jaybar Senior Member Joined: 13 Sep 2011 Posts: 179 Location: Brooklyn Expertise: I love coffee
Posted Sun Sep 9, 2012, 7:33am Subject: Is there a formula to figure out beverage yield for a Chemex?
Try as I may, my beverage yield always falls short.
I thought the following formula would work:
Yield=water poured- water absorbed
I want to get to twenty ounces of beverage.
I figure the water absorbed to be 2* coffee weight,
I insert the filter, add the coffee, TARE the scale and pour the water. When I lift out the filter, I am left with far less that my supposed formula would show. Do I also need to account for the dry weight of the coffee and the weight of the filter?
I want to finnish with 20 ounces of beverage in the pot I am using the eight cup handblown. I can't use the bubble marker because that is at 24 ounces in the handblown.
What formula should I use? What amount of coffee and water will result in 20 ounces in the pot?
I think you're on the right track. A more accurate (but slightly more complicated) formula might be:
Beverage Yield = (Water poured)-(Water Evaporated)-(Water Absorbed by Grounds)+(Coffee Solids Extracted into Beverage)
Hopefully water evaporated is low, and as Steve says, you probably compensate for the instantaneous evaporation by pouring over a scale. Water absorbed by grounds might be higher than 2.0x for Chemex, we could call it 2.3x. Coffee solids extracted into beverage is ideally around 19% of the dry grounds weight.
So your typical pour using ounces by weight would be: 23 oz brew water; 1.42 oz dry grounds; 2.3x the dry grounds weight water absorbed; 19% extraction.
Beverage = (23 oz Brew Water) - (0 oz Water Evaporated) - (2.3x1.42=3.3 oz water absorbed) + (.19x1.42=.27 oz coffee solids) = 23 - 3.3 + .27 = approx 20 oz
That should be approximately correct, depending (mainly) on how much water is actually absorbed and evaporated, and (to a lesser extent) on how much solids material is extracted.
Posted Sun Sep 9, 2012, 7:48pm Subject: Re: Is there a formula to figure out beverage yield for a Chemex?
Ever the empiricist, I'd sacrifice a Chemex filter, weighing it, soaking it in water, letting it drain for roughly the length of a brewing cycle, and re-weighing it to determine how much water it holds. Who needs formulas when you can have actual hard data?
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