[quiff]

Disclaimer – I’m well aware this is both a first world problem, and highly unlikely to affect the quality of my coffee, I’m just interested in principle, particularly views from anyone in metrology / engineering / science fields. 

I was recently given some coffee scales, which are supposedly accurate to 0.1g. (For context, to make an espresso you use just e.g. 18g of beans, so in theory being able to tell the difference between 18g and 18.9g of beans could make a difference to flavour (see disclaimer). The scales are not hugely expensive, but are from a reputable kitchenware brand. 

I usually ‘pour’ beans in, then slow down as I close in on 18g. I noticed that if I poured to 17.Xg and then added beans slowly as I closed in on the magic number, it seemed impossible to get the scles to move in 0.1g increments – I could add say 3 beans before they changed, and then they would jump by 0.2 – 0.3g.

As a test, I then saw how many beans I could add to an empty scale before it registered anything. If I added the beans one, two, three etc at a time, I found it was possible to weigh (what turned out to be) 20+g of beans without the scales registering anything at all. I found that the scales wouldn’t register anything unless I added 7 or more beans at a time. I appreciate it’s variable, but 7 beans seems to weigh about 1g, putting each bean at more than 0.1g.

Are the scales faulty? Or am I misunderstanding what accurate to 0.1g means?      

 

           

Topic

[mdavidford]

I don’t even use a spoon for

I don’t even use a spoon for my instant…

[mdavidford]

quiff wrote:

Just seems a bit suspect to say it has 0.1g precision if a single bean which weighs more than 0.1g can’t provide the force to register

It does have 0.1g precision. It just doesn’t have 0.1g accuracy.

[Edit: should have finished reading through the thread – HP got there before me.]

[mdavidford]

quiff wrote:

I probably deserved that. Of course, the follow on question is whether I can trust my scales to weigh 100 beans accurately in the first place. 

Take 100 sets of scales and repeat it on each of them, then score them on (a) variance (low to high), and (b) proximity of the mean reading for that scale to the median mean of all scales, then use the scales that have the best combined score.

[hawkinspeter]

Backladder wrote:

Having used bensynnock’s method to accurately determine how many beans you need use a pill counting tray to measure the correct number.

https://www.amazon.co.uk/Medicounter-Professional-Triangle-Tablet-Counter/dp/B0BC4QKSHC/ref=asc_df_B0BC4QKSHC?mcid=844dc743145e369b83ddbb7d22ef54a5&tag=googshopuk-21&linkCode=df0&hvadid=697277231999&hvpos=&hvnetw=g&hvrand=4299720761858751111&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9208099&hvtargid=pla-1885707681772&hvocijid=4299720761858751111-B0BC4QKSHC-&hvexpln=0&gad_source=1&th=1

How does that work for different size beans?

[Backladder]

Having used bensynnock’s

Having used bensynnock’s method to accurately determine how many beans you need use a pill counting tray to measure the correct number.

https://www.amazon.co.uk/Medicounter-Professional-Triangle-Tablet-Counter/dp/B0BC4QKSHC/ref=asc_df_B0BC4QKSHC?mcid=844dc743145e369b83ddbb7d22ef54a5&tag=googshopuk-21&linkCode=df0&hvadid=697277231999&hvpos=&hvnetw=g&hvrand=4299720761858751111&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9208099&hvtargid=pla-1885707681772&hvocijid=4299720761858751111-B0BC4QKSHC-&hvexpln=0&gad_source=1&th=1

[hawkinspeter]

Creakingcrank wrote:

Apologies for triggering! I think Quiff is talking about beans here though, and they could control the process a bit by putting a sticker that says “no squishing” on the side of their measuring pot 🙂 

Measuring things by volume makes even less sense when the objects are larger (I’ve seen a U.S. recipe that listed a cup of fresh apricots FFS). With irregularly sized objects, the order in which you put them in the container can make a difference and also, how do you determine if you’ve optimally packed the beans?

https://en.wikipedia.org/wiki/Packing_problems

I think it’d be easier to use an 8-dimensional volume and hand-carve the beans into perfect spheres as that way, you can use the optimal E8 lattice packing.

[kinderje]

Great fun reading the

Great fun reading the comments.

My solution is to put a Nespresso pod in the machine and then press espresso or lungo.

<<lobs grenade into discussion and retires very quickly>> 

[Creakingcrank]

Apologies for triggering! I

Apologies for triggering! I think Quiff is talking about beans here though, and they could control the process a bit by putting a sticker that says “no squishing” on the side of their measuring pot 🙂 

[hawkinspeter]

Creakingcrank wrote:

BECAUSE THIS IS AN IMPORTANT ISSUE, I have just tried loading my digital scales with cocktail sticks (approx weight 0.2g) one at a time. I have no coffee beans.  I see similar behaviour to that you describe. I suspect the scale is doing some kind of processing to filter out electrical noise, resulting in small changes not being registered.

One solution would be to lift the receptacle you use to hold the beans off the scale between additions.

When I was at university (a long time ago) we had to do a lab where the task involved making a sintered metal part (powdered material heated and squashed together) The part need a certain mass of material to be right, but we had to propose ways of making them quickly.  The problem was that the weighing systems we had took time to stablise, so it was difficult to do “fill until right weight” as you have found. 

The answer turned out to be doing it by volume instead: making a “cup” of the right size to hold near-enough the right weight of material when filled to the top. Could you do that? I’m thinking about the scoops one uses for e.g., infant formula or protein shakes, where you are encouraged to “level off” the load with a knife to get a consistent amount in each scoop.

Then, obviously, do some blind tasting with slightly different amounts to see what tolerances your palate can tolerate!

I’m properly triggered by that.

I hate the U.S. system of measuring cooking ingredients by volume – it makes no sense at all which is why every other country in the world uses weights.

The “volume” of coffee grinds would depend on whether it’s tamped (and what force is used for tamping) and the size of the grind.

[Creakingcrank]

BECAUSE THIS IS AN IMPORTANT

BECAUSE THIS IS AN IMPORTANT ISSUE, I have just tried loading my digital scales with cocktail sticks (approx weight 0.2g) one at a time. I have no coffee beans.  I see similar behaviour to that you describe. I suspect the scale is doing some kind of processing to filter out electrical noise, resulting in small changes not being registered.

One solution would be to lift the receptacle you use to hold the beans off the scale between additions.

When I was at university (a long time ago) we had to do a lab where the task involved making a sintered metal part (powdered material heated and squashed together) The part need a certain mass of material to be right, but we had to propose ways of making them quickly.  The problem was that the weighing systems we had took time to stablise, so it was difficult to do “fill until right weight” as you have found. 

The answer turned out to be doing it by volume instead: making a “cup” of the right size to hold near-enough the right weight of material when filled to the top. Could you do that? I’m thinking about the scoops one uses for e.g., infant formula or protein shakes, where you are encouraged to “level off” the load with a knife to get a consistent amount in each scoop.

Then, obviously, do some blind tasting with slightly different amounts to see what tolerances your palate can tolerate!

[hawkinspeter]

Incidentally, to continue the

Incidentally, to continue the other coffee related thread, I discovered someone selling elephant dung coffee: https://blackivorycoffee.com/

There’s definitely diminishing returns when you start paying those kinds of prices for coffee (£150 for 40g).

[bensynnock]

The accuracy of the scales
The accuracy of the scales becomes less important the more beans you use.

You could always use a known weight to test the accuracy of the scales.

[hawkinspeter]

quiff wrote:

hawkinspeter wrote:

Anyhow, you’re better off weighing the ground coffee.

That’s a fair point. Experience with my grinder shows that weight of beans in = weight of grounds out (albeit some of that weight out will be retention from the previous grind). Just seems a bit suspect to say it has 0.1g precision if a single bean which weighs more than 0.1g can’t provide the force to register, so that you can add 20+ g slowly without changing the reading.    

They’re kitchen scales and thus not particularly sensitive. There’s also the difference between precision and accuracy – they might have 0.1g precision but only be accurate to within +-0.5g. If you want accuracy, go for some chemical scales that are usually in a glass case to prevent air movements from disrupting the measurement.

Personally, I’m too lazy to weigh my coffee all the time – I use a Baratza Sette 270 which has a time setting and grind directly into an Aeropress for 5 seconds. (The Baratza is somewhat overkill for Aeropress coffee which doesn’t demand as much accuracy as espresso).

[bensynnock]

Exactly. There’s nothing
Exactly. There’s nothing wrong with including even further variables in the study – any that don’t have a statistically significant effect can be discarded during the analysis.

Personally, I just fill the container with coffee and tamp it down a bit.

[quiff]

hawkinspeter wrote:

Anyhow, you’re better off weighing the ground coffee.

That’s a fair point. Experience with my grinder shows that weight of beans in = weight of grounds out (albeit some of that weight out will be retention from the previous grind). Just seems a bit suspect to say it has 0.1g precision if a single bean which weighs more than 0.1g can’t provide the force to register, so that you can add 20+ g slowly without changing the reading.    

[Author]

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