# Where does my coffee go? **URL:** \ **Category:** Factual Questions\ **Created:** [June 5, 2013, 4:29pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219 "2013-06-05T16:29:44Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![jsc1953](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@jsc1953](https://boards.straightdope.com/u/jsc1953)\ **Post date:** [June 5, 2013, 4:29pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/1 "2013-06-05T16:29:44Z")
My drip coffee maker has started making my coffee disappear. I pour in 12 “cups” (using the bogus coffee definition of a “cup”) of water each night, add ground coffee to the cone-shaped filter. In the morning I get back about 8 cups of coffee. I ran an experiment last night, and used the same amount of water (and a filter) but no coffee, and got 11.5 cups of hot water. So apparently the coffee grounds are absorbing the water, not surprisingly. But the missing water weighs about 1 lb, and my filter of coffee grounds weighs an ounce or 2, max. So where’s my coffee? ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [June 5, 2013, 4:32pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/2 "2013-06-05T16:32:48Z")
Do you have the pre-charged type where thier is always a full tank of hot water? If this is the case I would think a seal is bad somewhere allowing for vapors to escape instead of condensing and running back into the tank. ---
**Author:** ![Whitney\_Harper](https://avatars.discourse-cdn.com/v4/letter/w/f0a364/32.png) [@Whitney\_Harper](https://boards.straightdope.com/u/Whitney_Harper)\ **Post date:** [June 5, 2013, 4:35pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/3 "2013-06-05T16:35:12Z")
I’m not sure, but it could be steam, which coffee makers emit usually when it is finishing making the coffee. ---
**Author:** ![kayT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayt/32/3633_2.png) [@kayT](https://boards.straightdope.com/u/kayT)\ **Post date:** [June 5, 2013, 4:35pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/4 "2013-06-05T16:35:28Z")
gallon of water = 8.33 lbs 16 cups in a gallon a coffee cup “cup” is really about 1/2 cup on my coffeemaker So you lost 1/2 of a coffee cup, so you did not lose a pound of water! Maybe 1/8 of a pound. I bet the grounds absorbed that much, and some evaporated as steam too. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [June 5, 2013, 4:38pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/5 "2013-06-05T16:38:36Z")
actually measure the weight of the substances. report back. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [June 5, 2013, 4:40pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/6 "2013-06-05T16:40:01Z")
Coffee gives you energy. The missing mass has been converted to energy. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [June 5, 2013, 4:40pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/7 "2013-06-05T16:40:05Z")
Steam and grounds absorption are the usual places. Most makers completely empty the tank, but may boil off the last few ounces ineffectually. (Side-tank types use the boiling steam pressure to push the hot water up and through the mechanism; at a certain point this fails and the last bit of water just boils away.) I fill mine to the very brim of the water tank, probably a cup past the 10 mark, to get a full carafe. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [June 5, 2013, 4:44pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/8 "2013-06-05T16:44:17Z")
> [@Colophon](#): > > Coffee gives you energy. The missing mass has been converted to energy. In addition, the OP is setting up the coffee maker the night before (it is dark). In the morning it is light, and that light needs energy for its creation. All told, he’s lucky to get _any_ coffee. ---
**Author:** ![Muffin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muffin/32/4341_2.png) [@Muffin](https://boards.straightdope.com/u/Muffin)\ **Post date:** [June 5, 2013, 4:44pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/9 "2013-06-05T16:44:19Z")
If you come upon a hallucinating rat twitching it’s way across the counter, you have your answer. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [June 5, 2013, 4:49pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/10 "2013-06-05T16:49:00Z")
> [@kayaker](#): > > In addition, the OP is setting up the coffee maker the night before (it is dark). In the morning it is light, and that light needs energy for its creation. All told, he’s lucky to get _any_ coffee. Also, coffee is a diuretic, so it causes the pot to lose fluid at a high rate. ---
**Author:** ![jsc1953](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@jsc1953](https://boards.straightdope.com/u/jsc1953)\ **Post date:** [June 5, 2013, 5:15pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/11 "2013-06-05T17:15:24Z")
> [@kayT](#): > > gallon of water = 8.33 lbs > 16 cups in a gallon > a coffee cup “cup” is really about 1/2 cup on my coffeemaker > > So you lost 1/2 of a coffee cup, so you did not lose a pound of water! Maybe 1/8 of a pound. I bet the grounds absorbed that much, and some evaporated as steam too. I lost 4 “cups” when there’s coffee in the filter. The 1/2 cup loss was my experiment with no coffee. 4 coffee “cups” = 2 real cups = 1 pt = 1 lb (“a pint’s a pound the whole world 'round”) ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [June 5, 2013, 5:20pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/12 "2013-06-05T17:20:10Z")
[del]A cup of coffee officially is 6 oz. That’s probably what the coffeemaker is measuring it as.[/del] As soon as I posted this, I found other equally reliable sources claiming 5 oz. as the standard. ---
**Author:** ![jsc1953](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@jsc1953](https://boards.straightdope.com/u/jsc1953)\ **Post date:** [June 5, 2013, 5:24pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/13 "2013-06-05T17:24:41Z")
> [@Amateur\_Barbarian](#): > > Steam and grounds absorption are the usual places. Most makers completely empty the tank, but may boil off the last few ounces ineffectually. (Side-tank types use the boiling steam pressure to push the hot water up and through the mechanism; at a certain point this fails and the last bit of water just boils away.) > > I fill mine to the very brim of the water tank, probably a cup past the 10 mark, to get a full carafe. Interesting…I wonder if mine is failing prematurely, and excess boiling is happening? ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [June 5, 2013, 5:30pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/14 "2013-06-05T17:30:24Z")
You shouldn’t lose water unless the pot is preheating the water over night. We have that problem with our commercial [Bunn coffee maker](http://www.amgears.com/coffee-makers/bunn_im300/bunn-coffee-maker-04275-0031-VPS.gif) at work. Every Monday some of the hot water in the reservoir has boiled off over the weekend. We always run a pitcher of water through first before trying to make coffee. Otherwise you only get a half pot of coffee for a pitcher of water. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [June 5, 2013, 6:59pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/15 "2013-06-05T18:59:30Z")
We have a coffee maker with a built-in grinder. We lose no more than half a cup or so. The tank and the pot both have markings - and there is no fudge factor since if you fill the pot to 12 cups and put it in the tank you get 12 cups of water in the tank. Perhaps pre-ground coffee absorbs more? We’ve also had leaks or runovers during brewing - look under the coffee maker for puddles. Do you still get a loss if you fill it and brew immediately? ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [June 5, 2013, 7:04pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/16 "2013-06-05T19:04:37Z")
Poltergeists are notorious coffee addicts. That’s how they stay up at night to pull pranks. ---
**Author:** ![Kiwi\_Fruit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kiwi_fruit/32/12_2.png) [@Kiwi\_Fruit](https://boards.straightdope.com/u/Kiwi_Fruit)\ **Post date:** [June 5, 2013, 8:49pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/17 "2013-06-05T20:49:07Z")
> [@jsc1953](#): > > I lost 4 “cups” when there’s coffee in the filter. The 1/2 cup loss was my experiment with no coffee. > > 4 coffee “cups” = 2 real cups = 1 pt = 1 lb (“a pint’s a pound the whole world 'round”) You know that it’s not, do you? 1 imperial pint equals 20 fl oz = 19.98 oz (approx), so a pint’s a pound in the US only! > [@](#): > > A pint of pure water weighs a pound and a quarter. ---
**Author:** ![jsc1953](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@jsc1953](https://boards.straightdope.com/u/jsc1953)\ **Post date:** [June 6, 2013, 3:24pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/18 "2013-06-06T15:24:58Z")
Mystery (largely) solved. Last night I filled the reservoir with 12 “cups” of water. And for good measure, I weighed the filter and ground coffee: 1.2 oz. This morning, I peeked into the reservoir before it started dripping, and was surprised to see that the water level had dropped below the 10 cup mark. So it’s evaporating overnight. Why it’s started to do this recently, I do not know – change in humidity maybe? And just for completeness, the weight of the used coffee grounds + filter was 3.2 oz. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [June 6, 2013, 4:44pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/19 "2013-06-06T16:44:07Z")
That seems like a lot of evaporation to me. Isn’t there a cover over the water? Even without a cover, that still seems like a lot. Is the water heated all night? Are you sure there isn’t a puddle under the coffee maker? ---
**Author:** ![jsc1953](https://avatars.discourse-cdn.com/v4/letter/j/5daacb/32.png) [@jsc1953](https://boards.straightdope.com/u/jsc1953)\ **Post date:** [June 6, 2013, 5:00pm UTC](https://boards.straightdope.com/t/where-does-my-coffee-go/660219/20 "2013-06-06T17:00:04Z")
> [@ZenBeam](#): > > That seems like a lot of evaporation to me. Isn’t there a cover over the water? Even without a cover, that still seems like a lot. Is the water heated all night? Are you sure there isn’t a puddle under the coffee maker? Yes. No. Yes. [Next page](https://boards.straightdope.com/t/where-does-my-coffee-go/660219.md?page=2)