# Wilfa Uniform Grind Size Analysis



## grind (Sep 26, 2020)

I've had a Wilfa Uniform for a few weeks now, it took a while to get dialed in but I'm able to make an OK V60 with a grind size around 32 (coarse). If i grind any finer than 28 (this is still supposed to be pretty coarse) then the filter starts clogging, brew times go up significantly & I start getting astringency + bitterness.

I'm still not blown away with anything I've made so far & was expecting a little more from this grinder. Given I feel like I've got water & technique pretty under control by now, I naturally want to try and blame the grinder. Also, it seems most V60 recipes other than the 4:6 method recommend a much finer setting than i'm using, but it seems impossible to make those work. Happy to accept that my technique may just be bad, but it would be great to rule out any grinder issues to start with. If anyone is wondering i'm using: V60 4:6 method - 18g/300ml- Third Wave Water @ 90c, Square Mile La Bolsa beans.

To try and analyse this scientifically, I ran an image on grind size 32 (sample section below) through the Coffee Ad Astra particle size analysis software & got the grind size distribution below.

The grind image by eye doesn't look great to me - I have no experience here so it would be great to get some other thoughts, but there seem to be a large number of really fine particles in there, especially given the coarse setting. The software results don't look great either - comparing the distribution histogram to ones I've seen for other grinders it looks significantly less peaked than it should for a grinder of this quality at a coarse filter setting.

Would be great to get people's thoughts, especially others who have the Uniform or other grinders of similar quality.


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## grind (Sep 26, 2020)

I did another run after a grinder clean, a closer photo to improve resolution for better capture of the fines & also some post processing to remove shadows. The diameter distribution is a touch tighter, but not much, 470 microns vs. 490 in the first run.

Does anyone know of a database where people are storing results of this analysis data for different grinders?


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## earthflattener (Jul 27, 2015)

Looks like a nice experiment. I must see if someone has done the same with a Niche (or maybe even do it myself). Just by pure eyeball, my Niche grainsize does appear to have less fines.

It may be a little bit difficult to get answers you can trust for direct comparison though. The problem of inferring 3d granulometry from 2d images is part of stereology and is a non-trivial inverse problem. I can see a number of things that might need to be managed properly to get good results. Static electricity being one, rugosity being another. For example, consider that we have 3d ellipses, all exactly of the same size and with axial dimensions, x<y<z. When the grain falls on the paper, since it is small, static may prevent it from lying on its longest surface, so that even though the distribution of grain size should be exactly constant, the apparent 2d size will vary. Adding rugosity (i.e grains are 'bumpy') will only make this (far) worse. So there is a natural spread just associated with projection

That said, your grain size distribution does look a bit grim


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## earthflattener (Jul 27, 2015)

My grind... for V60. 50 on the dial on the Niche


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## MWJB (Feb 28, 2012)

I'm not sure those plots make much sense. You're saying the grind acts as if it is finer on the Wilfa, but the avg particle diameter is 1200um in the plot...1200um is very coarse.

I found I got similar performance from my Wilfa at 18-19, same protocol on the Niche was around 54.

Make a video of your V60 brew, that might be more useful. Make sure you are using Japanses papers.



earthflattener said:


> When the grain falls on the paper, since it is small, static may prevent it from lying on its longest surface, so that even though the distribution of grain size should be exactly constant, the apparent 2d size will vary.


 @earthflattener hi, sorry can you explain this a bit please? Why should the grain size be exactly constant?


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## earthflattener (Jul 27, 2015)

Yeah, I didn't mean that the grainsize is constant in the real world. It clearly isn't. What I meant is that the measurement technique introduces variability due to the projection...and this could be large - although not as large as the spread we are seeing in grind's photo.

So, instrad of an ellipse, lets think that each grain is exactly a sugar cube shape of lengths x,y and z. Then it has 3 different size faces, of size xy, xz and yz respectively. So if you are looking down at a page filled with these sugar cubes and measure the area of the objects, you see a histogram with 3 different sizes. Most likely the biggest side will fall flat, but there will be some of the smaller ones. If static elecricity is playing a part then they will 'stick' quicker to the paper instead of tumbling to the lowest energy state, and the smaller sides will have a bigger chance of occurring. So, even though all our 3d sugar cubes are the same size, we see a spread of values from a 2d image of them - and that spread depends on how elongated the grains are.

In the real world, out grain shape depends on the grinder (presumably there is a systematic difference between flat and conical burr) and the rugosity means that there will not be only three possible projections but a huge number, so even if all our objects had the same 3d shapre, they would have a spread histogram of 2d projections on a sheet of paper. Is this important? Well, on my little niche sample I could clearly see that some grin were taller than they were wider when on the paper, so it certainly happens...and I think a spread factor of 2 or more is quite likely. Again, Mr/Ms grain's example is much worse than that. There are clearly a lot of fines - so it is not just a question of 2d/3d coherence.

I was also thinking the size in his pictures is very large 1.2 mm is a pretty big coffee grain. However, somehow you would have to enter scale into the image analysis program. It could be that the scale is wrong


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## grind (Sep 26, 2020)

MWJB said:


> I'm not sure those plots make much sense. You're saying the grind acts as if it is finer on the Wilfa, but the avg particle diameter is 1200um in the plot...1200um is very coarse.


 Correct, from the software stats: mean diameter ~ 1100um, sigma ~ 470um. My understanding is that this is more of a french press grind than a V60 setting usually?

Video below of the attempted technique: https://streamable.com/loupcn - 4:6 method (18g/300mL - TWW (Classic) - 50/70/60/60/60g every 45s) and intentionally pouring quite fast @ ~6g/L. I'm using the 02 Japanese papers I think (the ones with no tab that come in a box of 40?).

Result is OK & now pretty consistent - but I've had significantly better pour overs & batch brews in coffee shops, with more clarity, juiciness & particularly sweetness than I'm able to get. As I go finer from here, even a few clicks I get noticeable astringency & bitterness with the same technique.


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## grind (Sep 26, 2020)

earthflattener said:


> I was also thinking the size in his pictures is very large 1.2 mm is a pretty big coffee grain. However, somehow you would have to enter scale into the image analysis program. It could be that the scale is wrong


 Scale is good, I used the penny (20.3mm diameter) to calibrate with pixel level accuracy & ran twice on different photos achieving exactly the same distribution mean both times.


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## MWJB (Feb 28, 2012)

grind said:


> Correct, from the software stats: mean diameter ~ 1100um, sigma ~ 470um. My understanding is that this is more of a french press grind than a V60 setting usually?
> 
> Video below of the attempted technique: https://streamable.com/loupcn - 4:6 method (18g/300mL - TWW (Classic) - 50/70/60/60/60g every 45s) and intentionally pouring quite fast @ ~6g/L. I'm using the 02 Japanese papers I think (the ones with no tab that come in a box of 40?).
> 
> Result is OK & now pretty consistent - but I've had significantly better pour overs & batch brews in coffee shops, with more clarity, juiciness & particularly sweetness than I'm able to get. As I go finer from here, even a few clicks I get noticeable astringency & bitterness with the same technique.


 You can't even extract a French press at 1100um. 800-900um would be as coarse as I would go & that would be for an insulated 1 hour steep. A small glass press might need 400-450um avg.

That std dev makes no sense to me

You're pouring really aggressively, the stream is hosing from the kettle spout in an arc. Try to get it to drop down straight from the spout. If your flow rate is about 1.4g/sec from the brewer, there is no need to get the water in quite so quickly. See if you can get the pulses in around 25-30s each. (e.g. pour at 2g/sec or even a bit slower). If you get standing liquid above the bed when it's time for the next addition, you can pour straight down the middle (less cloggy & silty).


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## grind (Sep 26, 2020)

MWJB said:


> You can't even extract a French press at 1100um. 800-900um would be as coarse as I would go & that would be for an insulated 1 hour steep. A small glass press might need 400-450um avg.
> 
> That std dev makes no sense to me
> 
> You're pouring really aggressively, the stream is hosing from the kettle spout in an arc. Try to get it to drop down straight from the spout. If your flow rate is about 1.4g/sec from the brewer, there is no need to get the water in quite so quickly. See if you can get the pulses in around 25-30s each. (e.g. pour at 2g/sec or even a bit slower). If you get standing liquid above the bed when it's time for the next addition, you can pour straight down the middle (less cloggy & silty).


 There doesn't seem to be much data around online, but I thought around 1000um was pretty much the target for french press? What's wrong with the standard deviation, it's too small, too large? The stdev of a Baratza Forte calibrated to the same micron average is around 420um, so maybe mine is too low (https://coffeeadastra.com/2019/04/07/an-app-to-measure-your-coffee-grind-size-distribution-2/).

Yes, my flow rate is ~6g/s. I was pretty much following this video, flow rate is >10g/s here: 



. Hoffman/Perger/Rao all suggest flow rates in the 5-8g/s range. Bear in mind that my gooseneck has a tiny spout, this isn't a full size kettle just a little 300ml pot from Amazon with a 5mm diameter spout - so water arcs out of it even at slower flow rates.

What's the advantage of the slower 2g/s flow rate that you suggest? Also, I assume I'd need to grind a fair bit finer to get that slower rate to work?


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## MWJB (Feb 28, 2012)

grind said:


> There doesn't seem to be much data around online, but I thought around 1000um was pretty much the target for french press? What's wrong with the standard deviation, it's too small, too large? The stdev of a Baratza Forte calibrated to the same micron average is around 420um, so maybe mine is too low (https://coffeeadastra.com/2019/04/07/an-app-to-measure-your-coffee-grind-size-distribution-2/).
> 
> Yes, my flow rate is ~6g/s. I was pretty much following this video, flow rate is >10g/s here:
> 
> ...


 The coffeeadastra measurement method isn't comparable to any known, or useful method. The stdev can't be 470, or 420, it will be one factor under the average and another over the average, as the stdev will appear to decrease as the grinds get bigger (typical with LPA, but much less so with ISO sieves). It's not that I think it is wrong within the confines of its own convention, it's more that I don't see that it has been correlated to any existing convention. So it's impossible to interpret.

MIT determined in the mid 50's that a coarse grind won't extract properly in 20mins at a constant temp. ~720um (Silex grind, but also adopted by SCAA for cupping & note this is finer than manual drip grind at 840um avg) was the specified grind for a constant temp immersion, but declining temp generally needs to be smaller. The whole coarse grind for French press was the absolute worst advice ever issued & then got commonly repeated.

It's more that there is no advantage to a fast pour rate, for a normal brew time...you're hosing the bed, causing unnecessary clogging, but your brew time isn't any quicker than using a gentler pour, which flushes less silt into the cup (you may be able to also use a coarser grind with a slower pour which will have less small particles in to start with). My 24g:360g V60s at 81 to 82 (45g poured every 20sec) on the Niche, are done in less than 3:00 pouring at an average speed of just over 2g/sec. (brews are a bit bigger so I'd expect a slightly faster pour/flow rate).

The 4:6 method isn't used by Rao (who both Hoffmann & Perger are imitating). Rao is brewing with a much finer grind (~40 Niche) than Kasuya in the video you link to. I can't get Rao's latest method to work at all. Even so, Kasuya takes 2:49 to get the water in, that's an average of 1.78g/sec...so why kick up the bed more than you need to? The biggest problem in drip brewing is getting a decent extraction & keeping excessive silt out of the cup.

The coarser the grind the slower you need to pour because you are determining the flow rate.


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## grind (Sep 26, 2020)

Take your point, on the methodology not being widely used. Still, if anyone has run this same method on their own grinder I'd be interested in the results - I don't really see another option for calibrating grind size/quality at home (other than Kruve maybe).

I'll have a go with a slower flow rate & finer grind this morning & report back.


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## grind (Sep 26, 2020)

This morning's test was a bit of a failure, I tried 2 brews with 28 (coarse/Rocky sand) & then 24 (regular sand) grind setting. 2g/s flow rate in a similar regime to 4:6. All water was in by around 3:15 & stopped the brew at 3:45.

Both were extremely underextracted: sour, incipid, watery, vegetal, first cup was one of the worst tasting cups I've ever managed. No astringency though & water is still draining quickly, so obviously the slower pouring is not clogging the filter like my aggressive pouring was.

Guess I'll keep going finer?


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## MWJB (Feb 28, 2012)

grind said:


> This morning's test was a bit of a failure, I tried 2 brews with 28 (coarse/Rocky sand) & then 24 (regular sand) grind setting. 2g/s flow rate in a similar regime to 4:6. All water was in by around 3:15 & stopped the brew at 3:45.
> 
> Both were extremely underextracted: sour, incipid, watery, vegetal, first cup was one of the worst tasting cups I've ever managed. No astringency though & water is still draining quickly, so obviously the slower pouring is not clogging the filter like my aggressive pouring was.
> 
> Guess I'll keep going finer?


 Yes, go finer.

You say you "stopped the brew", how? Your brew will be most consistent if you let them drain out naturally, at your brew size another 5g in the cup will mean more than half a %EY.

Yes Kruve (400 &1600 most useful with 0.01g scales) is a quick way to get a rough take on overall coarseness/fineness (within class of grinder - Porlex/KG79/ vs Feld/Niche/Wilfa Uniform vs EK-43/Apex/Forte BG), also for filter 600um & 1180um ISO/ASTM sieves, can be had in 3" sizes.


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## grind (Sep 26, 2020)

MWJB said:


> Yes, go finer.
> 
> You say you "stopped the brew", how? Your brew will be most consistent if you let them drain out naturally, at your brew size another 5g in the cup will mean more than half a %EY.


 Bit delayed but I finally got round to trying this method again today.

Ground at 18 (table salt / fine sand) - similar regime to my 4:6 above (50/70/60/60/60g every 45s), but pouring at 2g/s or slower. All water was in by 3:30, but this time it took until around 5 minutes until bed was dry.

When i say stopping brew - i just mean lifting V60 around 10-15s after the bed is dry.

Result is now drinkable, more fruity/sweet notes coming through, but still quite sour. No astringency yet & still tastes quite clean.

Maybe i need to go finer again - but it seems the drawdown is taking too long given finished at 5 mins, do I need to worry about that or not?


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## MWJB (Feb 28, 2012)

grind said:


> Bit delayed but I finally got round to trying this method again today.
> 
> Ground at 18 (table salt / fine sand) - similar regime to my 4:6 above (50/70/60/60/60g every 45s), but pouring at 2g/s or slower. All water was in by 3:30, but this time it took until around 5 minutes until bed was dry.
> 
> ...


 Cool, on the stopping, I had worried that you were pulling the brewer before it drained (bad idea).

If it still seems to be under, then sure go finer. If it's tasting good then a 5:00 brew isn't a problem. If bothered, you could lop some brew time off by reducing the time between pulses.


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## grind (Sep 26, 2020)

MWJB said:


> Cool, on the stopping, I had worried that you were pulling the brewer before it drained (bad idea).
> 
> If it still seems to be under, then sure go finer. If it's tasting good then a 5:00 brew isn't a problem. If bothered, you could lop some brew time off by reducing the time between pulses.


 Went down to a 16 grind on the Wilfa Uniform, but now I'm getting some bitter/sour confusion & can't quite tell... I think there's still a sour aftertaste there but could be wrong. Ran out of the Japanese filter papers so more on order before trying again.

Having been through 2 bags of Square Mile La Bolsa - I went to my local coffee shop the other day & tried their batch brew, which happened to be La Bolsa too. It tasted like a completely different bean to what I'm achieving in my pour over. The batch brew was nice & sweet with really strong orange flavours (matching the tasting notes on the bag), but I'm not getting close at home.

Am I asking for too much to match coffee shop quality filter at home?


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## MWJB (Feb 28, 2012)

grind said:


> Went down to a 16 grind on the Wilfa Uniform, but now I'm getting some bitter/sour confusion & can't quite tell... I think there's still a sour aftertaste there but could be wrong. Ran out of the Japanese filter papers so more on order before trying again.
> 
> Having been through 2 bags of Square Mile La Bolsa - I went to my local coffee shop the other day & tried their batch brew, which happened to be La Bolsa too. It tasted like a completely different bean to what I'm achieving in my pour over. The batch brew was nice & sweet with really strong orange flavours (matching the tasting notes on the bag), but I'm not getting close at home.
> 
> Am I asking for too much to match coffee shop quality filter at home?


 I'd expect the batch brew to be cleaner/clearer, less mouthfeel, but as to flavour generally, I would expect them to be recognisably similar.

You should be able to make very enjoyable pourover at home.

Push through the bitter (go finer), see if there is a point where the sour diminishes & the bitter let's up too. I doubt you're over extracting at this point, the bitterness could either be where you are just getting into the desired range, or a little too much agitation. If, with the finer settings, you are getting standing liquid in/during the later pours, lay off the spiral pouring when this happens & go straight down the middle.

If you want very clean cups, you are better off brewing with coarser grinds & using more & smaller pulses. But I'd persevere with your current approach for now and explore a new regime after achieving ball-park cups (even if their not quite as clean as batch brew).


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## grind (Sep 26, 2020)

MWJB said:


> I'd expect the batch brew to be cleaner/clearer, less mouthfeel, but as to flavour generally, I would expect them to be recognisably similar.
> 
> You should be able to make very enjoyable pourover at home.
> 
> ...


 Yeah, I'm definitely a fan of a cleaner cup, but it was unrecognisable so I'm definitely missing some sweetness & acidity at home.

Just tried a couple at 15 & 14 grind, same regime although without Japanese filters until the new ones arrive. It's getting better still, the 14 grind cup has a hint of bitterness I think but not too bad so will keep going finer...

Have to admit I don't really understand coffee... how is it possible that I made decent cups with a coarse french press grind, aggressive pour & 3:30 brew time while a medium-fine grind is ending up under-extracted with a gentle pour?


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## MWJB (Feb 28, 2012)

grind said:


> Yeah, I'm definitely a fan of a cleaner cup, but it was unrecognisable so I'm definitely missing some sweetness & acidity at home.
> 
> Just tried a couple at 15 & 14 grind, same regime although without Japanese filters until the new ones arrive. It's getting better still, the 14 grind cup has a hint of bitterness I think but not too bad so will keep going finer...
> 
> Have to admit I don't really understand coffee... how is it possible that I made decent cups with a coarse french press grind, aggressive pour & 3:30 brew time while a medium-fine grind is ending up under-extracted with a gentle pour?


 I thought the coarse grind, aggressive pour cups weren't that decent, hence trying something else? My guess would be the coarser grind brews were still under-extracted, but the aggressive pouring bolstered up the non-dissolved solids, rounding out the cup. Under-extraction is the more common fault, whatever the grind & pour regime has to dovetail with grind.


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## Hestu (May 3, 2020)

Not sure if you got anywhere with solving your issues @grind but my Uniform required quite a lot of alignment to get the grind to an acceptable uniformity.


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## Mrboots2u (May 10, 2013)

Hestu said:


> Not sure if you got anywhere with solving your issues @grind but my Uniform required quite a lot of alignment to get the grind to an acceptable uniformity.


 What was acceptable uniformity , how did you measure it , how did you measure the alignment


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## grind (Sep 26, 2020)

Hestu said:


> Not sure if you got anywhere with solving your issues @grind but my Uniform required quite a lot of alignment to get the grind to an acceptable uniformity.


 Well, I'm not sure if there are issues yet since has been hard to find comparable data to check against, but I'm not sure the distributions in my first 2 posts are as bad as I originally though.

That's interesting though - how did you adjust alignment? I have no experience with that.


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## grind (Sep 26, 2020)

MWJB said:


> I thought the coarse grind, aggressive pour cups weren't that decent, hence trying something else? My guess would be the coarser grind brews were still under-extracted, but the aggressive pouring bolstered up the non-dissolved solids, rounding out the cup. Under-extraction is the more common fault, whatever the grind & pour regime has to dovetail with grind.


 The extra-coarse cups were OK - like 7/10 with no unpleasant flavours e.g. sourness, bitterness or astringency - however they were definitely missing intensity of the good acidity & sweetness that I knew the beans are capable of. Due to lack of sourness I assumed they were not under, but maybe there are different types of under extraction. It must be possible not to underextract a V60 coarse since that's what the original 4:6 method suggests.

Would not say that any of my finer grind attempts have been 'better' yet, they are probably getting to around 6-7/10 but still hints of unpleasant flavours floating around in there -> will keep going finer for now.


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## MWJB (Feb 28, 2012)

grind said:


> It must be possible not to underextract a V60 coarse since that's what the original 4:6 method suggests.


 There's no reference to extraction at all regarding the 4:6 method.

It's important to realise not all cups can be 10/10. To qualify as specialty they only need to be 8/10 (not all achieve this). Almost no coffee available exceeds 9/10, even if you brewed it perfectly. So achieving, say, 8.5 out of 10 on avaerge seems perfectly reasonable & feasible. Sometimes there's no point trying to bang a square peg into a round hole. So, scores apart, if I tend to prefer Rwandan, Kenyans & Colombians, I'm only going to invest Brazils that really pique my interest. Stack the odds in your favour & chase down the coffees you know that you are most likely to enjoy.


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## grind (Sep 26, 2020)

MWJB said:


> There's no reference to extraction at all regarding the 4:6 method.


 Not sure I understand what you mean?



MWJB said:


> It's important to realise not all cups can be 10/10. To qualify as specialty they only need to be 8/10 (not all achieve this). Almost no coffee available exceeds 9/10, even if you brewed it perfectly. So achieving, say, 8.5 out of 10 on avaerge seems perfectly reasonable & feasible. Sometimes there's no point trying to bang a square peg into a round hole. So, scores apart, if I tend to prefer Rwandan, Kenyans & Colombians, I'm only going to invest Brazils that really pique my interest. Stack the odds in your favour & chase down the coffees you know that you are most likely to enjoy.


 Yeah, fair point. My 7/10 is scored relative to the best brewed coffee I've personally had - If i normalised to 10 being best possible coffee in the world as you suggest, then I'm probably hitting 6/10 on average with V60 at the moment. I've managed a few cups at home on Aeropress, seemingly via fluke which I'd score an 8, but again my average is no better than 6.5/10.

Agree on the beans - I'm generally sticking with Colombians, Bourbon/Caturra until I learn how to maximise the sweet, chocolate notes from those. Have played around with some fruity light roast Ethiopians which are interesting, but leaving that for now.


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## MWJB (Feb 28, 2012)

grind said:


> Not sure I understand what you mean?


 Kasuya presumaby used this technique at least a few times before he switched to the other method, with a few different coffees, so it would be easy to just measure a few, note the grind size (rather than just pictures) and give an average extraction yield (maybe he did & I missed it)..


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