Espresso volume and weight aren't jiving- I don't think?

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Vindibona1
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#1: Post by Vindibona1 »

I'm perplexed. I've been weighing out my beans on a jewelry scale that supposedly measures to 0.01 grams. Until now I have seen no reason too doubt its accuracy. To check I have another scale that only measures 0.1 grams, so I thought accurate enough to double check in the ballpark. 16.5 grams of ground beans on the jewelry scale looks like 15g on the other one. Close enough, I thought. The jewelry scale always seemed to be quite accurate as it meshes up with the weight of drone accessories that I need to know for FAA purposes.

I recently got one of those glass cups with the markings (rattleware) and measured water in it to see that the markings were accurate and I have no reason to doubt them. But here's the problem... I pull my shots of espresso, with the marked glass only, stop at 2oz/60ml. Then I measure the shot on the scale, having zeroed with the empty glass cup... and I'm reading 55gm, thinking that I had 2oz/60ml of liquid.

I have to be missing something. How can 2oz of coffee be 55gm? I also measured liquid retention in the puck/portafilter after brewing and 16.5 grams of coffee in a 500g portafilter retains about 19gm of water, if that helps.

Am I doing something wrong, or is it the scale or possibly the marked clear espresso glass?

Satchmo780
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#2: Post by Satchmo780 »

Do you count the crema? It's mostly foam, not liquid.
LMWDP #737

Abecker
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#3: Post by Abecker »

I could be wrong but I believe this is the exact reason its better to use a scale vs volume. Espresso has a different density than water and also has crema. Therefore you wouldn't be able to assume that 60ml of espresso should weigh 60 grams in the same way that 60ml of water weighs 60 grams.

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Jeff
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#4: Post by Jeff »

Those marked glasses are probably only accurate to 5-10%

That espresso isn't pure water is also an effect. It can often be in the 8-15% range of dissolved solids, by weight. I've never looked into the density of espresso.

Calibration weights are not very expensive in this range, maybe US$10 or less. Check your scale's calibration method as most require a specific weight. "Class M1" or "Class M2" are reasonable. I'd avoid anything that didn't specify the grade, as ones with claimed accuracy generally aren't much more in this weight range.

One reference for tolerances is https://weighing.andonline.com/sites/de ... ates_1.pdf

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Randy G.
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#5: Post by Randy G. »

"How many minutes does three inches weigh?" I loved the look on elementary students' faces when I asked them questions like that.
Mixing volume measurements and weight measurements is going to remain confusing. The 1:2 espresso ratio so often mentioned is based on weight. 20 grams of coffee in makes 40 grams in the cup. Of course, that is a good starting point but not a rule. But trying to measure volume of espresso to quantify an extraction is like then other imponderable I would pose to a student asking too many questions:
My Q: Did you bring your lunch today or did you ride the bus?
Response: I eat in the cafeteria.
My A: Well, then how did you get here?!
EspressoMyEspresso.com - 2000-2023 - a good run, its time is done

Vindibona1 (original poster)
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#6: Post by Vindibona1 (original poster) »

Jeff wrote:Those marked glasses are probably only accurate to 5-10%

That espresso isn't pure water is also an effect. It can often be in the 8-15% range of dissolved solids, by weight. I've never looked into the density of espresso.

Calibration weights are not very expensive in this range, maybe US$10 or less. Check your scale's calibration method as most require a specific weight. "Class M1" or "Class M2" are reasonable. I'd avoid anything that didn't specify the grade, as ones with claimed accuracy generally aren't much more in this weight range.

One reference for tolerances is https://weighing.andonline.com/sites/de ... ates_1.pdf
I'm glad I'm not totally nuts and that my scale is correct. So I guess I have to forget volume almost entirely and go with weight, which I'd been doing until last week when I got an espresso clear glass with the ounce and ml markings. What good is it to have a marked espresso glass when it is relatively meaningless?

You just reminded me that I actually have weights for calibration that I have from an old antique scale that I inherited. I'd have to say that 4/100th of a gram is pretty darn close.

lessthanjoey
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#7: Post by lessthanjoey »

Vindibona1 wrote:What good is it to have a marked espresso glass when it is relatively meaningless?
None.

kris772
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#8: Post by kris772 »

I have a small graduated 50ml "beaker" . I use it to put markings on the container(s) I brew into to help with the vol, but weight is what is important for reasons discussed.
Life is too short for bad espresso! - Thunk-ed, NOT stirred!