"arcoroc" mugs from France. Tempered glass, got them from goodwill years ago. About 3 months ago, I used one to store unpolished rocks from DS's kit.

Today, after rinsing with temperate water, DH sprinkled in some liquid dishwashing soap, rinsed, drained, & set it to the side on the counter.

Never hot or cold water used in this cup, today.

About 10 hours later, it shattered - loudly! I was upstairs & heard it. DH was about 7 feet away, & hadn't been closer recently.

Kept popping & crackling - with pieces of glass hopping - for more than 20 minutes! ("Snap-crackle-hop", lol).

We just stood... Staring, listening, watching & theorizing. I asked, "you don't think it's supernatural, do you?" & he said "no way, there's a logical explanation". Then he reached out to pick up a piece of glass, jerked back and dropped it - said it "shocked me - like, electrically!". He's thinking somehow, after 15 minutes, some kind of vibrations made it feel shocking...

I took this pic, placed another mug behind for reference of what the rubble used to look like...

Any thoughts? We are stumped, I've googled & all I find is temperature issues. I also posted it in Collectibles forum, thinking perhaps someone familiar with glassware can explain it.. Help?

Stress is created in the glass from uneven (or too quick) cooling. Proper annealing results in an object with minimal internal stress. When a properly annealed object breaks, the result is usually larger jagged pieces.

Tempered glass uses a very different process - in this case the glass is brought down in temperature very quickly, with the intention of creating an internally highly-stressed object. Contrary to what you'd think, this internal stress can make the object much stronger, however any scratch or chip can spread throughout the object in an 'explosive' fashion.

The result of a piece of tempered glass breaking is a billion little shards.

Note that as with most things glass, there is an 'art' to tempering - its not an exact science. Its entirely possible that one of the ovens at the factory was + or - some degrees or the glass formula that day was a little different and the result was your mug is not an strong as others made on the same production line.

I've linked the Wikipedia article on Rupert's drops, which are a great illustration of the potential explosiveness of tempered glass.

Flat sheets are created by heating and then cooling it rapidly.

It causes the fracturing into 'crumbs' (small pieces that are not large enough to fall and cut) when a scratch penetrates through temper layer and causes the stress to be released.

Once the crumbling starts it will not stop until nearly all the internal stress is relieved.
For windows the entire pane shatters, normally very quickly.
It can even make a loud sound similar to a basketball or soccer ball hitting the window.

Tempered glass was used in every car window except the windshield for many years.
It avoids having large sharp pieces of glass near people from an accident.
Windshields are 'safety' glass made by laminating plastic between layers of glass. They hold the piece together if the glass breaks, and the plastic prevent objects fr entering (or leaving) the passenger compartment.

I would bet Casey is correct.
A small nick (one you might not be able to easily see) probably got thing started.

Energy_rater, lol - I may (do!) have a couple holes in my siding from arrows, but nothing inside the house from anything. :-) That's 1 of 2 holes, from something before our time here, towel bar or such.

Have an explanation for the "shock" he felt, btw. I asked him "Hey, was that your left hand you used to pick up the glass piece?". He had a forehead-thumping moment & a chuckle at himself. Years ago, he cut his hand open - surgery reattached what nerves, tendons, muscle, etc, that they could, but he'll never have feeling in part of a few fingers. More to the point - occasionally any random thing can touch something "just right", & he never knows what different bizarre sensation he'll feel. We decided a sharp point must've touched a malfunctioning nerve, which felt like an electrical shock going up to his elbow.

So, all aspects of mystery are resolved. Thank you all for your patience & advice on such an off-topic question!

FTR, I was teasing DH - about supernatural (ghostie) causes... Forgot he'd seen one in junior high. In his bedroom, for about 5 minutes - till she walked back to the other side of the room & gave him a clear path to the door. Which he took, at a run. (Lucky guy - I've never seen one!).

let's hear it

And that "falling house" thing? That was just added to the documentary film, for drama. As you can see, I'm still here. :-D

As for the arrows... Actually, Ted Nugent lives next door, & REALLY hates loud music. That damn yankee really gets to storm-trooping at 1:00 am if my Neil Diamond cd volume gets cranked up. Arrow #2 was during Barry Manilow - so it wasn't just because he thought Neil Diamond was cheesy, he clearly just doesn't like loud music in general.

The removable sections are nice thick tempered glass, and even come with cloth bags to store them.

He bumped an edge trying to slide it into the cloth bag on the edge of the rear deck.
The 'explosion' scared him pretty well as the piece turned to glass 'crumbs' in his hands.

There is a LOT of stress built up in tempered glass (on purpose).