The Bag Goes Crunch

I stopped by the wine store on my ride home yesterday to stockpile some cheap bottle for our wine rack. I've discovered that when empty my messenger bag can handle exactly six bottles and it's packed full. If I go one over and hit a bump on my ride home I'll end up picking broken glass off the concrete while cars scream past. When putting in the sixth bottle yesterday, I heard the sickening crunch you sometimes hear when packing a piece of luggage. It wasn't a bottle, but something else I'd forgotten about in the bottom of the bag. The damage was done, and there was no need to dig out the wine in the checkout line and find it. When I arrived home I sorted the bag and found my sunglasses in the bottom, somehow in one piece with no visible damage. I'm not sure what could have caused that crunch, but I imagine I'll find out when my sunglasses disintegrate off my face the next time I wear them.