DamianWarS wrote:He addresses that saying if you asked him a year earlier he'd say your crazy. I don't know if that makes you feel more confident about his latest remarks but at least he recognises the change in direction. His solution using a v60 is to ensure the water line doesn't get to high which would have a greater effect on bypass. The alternative solution is a flat bottom brewer with a sufficient textured bottom so as to prevent the filter from sealing to the brewer and increasing the surface area where water passes through.

The effect are similar to using a stand alone metal filter where you can visually see water moving on the outside of the filter where water is bypassing the coffee bed. Using paper filters with ridged brewers the same thing is happening you just don't see it as much. Where using a ridgeless one seals the filter to the brewer and the only escape is the bottom part but then it gets clogged. So the ridged system is important in cone brewers to prevent clogging but at the expense of bypass. I think the fact that a ridgeless brewer clogs the filter and the ridged brewers does not agrees with gangne's suggestion of bypass happening.

Oh don't get me wrong its absolutely a good thing that someone can admit they're wrong and even seek out to prove it. I guess i just find it odd how (mostly Rao) is going about it. He's on this pursuit to find the ultimate no bypass method but i never really see him talk about why bypass is a bad thing. Maybe i missed it. In the end all knowledge is good, the more info the better. I think social media just makes things a little cloudy as to the reasoning behind something.

On my own a couple of years back I began to test the v60 thinking the filter is causing a lot of problems and to remove it and put an areopress filter at the bottom with elastics. I thought for sure this will produce a more even extraction but the same thing happen to me as it did Gagné, the filter got clogged and the draw down was really slow and it didn't make a good cup.

My thoughts at the time was the cause was not byass but fines migration fines get dispersed and trapped across a large surface area of the filter essentially acting as a large net to capture the fines where with a very small area of filter over the bottom opening too many fines got stuck just at the bottom having no other place to go and it's stalls the drawdown.

That was my conclusion a couple years back however bypass wasn't part of my thought process and to be honest I still think fines migration may still be a factor as setups like that nothing sticks to the walls so the fines are being concentrated more in the coffee bed until they find something to stick to (the little bit of filter at the bottom).

What points it to bypass over fines migration (even if fines migration contributes) is if you're using a smooth walled brewer the filter seals itself on the brewer not allowing bypass along the walls but it would still allow capturing the fines. If that setup still clogs the filter than fines migration is less of a factor than bypass and this is exactly what Gagné does testing how a smooth walled brewer performs and it doesn't perform well concluding that bypass is part of the design of a v60s extraction.

I drank the koolaid and I'm on the bypass train but I want to be able to run my own test to know the impact. But I think one of Gagné more significant claims is that without bypass you can dial in ratio and get higher extraction. I'm not sure what Rao claims or what kind of stuff he is doing. The only think I know from Rao about bypass is from his last pour over demo video where he adds a tea strainer to the bottom which is the same thing Gagné does.

DamianWarS wrote:What points it to bypass over fines migration (even if fines migration contributes) is if you're using a smooth walled brewer the filter seals itself on the brewer not allowing bypass along the walls but it would still allow capturing the fines.

Don't think we can say with confidence what contributes more to the slow drawdown. Just want to add that the filter area that doesn't contribute to flow will not be as effective in trapping fines.

I've found this whole concept interesting but it's quite frustrating to dial in and the results have been all over the place. Sometimes great, sometimes terrible but always a nuisance. It feels liberating to brew with a normal V60 and know that perhaps it won't be perfectly extracted but overall pretty good and fast.

I can agree with that. Using the aeropress as a gravity dripper has had its caveats.

Fines clogging the filter makes a lot of sense. Look at any v60 brew and the whole filter is coated when the drawdown is done. Now picture concentrating all of that to a much smaller area.

The other thing with a v60 for example is the idea that all of extraction must be from percolation moving straight down through the bed. I never understood why one would think that. It's obvious that much of the extraction is immersion. The "bypass" isn't plain water but instead already extracted coffee filtering through path of least resistance.

I guess it's kinda of like the clever or aeropress. Both percolation and immersion, the question is how does it change the result as you force it further and further towards percolation.

cgibsong002 wrote:Fines clogging the filter makes a lot of sense.

This is what I thought, but an experiment I did today with a mesh filter inside the filter paper made me wonder. Fines migration is a real thing as far as I'm concerned - the paper filter had a thick muddy layer of fines all over while the grounds left behind in the mesh looked like they had been sieved.

The interesting thing is that drawdown was very fast, about double the speed than without the additional mesh.

Agreed about the immersion - I don't feel bypass is such a bad thing - but to answer your question, from experience extra percolation will increase extraction.

Jonk wrote:...from experience extra percolation will increase extraction.

Is it extra percolation or is it less bypass due to the water not being so high in the dripper with more pours. Also the moving coffee particles are less of a resistance and might enable the water to find the way of lowest resistance straight down.

Just brainstorming here really

If pure percolation was ideal then why wouldn't a standard aeropress recipe also be ideal? 0 bypass and you can control exactly how fast the percolation occurs. This is all very confusing.

Jonk wrote:I don't feel bypass is such a bad thing - but to answer your question, from experience extra percolation will increase extraction.

like the way everything in coffee is turning into, if you can't control it then it's a bad thing. This is almost like when sifting got really popular and then all of a sudden people starting figuring out that fines are not all evil and we don't have to sift them out. I'm quite certain Hario's R&D department probably tried a ridgeless brewer and realized the ridges are a good thing.

borrowing notes from Gange and Rao I decided to cut a tea strainer into the size of an aeropress filter. I put the cut out mesh inside the cap, then added the paper filter and fit it to the bottom of the aeropress. it's a more snug fit off course but works perfectly fine. I did a classic pourover method, 20g coffee/300ml water. add coffee, add 60ml water for bloom with agitation, start main pour at 40-45sec. single pour until 300g, a gentile stir and wait. The drawdown was faster than without the mesh and the total brew time was 4:30. previously with the same grind it was 7 min. So despite the cap having a bunch of holes on it the paper filter is still sealing to the flat areas of the cap and the only flow happening is where the holes are, adding a mesh between the paper filter and cap creates a much larger surface area for free flow as the filter isn't really sealing to anything and limiting the flow (or if it is it's very minimal). It was a bit stronger brew than a v60 but extracted well, not astringent in the least bit or a feeling of under/over extracted. so the mesh helps and I'm a little surprised that it did so well because I thought the many holes in the cap were doing a good job but clearly not. I'm sure the mesh would help a more even extraction even with the plunger as flow is not being limited to just where the holes are. makes me wonder if I just cut the bottom of the cap out with a little rim for the mesh to sit on and silicon seal it in place what impact it would have on the drawdown as a gravity dripper of even with the plunger. It would be eliminated in competition as you have to use the original cap (and I'm sure a modified one wouldn't sell) but it would be interesting how well it would work.