What is stealing the elixir of life?
November 11, 2017 5:56 AM   Subscribe

We make our coffee in a Pyrex jug with one of those plastic pour-over cones and paper filters. It tastes better than coffee from a fancy machine, but there's a problem. I always measure out a pint of water to boil, and usually get a pint of coffee back. But sometimes it's reduced to as little as 3/4 pint. I guess the rest of the water is absorbed in the coffee grounds, but why does it happen at some times and not others? How can I prevent it?
posted by Perodicticus potto to Food & Drink (9 answers total) 3 users marked this as a favorite
I would bet money that some days the water boils for longer on the stove. Evaporation is taking your coffee while it is still water.

My two suggestions: get an electric kettle. IF an electric kettle is not an option, set a timer for the boiling part of your process.
posted by bilabial at 6:00 AM on November 11, 2017

Sorry - I should have said, we do use an electric kettle. So it's not that.
posted by Perodicticus potto at 6:02 AM on November 11, 2017

Do you have changes in humidity? A dry room can absorb much more than on a humid day. I think, probably, maybe.;-)
posted by sammyo at 6:08 AM on November 11, 2017 [4 favorites]

I make coffee in an aeropress and I notice this sometimes. I've always thought it's got to do with the surface area of the grounds (i.e. do I str them? are they ground more finely?) more than anything else.
posted by jessamyn at 6:10 AM on November 11, 2017 [2 favorites]

Do you use the same variety, roast, and grind of coffee all the time or different ones? That would affect how much water the grounds absorb too.
posted by Small Dollar at 6:13 AM on November 11, 2017

I make coffee with a pour-over cone, too - CleverDripper - and use a digital scale to measure as I go. I just finished making two cups/pours and am still drinking one as I read this, so I went back and measured how much water the grounds and the filter absorbed for each. With an N=2, what I found was that for a 350ml pour with 16g of coffee and a #4 paper filter, I lost 45-47ml of water to the grounds and the filter, so about 13% of the water didn't make it into the cup. I dunked a fresh filter in water, wrung it out a little, and weighed that - the #4 filter ends up with about 8ml of water, so the bulk of the "lost water" went into the grounds. I'm going to speculate that the thing that is varying here is the amount of ground coffee you are putting in. If you are measuring by volume, there is for sure some variance (in weight) based on the coarseness of the grind.
posted by kovacs at 6:34 AM on November 11, 2017 [9 favorites]

Following on sammyo above, in dry vs humid weather the coffee grounds could also have absorbed some moisture before you pour the water through them. So, more water goes through and doesn't get absorbed. I don't think it's enough to account for your observations though. Pay attention to the humidity ...
posted by intermod at 6:39 AM on November 11, 2017 [1 favorite]

Are you pre-wetting your filter? The paper filter can retain a surprising amount of water. In my v60 this morning the filter retained 12g of water (out of a total 250g brew); Chemex filters can retain much more. Ymmv. It's also pretty variable day to day; filters aren't designed with amazing manufacturing integrity and quality control for consistency.

That's a huge swing in retention to grounds even from filters to filter, which is part of why most brew guides suggest pre-wetting the filter.

Kovacs' measurements are pretty typical for coffee retention of water, this fluctuates a little bit depending on grind size, humidity, and roast level, but not to the levels you're describing.

If this was happening to me (because this would totally drive me bananas) I'd be weighing every component in and out, just to find the culprit. You'll have the added bonus that weighing out your coffee:water ratio will improve your coffee game even further (for a pour over, a weight ratio of 1:16-17 is considered pretty ideal). You're already taking volumetric measurements and weight measurements are more reliable for brewing coffee. If you're also measuring your coffee volumetrically, that Could account for s wider swing in grounds retention. Coffee is like flour; it can be compacted and compressed easily within a volumetric measure; weight is far more reliable.

You don't need a fancy crazy scale. A $12-15 escali are perfectly acceptable and last forever.
posted by furnace.heart at 7:40 AM on November 11, 2017 [2 favorites]

Coffee is an agricultural product and roasting is art as much as science, which is all to say that beans that are labeled the same and presumably roasted the same can have markedly different abilities to absorb water and not let it go. So I'd also say that if you really want to know what's happening you should be weighing the dry coffee and the remainder after filtration. In my experience the "loss" which is just soaked up in the grounds varies quite a bit and it could very well account for your missing water.
posted by fedward at 6:50 PM on November 11, 2017

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