jaybar Senior Member Joined: 13 Sep 2011 Posts: 107 Location: Brooklyn Expertise: Just starting
Posted Sun Sep 9, 2012, 8:33am 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?
Posted Sun Sep 9, 2012, 6:21pm Subject: Re: Is there a formula to figure out beverage yield for a Chemex?
For the Chemex, the "2" factor may not be correct.
You also have an additional error because the tare includes the mass of the coffee (and the mass of the filter), which you remove at the end.
Say the chemex weighs 30oz
If you add 1.5 oz of coffee (we'll neglect the filter weight), then tare the whole deal, then add 25.5oz of water, then remove the grounds, you have this situation:
30 + 1.5 = 31.5 oz tare to zero.
+25.5 oz water, then remove the grounds, you're probably recording about 21oz of coffee.
Your actual produced coffee is really 22.5, or the weight of the coffee more - because the coffee was included in the tare but removed to determine produced coffee.
You can also check this out by getting the measurement, then just re-tare with another vessel, and check the yield - you'll find the missing weight of coffee, I'm sure.
The general equation is P = produced coffee (you call it yield) W = Brew Water Mass C = Brew Coffee Mass (the dry ground coffee you start with) A = Absorption coefficient (you're estimating around 2)
P = W - (A C)
In this case
P = 25.5 - (2 * 1.5) = 22.5 oz
That's IF the absorption is 2.
The wet spent grounds mass, G = C (A + 1) = 1.5 * (2+1) = 4.5oz
If you recorded all the steps: Chemex = 30oz Coffee = 1.5oz Water = 25.5 oz
Grounds = 4.5 Produced coffee = 22.5 Chemex = 30 oz.
But your reference (tare) included an offset of 1.5oz - so the produced coffee is off by the weight of the brew coffee.
Don't forget you may lose up to an oz of brew water due to evaporation, depending on relative humidity and how long you pour, but if you're looking at the brew water weight at the end of brewing, this should be well-accounted for.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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, 8:15pm Subject: Re: Is there a formula to figure out beverage yield for a Chemex?
It occurs to me that Chemex filters are big, thick things that probably absorb more water than most other filters do. Maybe that's where part of your yield loss is going.
Posted Sun Sep 9, 2012, 8:48pm 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?
Posted Mon Sep 10, 2012, 3:15pm Subject: Re: Is there a formula to figure out beverage yield for a Chemex?
GVDub Said:
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?
Why not just run an empty (coffee-less) brew cycle?
For the OP: I ran this just this morning with the CCD set up as a pourover.
If I tare the CCD on the mug with a filter and coffee, then pourover until I get to my normal 425g of brew water, then pull the coffee and filter out of the CCD - I get my expected yield (in my case, the CCD with filter has A = 2.3) MINUS the coffee mass. (About 365g of coffee, but only measures 340g).
Furthermore, if I take everything off, re-zero the scale, and reweigh my mug (which I know is 526.5g) I get a total mass of 891.8g, or a yield of around 365g.
Recall the simple model: P = W - (A C)
W = 425 C = 25 A = 2.3
P = 425 - (2.3*25) = 367.5g predicted.
No need to worry about strength, extraction, etc. Coffee is just a recipe, and this is just a simple way of estimating the yield of the recipe.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Mon Sep 10, 2012, 6:20pm Subject: Re: Is there a formula to figure out beverage yield for a Chemex?
Oh, and before too many ask, the strength was 1.30%TDS for the previous example.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Symbols: = New Posts since your last visit = No New Posts since last visit = Newest post
Forum Rules: No profanity, illegal acts or personal attacks will be tolerated in these discussion boards. No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum. No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum. Who Can Read The Forum? Anyone can read posts in these discussion boards. Who Can Post New Topics? Any registered CoffeeGeek member can post new topics. Who Can Post Replies? Any registered CoffeeGeek member can post replies. Can Photos be posted? Anyone can post photos in their new topics or replies. Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts. Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.
= No New Posts since last visit 