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We've Been Wrong About Moka Pots — Transcript

by Lance Hedrick · 6,446 words · 939 segments · language en · Watch on YouTube

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0:00We've been approaching the moka pot
0:01incorrectly for decades. Some of you are
0:04like, "Shut up, Lance. My moka pots are
0:06great." That's fantastic. That doesn't
0:08mean we can't understand the moka pot a
0:10little bit better.
0:12Now, normally when people approach the
0:13moka, they think in terms of recipes.
0:16What recipe can I do to make this
0:17better? Do I go cooler water or hotter
0:19water? Do I go finer grind, coarser
0:20grind? Do I do a mound with the coffee?
0:22Or do I tamp the coffee? What size
0:24should I use? Etc., etc., etc. But,
0:27science suggests we're actually taking a
0:29different angle whenever we're
0:30approaching the moka. The moka pot is a
0:33thermodynamic relationship between
0:36pressure and heat generation versus
0:38pressure relief. So, in today's video,
0:40we're going to go over essentially in
0:42brief how the moka pot works. We're
0:44going to take a look at some of the
0:45academia that has come out about moka
0:47pots in order to help you brew a better
0:49cup. Now, I know that sounds a little
0:50bit boring, but I promise you, when you
0:52understand these thermodynamic
0:54relationships, you'll be able to
0:56approach any moka pot of any style, any
0:59size, any material, and brew a delicious
1:01moka to your flavor preferences.
1:06Now, before continuing, it is important
1:08that I mention someone who got me really
1:10obsessed with this. I made the video on
1:11the Crocapot recently. There was a
1:13commenter named Yiannis out in out in
1:15Greece, who's a physicist finishing up
1:17his PhD in astrophysics. And we've been
1:19emailing back and forth, and he sent me
1:21simulations of moka pots of different
1:24sizes with different starting temps,
1:25etc., etc. And I fell down the typical
1:27rabbit hole and found one paper
1:30specifically from 2009 by Navarini that
1:33is what we'll be using a lot of in
1:34today's video along with these
1:36simulations that Yiannis has sent over,
1:38as well as different things by Lucio,
1:40who is known as one of the moka pot
1:41legends out in Italy, Jay Pinder, which
1:44is a user on Home-Barista who's done a
1:45lot of different measurements in his
1:47moka, as well as some other things that
1:48we'll get to as we're going through the
1:50video. But, I wanted to give a shout-out
1:52to Yiannis for essentially getting me
1:54obsessed with the moka. So, the moka on
1:57its face is relatively simple. We have a
2:00pot where you unscrew the bottom
2:02and you put water right down here. Now,
2:04once this is screwed into the top and
2:06you heat it up, it obviously
2:07pressurizes. Now, what's interesting is
2:09the Bialetti was created first in 1933.
2:11On the original one, the base was a
2:13little bit more narrow and there was no
2:14pressure release valve, a little bit
2:15dangerous. And then, of course, the
2:17production stopped during World War II
2:18due to scarcity of the aluminum. Uh and
2:21then, it started again, I believe, in
2:221947,
2:23I I believe. Uh and that's when they
2:25introduced the pressure release valve as
2:27well as a wider base. But, anyway,
2:29then we have a an aluminum filter right
2:31here, which goes right on top. Now, this
2:33aluminum filter is very important. This
2:34is where water will feed up and through
2:36the basket, which has our ground coffee.
2:39Then, we have the top part, which has a
2:40little gasket as well as uh shower
2:43screen or or I guess the a basket screen
2:45is what you could say really because
2:47this is acting like the bottom of a
2:48portafilter basket. And then, we have
2:50the catch area. So, we have a tube up
2:52here, a chimney where we have the liquid
2:54that comes out and it collects in here
2:56unable to return down below.
3:00Typically, what people say happens and
3:02what I have said happened in the past is
3:04that the way this works is based off of
3:05steam pressure.
3:07That's not necessarily correct. It's
3:08also not necessarily wrong. It's just
3:11not the full picture. Now, what happens
3:13in brief during moka pot extraction is
3:15we have headspace. Now, normally,
3:18headspace is the enemy, but in moka
3:20extraction, it is the engine. I've
3:22immediately made some of the best cups
3:24of coffee I've had with moka pots based
3:27off of this understanding.
3:29So, when we pour water in, we have
3:31headspace. Let's say there's
3:3320 ml of headspace right here. Once this
3:35is a closed system and once that water
3:37starts to heat and once the metal starts
3:39to heat, the air gets hot. Hot air
3:41expands. Think about a balloon, a hot
3:43air balloon. It pushes the water down
3:46because it needs to make room for that
3:47expanding air. And that's how we
3:49initially get water coming up in the
3:51tube. This phenomenon was first really
3:54noticed, or not necessarily noticed, but
3:56first really put put out there in 2007
3:58in a paper that we'll put right here,
4:00and then it was proven in 2009 by
4:02Navarini. Now, this has also been backed
4:05up by multiple people making their own
4:06measurements, but essentially, whereas
4:09at one point, I and many others have
4:11been talking about steam pressure being
4:12the driving force behind extraction,
4:14therefore extraction has to happen above
4:16boiling, that's not necessarily what's
4:18going on. In fact, you can get coffee to
4:21extract starting at 60 or 65 C some have
4:24measured. If we have this head space,
4:27and it expands pretty rapidly, it can
4:29force water up before we even have much
4:31steam generation at all.
4:34We have water going up into the puck,
4:36but it we're continually heating it,
4:38right? Because normally people pull it
4:39off near the end, but they're letting it
4:41still go full blast as that it
4:43percolation is beginning, as that water
4:45is going through the puck and coming out
4:46of the top. So, we have a continuously
4:49heating source, but now we're depleting
4:51it of liquid in the bottom.
4:54As we're depleting liquid down here,
4:55it's getting less and less, what is also
4:57happening simultaneously? An expanding
5:00head space, which can cause a pressure
5:02dip before we're able to create or
5:04generate more of that pressure. Which
5:06means we need to generate more pressure
5:08to fill that head space in order to
5:09continually push liquid up. You
5:11necessarily have a rising temperature
5:13throughout the duration of the
5:14extraction. Now, of course, we've not
5:16yet gotten into how resistance of the
5:18puck affects this, or how anything else
5:20affects it. Right now, we're just
5:21talking about the bottom part and how
5:24extraction is actually being affected
5:25based off of the head space and the
5:27pressure generation, and from where that
5:29pressure is coming.
5:31Now, the reason I wanted to start with
5:32this is because this is a very important
5:34thing to understand when we're looking
5:37at different sizes of mokas. So, if we
5:39were to take a six-cup moka, this is an
5:41induction one, that's why it looks a
5:42little different, versus a three-cup
5:44moka, there's a huge difference in that
5:46bottom pot. Whenever we have, let's say,
5:4910 ml of water that's been displaced in
5:52this smaller moka, that's a much bigger
5:54percentage of the total volume than 10%
5:58displaced in such a big pot. So, that
6:00means we'll have a more drastic decrease
6:03in pressure and a and a higher, I guess,
6:05necessity of the heat in order to
6:08provide more pressure. So, I have less
6:10pressure drop in a bigger system than in
6:12a smaller system based off of the change
6:15of head space.
6:16The smaller the moka, the bigger the
6:18difference a small amount of liquid will
6:20have on the pressure. So, you
6:22essentially have a self-regulating moka
6:24the smaller you go. When you're at the
6:26one-cup moka, you have a much more
6:28forgiving moka pot because as liquid
6:31goes up, the pressure will actually
6:34drop. You may You won't be able to see
6:35the pressure drop, but what I'm saying
6:37is you won't be able to generate as much
6:39steam pressure because the pressure
6:41needs to equalize before continuing
6:42going. So, you actually have a lower
6:44temperature and you have lower pressure
6:46peaks due to the fact that you're
6:47displacing water that is a bigger amount
6:49of that head space, which will then need
6:51to be subsequently fit filled in order
6:53for pressure to continue generating.
6:55Now, the pressure will not be as
6:57affected in a three-cup as it is in a
7:00one-cup because it's a much smaller
7:01percentage that is left. And the same
7:04way for a six-cup and up to a 10-cup.
7:06The bigger you go, the smaller of an
7:08effect it'll have, the more your steam
7:10generation will be left unperturbed. In
7:13much bigger mokas, you will end with a
7:15much higher temperature and a much
7:16higher pressure at the end of your
7:18extraction than in a smaller moka, all
7:21things held equal. Now, we're at the end
7:23of the video and just really quickly, if
7:26you enjoy this video on this deep dive
7:28on moka. By the way, I'm getting I'm I'm
7:29so into the rabbit hole on moka it's not
7:31even funny, but I'm considering buying
7:32all these architecturally important
7:35design, you know, two,
7:37three-hundred-dollar moka pots in order
7:38to make a crazy videos on mokas. If that
7:39is something you're interested in based
7:41off of like watching this video and
7:42enjoying the more, I guess you could say
7:44deep dive approach to these things, the
7:46the way I like to do things, please let
7:47me know by hitting the like, hitting the
7:49subscribe, maybe leaving a comment down
7:50below, and we'll go as far into moka pot
7:52lore and history and science and
7:55technique as you all want because it has
7:57been a ball of fun, and it gives me more
8:00justification for this dope tattoo that
8:01I got from my friend Mix Wires in
8:02Australia. But anyway, thank you for
8:04watching. Please hit that like and
8:05subscribe. Helps the channel, helps me,
8:06and helps these videos. Let's continue
8:08on with our moka deep dive.
8:13Now, the question becomes less of how do
8:15we scale a recipe from a one pot to a
8:17three pot to a six pot and more a
8:19question of how do we make a recipe for
8:22one pot, a three pot, and a six pot?
8:25This isn't the same brewer at different
8:26sizes. It is a family of very
8:29fundamentally different brewers based
8:31off of how each one handles pressure
8:34with the release of liquid.
8:36We're essentially working on this
8:38dynamic between pressure and heat
8:40generation versus pressure relief. So,
8:42in a tiny moka, we have a much more
8:44intensive pressure relief based off of
8:47the bigger difference there is when you
8:49have liquid release.
8:51Extraction is effectively an energy
8:54sink. As liquid's going up, it is
8:57actually causing the need for
8:58regeneration of that pressure because we
9:01were gaining head space, which means we
9:03need to generate more of that pressure.
9:04The one cup can be seen as like an air
9:06expansion brewer. The three cup can be
9:08seen as like a mix expansion between
9:10steam and air, whereas the six cup and
9:11up are largely based off of steam
9:13pressure due to the less effect the
9:16lessening effect with the bigger you go
9:19of the difference on head space based
9:21off of this displacement of liquid.
9:24One of the big fears people have in moka
9:26pot brewing is brewing with over 100°
9:29water, which does happen, just never
9:31initially. Now, one way that we can and
9:33the most important way that we can
9:35manipulate the temperature of the water
9:37during and at the end of extraction is
9:39based off the fill level before we
9:41start. The higher your fill level up to
9:43the valve, the hotter the brewing
9:45temperature becomes. The lower amount of
9:48water, the cooler the brew will begin
9:50and the cooler the brew will end. The
9:53more amount of water, the hotter it will
9:55begin, the hotter the brew will end. So,
9:57if you're wanting to slightly lessen the
10:00temperature of your extract, you can
10:01always lower the water level in your
10:03moka pot. The issue is then you will
10:05also affect the concentration. Less
10:07water means a smaller ratio, means a
10:09little less extraction, and a higher
10:11concentration in the final cup. That
10:13said, I think it's a pretty good
10:15trade-off when you're getting that
10:16really intense bitterness that can come
10:18from that late stage extraction when
10:19you're using too much water. All we're
10:21doing with the water level is another
10:23way to manipulate pressure relief versus
10:26pressure and heat generation. Now,
10:28another way is the temperature of our
10:30water when we first put it in. Now,
10:32there have been recommendations to use
10:34boiling water because we don't want the
10:36cake to sit in here getting burned. And
10:38then there are, you know, Italians who
10:39say use room temperature water.
10:42In this situation, it turns out the
10:43Italians were correct. When you use room
10:45temperature water, you actually begin
10:47your extraction at a much cooler
10:48temperature, and again, you end at a
10:49much cooler temperature. When you start
10:51with boiling water, you are absolutely
10:53going to be extracting at over 100° C
10:56before the end of the extraction. So,
10:58then the question comes down to, well,
10:59what about the burning cake of coffee?
11:02There's no real evidence that that is
11:03actually causing a deterioration of
11:05flavor. Yes, you're likely losing some
11:08volatile aromatics, but that cake is
11:10actually getting saturated, getting
11:12wetted pretty early on, and so it's just
11:14kind of sitting there at like a bloom
11:15phase with a hot water. So, in
11:17pour-overs, we bloom with 100° C, 95° C,
11:2190° C water, and we let it sit for 30
11:24seconds, a minute, 2 minutes sometimes.
11:27Essentially, you're wetting those coffee
11:28grounds relatively early due to the
11:30expansion of air, and it just takes a
11:33while to build enough pressure to fully
11:34release up into that top part. We're not
11:37actually needing to worry too much about
11:39burning the cake, so to speak, or losing
11:41too many volatiles that way. The
11:43question is more so what has a worse
11:45impact on taste? Potentially letting the
11:48coffee sit at 70 80° prior to being
11:50fully soaked with hotter water and
11:52extraction beginning, or allowing the
11:55end of the extraction when the puck is
11:56the most vulnerable,
11:58a potentially way over extracting with a
12:00lot of channeling and with essentially
12:02the Strombolian effect we'll get into in
12:03a second, where we have gurgling water
12:05going through the pot because how hot we
12:07hit and how quickly we're depleting the
12:08water with the higher pressure and the
12:09higher flow rate, etc. etc.
12:12Do two mokas, one with room temperature
12:14water, one with boiling water, and see
12:16which one tastes better. Now, of course,
12:18you're not able to isolate variables to
12:20see if one was tasting better due to it
12:23having, you know, a fresher puck that
12:25wasn't sitting on exposed heat versus
12:27one that had the more intense late later
12:29stage extraction, but that doesn't
12:31matter as much as long as you're getting
12:32a good cup.
12:34Just like an espresso, in order to
12:36generate pressure, we have to have input
12:38flow, so the water going up that tube,
12:40and we need to have resistance. Now,
12:41resistance, obviously, we have some
12:43based off of this being closed off and
12:45we have just a little tube, but that
12:48tube is still a pressure release. So,
12:50the main part of resistance that we're
12:52giving this system is the puck of
12:54coffee. So, you can increase that
12:56resistance or decrease that resistance.
12:58You can open up the system a bit more or
13:00close it down a bit more. Now, we
13:02consider this a closed system because we
13:04are generating pressure due to the
13:06difficulty of water getting through this
13:08packed down or this, you know, filled
13:10basket. So, what we need to understand
13:12now is the grind size and the dose. The
13:14dose should always be to the very top of
13:17your basket. Now, if you want to put a
13:19mound, whatever, and when you push it
13:21down, it's going to actually push sit
13:23flush against that basket, which is
13:24fine. There's no issue with sitting
13:26flush against the basket. Think about an
13:28espresso machine. We do have it sitting
13:30flush against that basket. If it's going
13:31through a medium the whole way until
13:33contact with the screen, then we're not
13:35going to have this little vacuous area
13:37where it's going to need to have extra
13:39energy to travel upward in a space of
13:41nothing. This is why people have noticed
13:43when they underfill their basket, they
13:45get a much more bubbly and gurgly
13:47experience coming out of the chamber. It
13:50has to really experience that it has to
13:52really push for that pressure
13:53differential in order to shoot up the
13:55chamber. Always fill your basket. So,
13:57that's another reason why you need to
13:58understand which moka to get. But then
14:00again, if you don't like bitterness, if
14:02you don't like high brew extractions,
14:03but you want a ton of coffee, you may be
14:05better off using a one cup and brewing
14:07it a couple of times. Or you have to be
14:09okay with using much coarser grounds on
14:11a bigger moka, which will make sense
14:12here in a bit. Obviously, the finer you
14:15grind, the more closed that system's
14:17going to be. The more pressure is going
14:18to be built. The harder it is for the
14:20liquid to get through.
14:22The finer you go, the hotter that
14:24brewing temperature is going to be,
14:26period. The coarser you go, the cooler
14:28that brewing temperature is going to be.
14:30We do need the grounds to act as a seal
14:33for the system to an extent. It's a
14:35permeable seal, sure, but it's a seal
14:37nonetheless. And when we go too
14:39coarsely, we can have essentially
14:41boiling water going through it because
14:43it's not able to have a specific
14:44threshold that pressure can give it.
14:46When you have pressure in a system, the
14:48boiling point can be higher. You can
14:50retain liquid water at higher
14:52temperatures. Does that make sense?
14:54Think of a pressure cooker. When you're
14:55under pressure, water can maintain its
14:57liquid form at 110° C.
15:00Think On the opposite side, if you're at
15:03altitude, water can boil at 90° due to
15:05less pressure being so high in the air.
15:08If you go too coarse, you're not going
15:10to allow for that pressure cap, and
15:11you're going to have boiling water
15:13that's going to be coming out,
15:16and it's going to taste gross.
15:18Tamping, if you're going too coarse, or
15:20if you grind up and you realize you're
15:21too coarse, tamping can actually help
15:23give you some of that pressure back,
15:25especially if you do some sort of
15:26nutation or something to pack it down.
15:28But, that's only if you go insanely
15:30coarse. If you're on the finer side, or
15:31using a spoon to press it down, can
15:33absolutely ruin your cup. And it's
15:35because, again, you're giving more
15:36pressure and more temperature. The
15:37darker the roast, the lower the
15:39temperature it actually wants. So, if
15:41you're giving more pressure, more
15:42resistance, which will give you more
15:44pressure, you're also getting more
15:45temperature. More temperature, acrid,
15:47gross, bitter, burnt we don't want that.
15:50We want it level. We don't want to go
15:52too fine cuz we're trying to relieve
15:54pressure, and we don't want to go too
15:56coarse because we need a little bit of
15:57pressure in order to not have just boil
15:59bubbly water coming out of our spout.
16:02I do enjoy putting an Aeropress filter
16:04right here. This is largely though to
16:06clean up the cup and it helps with
16:08extraction efficiency because it's
16:09opening up more surface area for the
16:11liquid to flow out. Uh but, that's
16:13obviously something that you can decide
16:15upon. Now, there is a way that you can
16:17actually change hydraulic resistance.
16:19And Aeropress filter paper is not
16:21necessarily going to increase hydraulic
16:23resistance. In fact, it could be argued
16:25it's reducing it. This This has been
16:27shown with with espresso, for instance.
16:30There are certain papers that can help
16:31to speed up extraction. But, there are
16:34papers you could use if you wanted to go
16:36even coarser on your grounds while not
16:38having that bubbly effect from going too
16:40coarse and breaking the pressure seal.
16:41You could use thicker paper filters like
16:43Allströms or like High Flux or something
16:46along those lines in order to generate a
16:48back pressure that doesn't rely upon the
16:50grounds in themselves.
16:53So, during our extraction, flow is
16:55relieving pressure. As the flow rate is
16:57coming out, and as it's increasing,
16:59we're relieving pressure in the moka pot
17:00behind, which is also going to allow for
17:03an increase of temperature, or force an
17:05increase of temperature, to continue
17:06that expansion upwards. Now,
17:08interestingly in that original Navarani
17:10paper, there was a a model showing that
17:13permeability decreases throughout
17:14extraction. But, I think that's not
17:16necessarily accurate. I think we know
17:18from espresso that unless you're using a
17:20really high fines-producing grinder and
17:21a really darkly roasted coffee,
17:23permeability is actually the opposite of
17:25what he proposes. And I find the same to
17:27be true in a moka pot. As you continue
17:29to extract your solubles and you extract
17:32different parts of the coffee, your puck
17:33is effectively less strong near the end
17:36of the extraction. Unless there's a ton
17:38of fines, you have fines migration
17:39blocking the screen itself. But, that's
17:41not really the case with modern grinders
17:43and lighter roasted coffees or even dark
17:45roasted with a decent grinder. The
17:48permeability is going up throughout the
17:50extraction, which is allowing for a
17:51faster and faster flow rate, which means
17:53that we're going to have a faster and
17:54faster depleting base, which means we're
17:56going to have to have the water
17:58increasing in temperature more and more
17:59heavily in order to continue to keep up.
18:02With the decrease of pressure, you have
18:04a lower boiling point. Whenever you're
18:07increasing your pressure in a much
18:08bigger moka, your boiling point goes up
18:10higher and higher. That's why we're able
18:12to have a stream of liquid coming out
18:15even at 110° C of water because it's not
18:18boiling as it's going through the puck.
18:21Now, something we haven't mentioned at
18:22this point is the differential or the
18:24gradient throughout the puck during
18:26extraction. This is something that needs
18:28to be understood as well.
18:30At the very bottom of our puck, it's
18:32experiencing by far the most pressure as
18:34well as the most temperature. As it
18:36moves up, it greatly reduces. So, at the
18:38bottom at some point during extraction,
18:40it could be experiencing one, two, two
18:43and a half bar of pressure depending on
18:45how finely you're grinding and how much
18:47liquid you have in the bottom. But, up
18:48near the top of it, you're almost at
18:51zero relative to the brewing overall the
18:54brewing. So, the release happens once
18:56the it's it's outside of atmospheric
18:58pressure, right? So, as it's building
19:00and it's outside the atmospheric
19:01pressure, we are building pressure. The
19:03lower part of it is experiencing the
19:04most. As you go up and that the strength
19:08of the puck is not as much as you
19:09continue to go up, you are experiencing
19:12a massive pressure drop from the bottom
19:14to the top of that puck, as well as a
19:17temperature differential that can be
19:19quite extreme from the bottom to the top
19:21of the puck. And even as it's going up
19:23higher, you're losing more and more
19:25temp, and that's why as it comes out, it
19:27you may measure initially 50 and end at
19:2870° inside the actual chamber itself.
19:32Now, I'm going to be brewing a really
19:34lightly roasted coffee, but you can do a
19:36dark roasted coffee using the same
19:38principles. In fact, the way I approach
19:40light roast is the way that most of you
19:42should probably approach dark roasts. I
19:44enjoy lower extraction with lighter
19:46roasted coffees, around 16, 17, maybe
19:4818%, and I like my TDS with this to be
19:51around 4 or 5% TDS. I find that to be
19:55fantastic. Now, the way I'm able to
19:56achieve that is with quite coarsely
19:58ground coffee and a little smaller ratio
20:00because I want to use less water in this
20:03in order to not have as high of a
20:04temperature.
20:07Essentially, I'm going to do 120 g of
20:09room temperature, I guess it's a little
20:10cooler than room temp, water inside of
20:12the base. So, I'm going to actually
20:14weigh it. What you can do is, you know,
20:15you can see if there's a line on the
20:17inside to be more consistent so you
20:18don't have to use a scale every time,
20:20but for now, I'm just going to use a
20:21scale. We're going to put this on, and
20:23I'll weigh out
20:25120 g of what I have as treated water.
20:31Maybe just remember roughly the the
20:33level, but I do not like filling up all
20:34the way the steam valve. I've noticed
20:36that it is just doesn't taste as good.
20:38We get too hot of a temperature near the
20:39end, and there is a drastic difference
20:41as we showed in those graphs earlier
20:43between filling up even 30 ml below that
20:46fill level. You go even lower, you'll
20:47get an even lower temperature during the
20:49puck, but this is a nice um
20:51a nice amount of liquid for the
20:53extraction I'm doing, which is going to
20:55be roughly a 1:3, very similar to
20:57espresso. This is essentially like a low
20:59flow soup shot for those of you in the
21:01know. Uh you can't really replicate
21:03{quote} {unquote} soup. For those of you
21:04that don't know what I'm I'm about, you
21:05can go either ignore or check out the
21:07videos, but it's hard to replicate
21:08because you're not able to get the same
21:10flow rate. The max flow rate you're
21:11really getting through a moka is like 2
21:132 and 1/2 ml a second. Whereas soup, you
21:15kind of want 5 to 6 ml a second ideally.
21:18But anyway, we've got 120 g in here.
21:21Feel free to copy this at home if you
21:22want with a three cup, though I think
21:24one cup is your best bet. It's the most
21:25forgiving and makes the tastiest in my
21:27opinion. But we'll do three cup because
21:28it is objectively the most used one in
21:30the world, that and the six cup. Uh by
21:32the way, fun fact, over 104 million moka
21:35pots had been sold by 2009 when now
21:38Vergnano wrote his paper and about 4
21:40million a year were being produced by
21:41Bialetti specifically uh during that
21:43time. The amount of mokas around the
21:44world is insane. It's actually how
21:45coffee went from Italy over to places in
21:47South America as post World War II when
21:49a lot of Italians left. Moka was brought
21:51over there and it's all over South
21:53America based off of that and has been
21:54expanding for 80 years around the world.
21:56Absolutely insane how many people have
21:58mokas. But anyway,
21:59120 g in there. Now I've got ground up
22:0223 g of coffee. Yes, in a three cup I
22:05get 23 g in there and it's because we
22:07need to ensure that we're fully filling
22:09that basket. So what I like to do just
22:11to ensure of the amount I have if I'm
22:12trying to be consistent is I'll weigh
22:14it, but again you don't need to do that.
22:16I'm using a funnel that is actually for
22:19an espresso uh basket, but you know,
22:21c'est la vie. We're going to give it a
22:22shake and then I am going to just tap it
22:24just to ensure I don't lose it. But I'm
22:26not going to do much more of
22:28other than that because again, I do not
22:30want to have too much resistance in that
22:33puck. And we also know from espresso
22:35testing that mounting in the center is
22:37actually a preferred way for extraction.
22:39So we're going to drop that into our
22:40water. Boom. Now I'm going to prepare my
22:43Aeropress filter. Now this is very
22:45simple. This cleans up the cup. You
22:46don't have to do this. People fear that
22:48it's going to disallow oils from getting
22:50through. Maybe it cleans up a little bit
22:52of it, but overall you will get a more
22:53consistent extraction doing something
22:55like this. And it's very easy. You just
22:56toss the filter on and it fits perfectly
22:58on a three cup. I do do squirts with a
23:00little squirt bottle or you can just,
23:02you know, take a spoon and just dribble
23:04a couple of drops of water on it, and
23:06then essentially just smash it into
23:08place, and you're good to go. Make sure
23:10you're tight, because you don't want to
23:11an explosion.
23:13Boom.
23:15And now we begin. Now, I'm going to do
23:17this at uh the level three, that's about
23:19450
23:22W or so, I believe. So, that's what
23:24we're going to do. That's not obviously
23:25realized inside, that's what the
23:27induction plate is actually giving off,
23:28and then we have this little stainless
23:30steel plate. Now, with this, it takes
23:31normally around 4 minutes. So, let's
23:34talk about what is happening inside to
23:35see if we understand all of the thermo-
23:37thermodynamics. We put room temperature
23:40water in, maybe slightly cooler than
23:41room temperature water inside, but we
23:43have closed off the system by giving it
23:45finally ground coffees, not really that
23:47fine, but still it's a pretty deep puck
23:49on top of it. So, it's essentially a lid
23:51on the system itself, and we screwed it
23:52together, so that the only exit are
23:54through these little apertures in the
23:56tubes. Immediately, we have an expansion
23:58of air, but air isn't going to be able
24:00to get up and out. It's stuck inside
24:02that bottom bit, because the tube itself
24:04is submerged, so that air really has
24:06nowhere to go. It's impossible. There is
24:08no outlet for the air. It's at the top,
24:11because it is less dense than the water,
24:13obviously. It is in a gaseous state, and
24:15so there's nowhere for it to go. It
24:16can't somehow get through the water, so
24:18instead it begins to expand, and that
24:19water has nowhere to go. So, as it it is
24:22expanding, where does it go? It can't
24:24become smaller, it begins to go up the
24:26tube. Some of it obviously volatilizes
24:28into steam, but a lot of it is going up
24:30that tube, which happens pretty
24:32initially, pretty instantaneously. And
24:34again, if we were able to look at a
24:36cross-section of this as it's
24:37extracting, we'd have liquid already
24:39going up the tube right now, potentially
24:41getting the bottom of that puck somewhat
24:43wet already.
24:45So, we don't have dry ground sitting in
24:46there getting really hot, getting licked
24:48by the heat. In fact, this very top,
24:49which oops, I normally have the pot open
24:51the whole time, but I've been talking
24:52and forgetting. So, let's get this
24:54centered. There we go. The top part is
24:56not actually hot right now. The down
24:58here, not very hot. It's down here where
25:00the heat is obviously rapidly expanding.
25:02So,
25:04if we were to look at a cross section,
25:05we'd see the puck is already probably
25:07halfway wet if not saturating even more
25:09all the way up. It just takes a little
25:11bit longer for it to come all the way
25:12through. Now, we're at about 2 minutes,
25:14so we're halfway through the breaking
25:15point of when the liquid should actually
25:17come through the top part of this where
25:19we're going to have kind of a release.
25:20If we recall, we have a displacement of
25:22liquid, we have an expanding amount of
25:24head space, and due that we have a drop
25:27in energy essentially. So, we have to
25:28make up that energy somehow. The way
25:30that we're doing that is continuously
25:31heating up that base. So, we continue to
25:33heat it up. Steam pressure tries to
25:35start building, but as pressure
25:36continues to dip due to the displacement
25:38of water, it's difficult for it to
25:40retain its force and its expansion
25:42efforts. Now, the bigger you go with
25:44your moka, the easier it is for it to
25:45maintain and to build on top of what it
25:48was. The smaller it is, the more
25:49difficult. As I said earlier, a three
25:51cup is more so like a mixture between
25:53this hot air expansion and steam
25:55creation. Whereas, when you get a little
25:57bit bigger up to that six cup, it's
25:58largely steam pressure that is a forcing
26:00this extraction.
26:02When we get down to that one cup again,
26:03it's largely just that hot hot air kind
26:05of self-regulating it. But anyway, we're
26:07at about that 3-minute mark. We should
26:09have liquid really start to be moving
26:11through this. We are having a lot of
26:12displacement going on, and there we go.
26:14Actually, we have it starting to come
26:15out now. With this coffee, it was
26:16earlier than a previous coffee. I'm
26:18going to go and drop it down to one and
26:20let it continue going. And then when we
26:22have it at about uh about 50-60%
26:26I may go and just lift it a little bit
26:27because I see it starting to want to
26:29bubble a little bit, which means we're
26:30getting the temperature pretty hot. And
26:32honestly, I might just stop it right
26:34now.
26:36Unless it really starts to flow that
26:37slow down the flow. We're just going to
26:39let it sit here and run. Let it run a
26:41little bit longer. I'm going to give it
26:42just a touch more heat.
26:45Let it sit for a couple seconds.
26:47And there. Now, we're going to be done
26:49with this. I'm going to turn that off
26:50and just let it finish out.
26:52So, there we have our moka pot. Now,
26:54again, I don't like it to get to the
26:55very end with the Strombolian effect.
26:57That's where we have it spluttering
26:58everywhere. I'm going to let it go until
27:00it's finished, and that residual
27:01pressure should be more than enough to
27:03get all the liquid out prior to that
27:05effect happening. So, once it hits that
27:08air gap because we're not still applying
27:10heat, we should be able to stop a lot of
27:11that from happening. So, you saw there
27:12was some of that foam where it wanted to
27:14start doing it, but we don't have enough
27:16pressure or temperature down there to
27:17allow it to actually complete that
27:19cycle.
27:21All right. So, now we're finished. We
27:23can close this lid. We immediately
27:30pour it out.
27:31Now, normally what I aim for on the
27:33yield with this amount of liquid in
27:34there is about 70 g.
27:36And we're sitting at 71. There's a
27:38little bit of dribbles left. 72. So,
27:40around 70-72 g seems about right.
27:44And now, for fun, we'll just take a
27:45quick reading of this. So, we put 23 g
27:48in. We have 72 yield.
27:50This was probably brewed at around half
27:52a bar of pressure, maybe less than that,
27:54and we got a 6.03% TDS, which with a
27:5823-g dose, that is giving us an
28:00extraction yield of almost 19%. It's
28:0318.88.
28:05So, obviously, you could go higher if we
28:06went finer on the grounds. If we did a
28:08higher level or or more yield
28:10essentially would also get us up to like
28:1120% extraction. Or if we wanted to do
28:14all these different variables we've
28:15talked about in the video, but with all
28:17that being said, let's take a sip of
28:19this.
28:20>> [snorts]
28:30>> Hugo hates moka pots, by the way.
28:33>> I like it.
28:34>> I know you do.
28:35>> It's freaking good.
28:37It's a 7.3
28:40>> 7.3?
28:41>> 7.33
28:43>> [snorts]
28:45>> Which I don't think is that high. I
28:46think that's really good.
28:47>> [sighs and gasps]
28:48>> And [snorts] our sip.
28:52The finish on that so perfumy.
28:54Six.
28:57Dang it.
29:03With a moka pot, it's very difficult
29:05since you can't control the liquid going
29:07through it other than with temperature
29:09to go even coarser than what we did
29:10there. We could probably get away with a
29:12few notches coarser, but you go too
29:14coarse and you're going to break that
29:15seal and you're going to have bubbly
29:16water coming through it and causing
29:17crazy turbulence and weird accurate
29:19extractions. But, with a dark roast of
29:22coffee, this is also going to be great
29:23and it's something you can use as a base
29:24for your milk drinks and things like
29:26that.
29:28Now, I think there have been a lot of
29:29incredible videos out there and I want
29:31to give some special shouts out largely
29:33to my friend Matteo who is an Italian
29:35Brewers Cup Champion, is a phenomenal
29:38coffee professional, and has the best
29:40videos I think on YouTube on the moka
29:42pot themselves. And he has come to a lot
29:44of these conclusions, so I'm not sure
29:46with the kind of physical and and
29:47thermodynamic explanations with them.
29:50But, he has shown a lot of this in his
29:52own videos which I think are fantastic.
29:54And then you have people like I've
29:55pointed out on the Home Barista the
29:57forum, my friend who's finishing his PhD
29:59in astrophysics, Jonas, and a few others
30:01who have done these tests over the
30:03years, as well as the papers that I've
30:05been referencing. This is something that
30:08has been noticed and has been studied
30:09and has been talked about for a while.
30:12And in fact, even though there are
30:13people like my friend Matteo saying use
30:15room temperature water, saying use less
30:16water, or whatever for the temperature,
30:18people still will call it into question
30:20cuz there's no proof. Well, we now have
30:22proof. And hopefully I've shown you more
30:24than enough proof and the papers are
30:25linked down below and you can go look.
30:27Hopefully this was enough for you to
30:28really understand the moka pot, to have
30:30a full scientific grounding in your
30:32approaches. So, when you go to something
30:33like the Venus, which is a completely
30:35different shape, completely different
30:36base, completely different generation of
30:38pressure, you're going to be able to get
30:40on that, dial it in to your taste
30:42preferences using the thermodynamic
30:44principles shared with you today on
30:46pressure and heat generation versus
30:48pressure relief. Thank you so much for
30:50watching. Most importantly, I hope that
30:52you brew something tasty today. And
30:54cheers.

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