks about the material that the bowls are made from. My bowl was 25 years old. I definitely will not try to do this ever again. Nor will I pour boiling water into my Pryex measuring cup!!! I am just still mad I lost two bars of chocolate 
Did you happen to set it on something cold or wet?
Set it on my granite countertop which could have been a bit cool but wasn't ice cold or anything drastic in temp change. I did notice when I had done this previously that the bowl got extremely hot during each melt cycle (much hotter than other glass bowls) so I guess maybe they just can't take the microwave too well.
wow, I've alwayss used pyrex in the micro or oven... dang... now what am I going to use in the oven to cook in?
seriously? not only do I do my baseballs in a pyrex bowl, my poor hubby is on a diet, and his chicken is baked in a pyrex dish daily. AND at least weekly I make greenbean wraps (wrapped in bacon, with my BBQ rub on them) or jalapeno's wrapped. and that takes well over an hour to get the bacon done..
I'm glad you are okay! I had one explode after I took it out of the oven and it embedded hot glass shard in the linoleum..Quote by @%username% on %date%
%body%