Thursday, September 07, 2006

The reason why we don't melt butter and cocoa in the microwave (anymore)





14 Comments:

Publius said...

holy shit!

BernieRA said...

I was going to comment, but publius took mine!

kermitthefrog said...

Wait, in case I'm getting this wrong from the photo, it looks like your microwave just sawed the top your glass off.

Yeah, what P. said.

wolfa said...

Melt butter and cocoa, like the powder?

Lucy said...

that's so cool!

turtlebella said...

weeeird, I didn't know a microwave could DO that...holy shit, indeed.

Miss M. said...

I'll second/third/fourth/fifth the holy shit's. And add a stunned "wow" and suggest investment in a double boiler for future such ventures.

Quite impressive really.

grace said...

You know there's a name for this? It's called thermal shock. It's caused by rapid and unequal change in temperature in the vessel. You can perform the same trick by putting a glass in the freezer for a bit, and then running hot water into it. Pyrex I think is more resilient, but (if my experience is anything to go by) it shatters more readily if you drop it.

StyleyGeek said...

I think the moral of the story is that grace is smarter than all of us :)

I wondered if it was something like that, but I would have thought it would shatter the glass, rather than split it into two solid pieces (with a very smooth edge along the split, too).

Queen of West Procrastination said...

I'm going to have to show that picture to my husband. He's going to love it. And then I'll have to prevent him from trying to replicate the reaction in our own microwave.

Anonymous said...

The microwave isn't the essential bit - the thermal shock is - having poured refridgerated milk into a glass, wandered into the lounge, and had the base of the glass fall off. Nice clean break like yours too.

Stellar_muddle

Weekend_Viking said...

Tempered glassware is bad, ok? Arcoroc is the main producer of such stuff, but about the only tempered glassware I will trust is Pyrex. Arcoroc drinking glasses are particularly bad, and prone to shattering under thermal shock or if their surface becomes abraded or scratched (In tempered glassware, surface scratches and cuts break the tempered outer surface and become a stress focal point, so even very slight shocks, either thermal or impact, can lead to it shattering.)

Ceramics are much less prone to this sort of thing.

(As an aside, the first production of tempered glassware was a late medieval arab development, as if you got the temper right, a glass pot full of gunpowder would explode in such a way as to shatter the pot into hundreds of square glass grenade fragments.)

grace said...

That's very interesting, Weekend Viking [and don't think I don't know who you are ;-) ], about the tempered part only being a layer on the outside. So a perfect new Pyrex is great, but a slightly-scratched older one is prone to self-destruct if not handled gently! I wondered why this stuff seemed so fragile.

Ceramics are prone to thermal shock also, but this varies a lot, depending on the type of clay, the strength of construction, the firing temperature, and the type of glaze used.

To take a tangent...when we did ceramics at design school we were reminded that a ceramic object can be broken, but the pieces themselves are virtually indestructable (this is why pot sherds provide such a wealth of archaeological information).

Weekend_Viking said...

There are photographic filter techniques under various light wavelengths you can use to get an image of the stress patterns in glass and metalware. (Ask an engineer. They also have very scarey modelling software that can model them, too.) Basically, corners, edges, angles will be locations of stress points that may be the locus for thermal shock fracture. Round is good.

Grace, I use a lot of ceramics doing various blacksmithing and metalcasting things, usually as crucibles, but also for casting moulds, quenching clags, fluxes, etc, and have had some exciting thermal shock experiences from them, too.

However, I've never had a ceramic eating/drinking vessel do the same sort of exciting 'splody thing in every day use (not counting the obvious like taking out of oven and placing in water, etc, which will thermal shock most things.) The Arcoroc glasses at College House used to explode if you looked at them in a funny way, too. I think the problem is a much lower temperature threshold for thermal shock in the tempered glassware, especially if worn with surface dislocations/imperfections.

Cheers

(I may have experimented with ways of encouraging Arcoroc glasses to explode. Just a bit. Slightly.)