I'd like to share you some small updates about what I've been experimenting with this last week. As you'll see, I like to work on many things at once, and this has been made much easier with your support, as it allowed me to order a lot of the material described below !
I've watched this awesome video about aerogels by Veritasium, and seeing the amazing insulating properties of aerogels made me want to experiment with it for V60 brewing. So I've ordered some cheap aerogel sponges on Amazon; I'm curious to see what happens to the slurry temperature if I stick that inside a glass V60.
I'm pretty sure that these sponges are not food grade though, so if it turns out to be useful inside a V60 I'll need to coat it with something else on top that is food grade.
I might also make a custom kettle coat for my Brewista Artisan Gooseneck with it. I know about brewcoat, but I couldn't find information on whether their coats would fit my kettle, and aerogels should also be way more insulating !
Scott Rao's recent post about using a paper filter on top of the coffee puck to achieve very high extraction yields got me thinking a lot about channeling and astringency. My best running hypothesis is now that astringency is caused by heavy molecules really hard to extract. Those would only be extracted inside channels in a percolation brew, but the big change for me is this: I think channeling has more to do with the structural integrity of the coffee bed than the uniformity of particle sizes.
When you add water on top of the bed, it will displace particles that are too light (i.e. small) and dig a channel. Once you have a channel, water will pass there more easily and displace more particles, so you get a positive feedback effect. Coffee inside that channel will be extracted like hell, liberating large molecules like tannins that taste astringent.
Therefore, I think that adding a paper filter as the top layer helps to prevent digging channels, and to reach higher extractions and finer grind sizes without suffering from as much channeling. I think this could be translated to the V60 too, but when I tried it the top filter immediately flowed and proved useless. I think that it's possible to do it with something that will prevent the paper from floating up, which you would put on (with the paper filter) only after the bloom phase. So I just took some pliers and steel wire and put this monstrosity together:
It fits on top of the V60 and allows to hold down the upper paper filter:
I have not tried to brew with it yet, but it will require several brews as I'll need to dial them in and see if it allows me to reach finer grind sizes without astringency. I plan to combine this with the Melodrip to really minimize any possible channel digging.
The Gabi Brewer
I recently ordered a Gabi Master A brewer that I intend to put on top of my V60 and see how much it can make my timings more consistent. I plan to re-do my repeatability experiment and see if I can be more consistent than with regular hand pours. If it's more repeatable, then I'll definitely use it to determine the effect of other variables on brew time and extraction yield.
Dan Eil's Vac60
Dan Eils recently sent me a second iteration of his 3D printed Vac60. It's a really clever device that looks like a plastic V60 but that can be sealed on top of a vacuum flask, allowing you to use suction as well as gravity and potentially grind finer. As you may have guessed from my comments above, I think this will potentially shine most when combined with the tricks above (upper paper filter and some filter retention mechanism), so I haven't yet played with it. I did make sure it fits my vacuum flask and added a small plastic part so that no brew liquid will be able to exit in the vacuum pump:
I finally received all the missing pieces to start experimenting with Büchner funnel brews. I had previously received one that had a huge upper chamber (left on the image below), which forced me to brew huge doses at a time if I wanted to have a coffee bed thick enough to avoid channeling:
With the larger upper chamber, this is what my coffee bed looked like (lol):
I also received a vacuum pump less aggressive than the one I use for vac sealing coffee. In addition to this, I received two different O rings to hold down a paper filter; one is a food-grade, circular silicon ring, the other one is a not so food-grade flat plastic ring.
The flat fits in my funnel, but just barely:
I was able to push it down all the way and it seemed to fit very well at the bottom, but it's so tight that it took me a good 2 minutes to get it out :P so I decided to first try the food-grade silicon one:
I did a first try with a poorly roasted coffee I had at my disposition and a cut out V60 (Hario tabbed) paper filter at the bottom. I set my EG-1 at grind size -0.5 (yeah, I can go slightly below 0.0) and 1500 RPM to grind a 22g dose very fine, until I could get my fingerprint to stick on the ground coffee (see my blog post about the siphon for an image). I dropped the coffee in a thermos with 1:18 water and mixed it thoroughly with a siphon paddle. I then poured it in the Büchner funnel with the vacuum pump on.
You can see a video with the end of my drawdown here. It's quite slow (as expected), and at first it looks like water is channeling around the coffee, but that's not the case so much if you look carefully from under; all the little tubes in the glass filter seem to be transporting coffee, but so little of it that it sticks to the lower surface of the glass panel and goes around it. I'm a bit puzzled as to why the coffee hangs out in the exit tube that much, but my suspicion is that surface tension at the end of the tube creates an additional obstacle.
Sadly, what I only noticed toward the end is that the silicon ring lifted. I think it's just too light to do the job properly, and next time I'll use the other one despite it being much harder to take out.
The beverage was very clear and seemed free of fines, but this definitely caused a ton of channeling. As you might guess, this first brew tasted horrible, and the extraction wasn't that high (about 22.5%), but still high for the under-developed (and baked) coffee that I used.
I suspect that the Büchner funnel and Dan Eil's Vac60 might become the high-EY equivalents of an aeropress and V60
Still Working on V60 Filters
I finished writing the codes that analyze microscope filter images and determine the image scale. I added some low-spatial frequency image filtering that removes the effects of twisted filters, and started building hole size distributions for many pictures that I took. I can already start seeing differences between filters, and a lot of differences from one location to the other within a single filter. I also noticed that my microscope can only resolve the smallest holes if I zoom all the way in, but even when I zoom out by 4x, I can almost see all hole sizes. This will definitely be super interesting, but I want to take a lot more microscope images and analyze them before I start writing that blog post. I suspect it will be my biggest one yet (that's saying something). Here are some fun images and preliminary distributions:
I also discovered that synthetic shipping foam looks TRIPPY under the microscope !
"Modding" my EG-1 Grinder
I decided to try something to limit the amount of coffee spillage with my EG-1 grinder, and it turned out great ! I used small stickers to block out some parts of the metal O-ring so that it fits the grinder chute exactly:
I also ordered a black acrylic ball which I'll try to use as a cap on my grinder entry chute. This should prevent anything undesired to fall in the grinder while keeping in with its nice style. I didn't pay this with Patreon funds because this is not for coffee science, but I'll let you know how it goes :P
My Highest Tasty V60 Extraction Yet
This morning, I reached the highest average extraction yield on a V60 yet, with Gardelli's Karimikui washed Kenyan. I prepared it at 1:17.5 (22 g dose and 331 g beverage weight) and was super surprised at the TDS: 1.52 % ! This corresponds to an average extraction yield of 22.9% with the pure percolation equation. This cup tasted absolutely stellar at this concentration, so I did not dare add any bypass water. I'll try pushing it to 1:18 next and see what happens :)
I highly suspect that some of my other recent brews with the Karimikui had the same extraction yield as they tasted similarly stellar, but if you read my earlier posts here or on Instagram you know that I was not properly re-zeroing my refractometer, so my TDS readings were all too low since a few months ago ! 🤦♂️
An Upcoming Roaster
I recently heard a really nice French coffee podcast (Café Normal) where Brûlerie du Quai, a local roaster from Gaspésie in Québec was interviewed. I was impressed by the level of knowledge from this roaster and how much he seemed to love ordering high-quality green, so I decided to place an order. You'll see these coffees eventually appear in my list of roasters when I received and taste them ! They're apparently all high-rated beans with Q grandes in the range ~87 to 91. If they're well roasted, that should be fun.
- Geisha Panama - Hacienda La Esmeralda
- Burundi Bukeye washed Bourbon
- Brazil Sitio Monte Sinai natural Catuai 44
- Rwanda Buliza washed Bourbon
Automating my Coffee Logs
Finally, I wrote a small computer code that reads up my personal coffee log (which I keep as text on my iPhone) and automatically reformats it for my Google Sheets coffee log that Geisha-tier patrons can access. This will make it much easier for me to update the log more frequently.
That's it for now, hope you enjoyed the update :)