What if there were no spoon, Neo?

August 19, 2015 10:07 AM

I sometimes make iced coffee by placing a glass mason jar filled with ice into my single serve coffee maker and letting it brew / fill with hot coffee. I include a metal spoon inside the jar to act as a kind of heat sink and prevent the glass from breaking due to thermal stress. But should I bother? Does that spoon actually do anything?
posted by zarq to Food & Drink (8 answers total)

I don't think heat will transfer to the spoon fast enough to make a difference. The ice is more than capable of reducing temperature quickly, I think.
posted by and they trembled before her fury at 10:09 AM on August 19, 2015

Pretty much anecdotal but I do the same thing with my aeropress and a mason jar. The mason jar is pretty resistant to thermal shock, and if your coffee is coming out above 180F you're lucky, so I don't think you need to worry about the spoon.
posted by werkzeuger at 10:12 AM on August 19, 2015

Mason jars are designed to handle pretty extreme ranges of temps. Make sure the hot liquid is hitting the ice not the glass first, a spoon might help with that. I'd make it the other way round by adding ice to the hot coffee if that is a concern. Not a scientist but I home can a lot.
posted by wwax at 10:13 AM on August 19, 2015

Unless I missed a decimal place, heating a 20 gram steel spoon from 30 C (room temp) to 80 C (hot coffee) takes the same amount of energy out of the hot coffee as melting 1.5 gram of the ice (about 500 J). So I would say it's having a negligible effect compared to the ice.
posted by ftm at 10:24 AM on August 19, 2015

heating a 20 gram steel spoon from 30 C (room temp) to 80 C (hot coffee) takes the same amount of energy out of the hot coffee as melting 1.5 gram of the ice.

Just to for comparison, a cube of ice 1/2" on a side would be approximately 1.9 grams, and one average-sized ice cube (about 1.5" x 0.75" x 0.75") would be about 13 grams.
posted by Johnny Assay at 11:22 AM on August 19, 2015

what wwax said - few of us use mason jars for their intended purpose of home canning, but that's typically a process that puts a LOT of pressure on the glass - I don't think you need to worry.
posted by randomkeystrike at 12:56 PM on August 19, 2015

Pour the hot coffee slowly over the back of the spoon, it will take some of the heat and melt the ice less, so your coffee will be less watery.
posted by vrakatar at 4:09 PM on August 19, 2015

I make iced coffee in a regular pitcher filled with ice and the pitcher is still fine. I've started to worry about cracking the thing and so now I pour cold milk into the pitcher before adding the coffee.
posted by any portmanteau in a storm at 7:48 PM on August 19, 2015