My Martini Glass is Stressed and Needs a Drink

Dear Tricia, This is a safety hazard question, so I wanted to ask the expert. I went back and read about exploding casserole dishes in the oven and blow torching "cold" glasses, but I'm still not sure. I want to use a martini glass to decorate a cake and use sugar/corn syrup mixture to make it look like there is a vodka/cranberry drink in the glass. And I am scared to put the hard ball sugar into the glass and breaking it. I like my eyes, granted they need a little work, but I would like to keep them working. So, will I cause the thin martini glass to shatter by pouring 325 degree melted sugar into it?

Great question, and thanks for referencing the blog I wrote about a gazillion years ago about breaking dishes in a hot oven. And also, I find it hilarious that you want to "ask the expert" about a safety hazard since I'm consistent about running into doors, dropping breakables and slamming my fingers in drawers. I'm a walking disaster and I have the bruises to prove it.
To digress for a second, and for those who don't want to go back and read the older stuff (you're missing out), I have to mention a day in culinary school when my partner and I were taking a blowtorch to a dessert served in a champagne glass. Since she was from the Virgin Islands, and I'm from Texas and neither or us carry the word "cold" in our vocabulary, we took the glass right out of the refrigerator and put the blowtorch to it. It immediately shattered. So, like dumbasses, we tried it again on another glass. Shatterific. Our teacher wasn't crazy about us. (And I wasn't crazy about her either, if I must say. So there.) The point is, you can't take a cold glass and immediately put something hot in it because there are little pockets of air inside the glass that expand when they get hot. When they expand too fast or too much, they explode and break the glass. And then you're left with a dessert served in broken glass while 20 fellow students look at you like you just farted.
So I understand your hesitation. Let me break down the science of it: when things get hot, they expand. My fingers swell in the summer time when its hot as hades outside. Carbon dioxide bubbles inside a cake expand in the oven and make the cake rise. And air pockets inside glass expand when you heat it. The problem is, glass is a terrible conductor of heat. You could pour hot sugar on half of a glass plate and the air pockets inside that side of the plate will start to expand, but the other side of the plate's little air pockets aren't doing anything because the heat is taking too long to travel over there. So with the inside of one part of the plate expanding and the other side doing nothing, there's a lot of "thermal stress" going on. (What a terrible term. How much stress can a dish go through? Get a job already.) And with all the "thermal stress," it breaks.
So how do we avoid that?
First, you need to make sure your martini glass isn't made from blown glass. Hand blown glass (shouldn't it be referred to as mouth-blown?) has much more irregular pockets of air than generic glass that is made from pouring molten glass into a mold. Not sure if yours is hand blown? I found the most comprehensive checklist here . If you're buying your martini glass at the Dollar Store, I don't think you have to worry about it being blown. Lucky you: functionality and its a bargain. But if you're buying a martini glass somewhere all posh-like such as Crate and Barrel or ZGallerie, try asking the people who work there. (That's how I found out my new glasses were blown, which explains why they all like to break in the dishwasher. Not awesome.)
Second, you need to ease the "thermal stress" the glass is going through... you know, like giving it a xanax. By slowly bringing the temperature of the glass closer to the temperature of the hot sugar, it puts less stress on the glass once you start adding liquid magma-like substances to it. While you're cooking your sugar, put the martini glass under the tap with running hot water and just let the water run. Don't just splash some warm water in it at the last minute: really let the glass get hot so that when you pick it up to dry it off, its super hot. This is going to help warm up the glass enough so that the temperature of the hot sugar isn't so shocking. When your sugar is almost ready, stop the water, dry off the glass, and its ready to pour the sugar in. And when you're finished pouring the sugar in, don't do something stupid like put it in the freezer. Mixing and matching temperatures is never a good idea.
I'm curious to see how your experiment turns out. Send pictures. Happy fake martini-creating! You should reward yourself with a real one after your dessert success.