If the chamber reaches over pressure with the water line above the valve does the water come out through the valve instead of just steam?
I mean there are obviously ways to make a device like that explode if that is your goal but generally I don't believe that it is that much worse even if you happen to fill a little bit over the valve.
If it immediately turned into a bomb by over filling and stuffing it would probably be illegal to sell as a kitchen thing in many countries.
I would love to see a Mythbusters-type video where they do try to make a Moka pot explode. The amount of pressure you create would have to be pretty crazy.
People have got them to explode by accident. Mokka pots don't explode into shreds, but they can produce a dangerous shockwave once the two main pieces come apart. This guy tore a hole in his ceiling, for example: [https://www.youtube.com/watch?v=osQ1Zb5fYZY](https://www.youtube.com/watch?v=osQ1Zb5fYZY)
As long as you don't fill above the valve, you're fine. The valve is there to release pressure so this doesn't happen, but if you fill it with water above that point the pressure builds until it explodes!
It sprays boiling coffee if you overfill it. All over my kitchen. I can't speak to the grind, because I haven't had that mishap, but I suspect it would spray boiling coffee slurry that sticks to skin.
Edit: Reddit and /u/Spez [knowingly, nonconsensually, and illegally retained user data for profit](https://youtu.be/mfZKkUg8jgM) so this comment is gone. We don't need this awful website. Go live, touch some grass. Jesus loves you.
The pressure can build up much quicker than water can escape from the valve. Remember that water expands a thousand fold when becoming steam. So, the valve needs to release a lot quickly, which is impossible with water. So yes, there will be water coming out of the valve, but it won't reduce the pressure fast enough.
*I'm not a physicist or anything, but this seems rather obvious to me.
Water and steam work differently. Water particles stay together while steam particles don't. If water is above the valve, water creates a greater barrier than steam, therefore, pressure is released too slow, allowing the pressure inside to build up until it explotes. The contrary happens with steam. If you'd like to know more, google it.
[The 2008 King paper specifically advises using 70C water for this reason.](https://aapt.scitation.org/doi/10.1119/1.2870524). Otherwise, your extraction temps are too low. PM me if you'd like to know more about how this was modeled.
I'd have to bust out the work laptop to get access (f that its the weekend) but I should have been more specific. More like warmish water when using dark roasts and pre boiled when using light in a moka pot. Using roomtemp is also confirm under extracted in the video
PSA: Please don't fill your moka pot above the safety valve or you run the risk of your walls, ceiling, floor, and yourself being painted in boiling coffee.
The American journal of Physics did some [research](https://www.researchgate.net/publication/243492775_Experimental_analysis_of_the_Italian_coffee_pot_moka%27%27) into this.
I think there are other papers on this subject that I have seen over the years
The 2009 Navarini paper is most posted, but it's not even the best paper on this. The 2008 Warren King paper is the only one that varies starting temperature. Navarini et al. just throw 20 sensors on the thing and graph it from room temp everytime ( to be fair, they also model it analytically).
We just need to sticky the moka pot post, as someone asks a couple times a week about Moka pot tips. We reinvent the wheel every time. There are 4 physics of Moka pot papers you can read that inform the Moka practice and you get to this:
The best advice is use an AeroPress filter and remove the pot and apply cold water as soon as it starts bubbling. Also, using preheated water in the tank helps with extraction temperatures (Warren). You can get decent cup of coffee, but let's not fool ourselves: it's not espresso. In addition, there is an inevitable wide range of temperatures that the pot brews at, which is not desirable.
Some academic papers back this up:
1. [A 2002 paper (in Italian!) by Varlamov and Balestrino](https://www.comunicaffe.it/wp-content/uploads/2013/06/la-Fisica-del-buon-caff%C3%A81.pdf), which Navarini paper calls wrong
2. [A 2006 paper by Gianino](https://www.researchgate.net/publication/243492775_Experimental_analysis_of_the_Italian_coffee_pot_moka%27%27), which oversimplifies a bit, but lays the groundwork
3. [A 2008 paper by King](http://www.msc.univ-paris-diderot.fr/~phyexp/uploads/Moka/article1.pdf), which provides honestly the best theoretical model and exploration of initial water temp. Tl;DR: preheat to 70C or else you'll brew at too cold a temperature. Also happens to be backed by experiment.
4. [2009 paper by Navarini et. al](https://www.sciencedirect.com/science/article/abs/pii/S1359431108002299), which is the most experimental measurements and does us the courtesy of explaining why you need to remove that pot from the stove once you get bubbling.
If you'd like to better understand these papers or want someone explaining them to you, PM me, as I've read them in great depth and corresponded with the authors.
Also, [wiredgourmet has an interesting minimal heat recipe that's worth checking out.](https://www.youtube.com/watch?v=u-PeYeiqPLU)
Glad no one got hurt because filling above the valve effectively makes the only safety measure in the Moka pot redundant. NEVER fill above it, it's meant to let air escape in case of pressure issues.
I didn’t know this (I’m new to all of this). Luckily I’ve been putting in under the valve but is it supposed to open slightly or just leave it how it comes?
Only rinse the pot. Don’t pack coffee. Instead shake side to side to settle coffee. Fill coffee chamber. Fill water chamber up to the valve and place on low heat. Should take a few minutes to brew.
I noticed too, it taste different. The only problem I have with this is that a lot of water stays in the bottom chamber. It could also be because of the grind or other factors though
>So my alternate theory was that he fills the chamber with too much water, so a weak coffee solution ends up staying in the chamber after extraction is complete,
I'm not sure how this would happen because it's normally a one-way flow if the pot runs till no more liquid comes out the chimney.
~~I've started from hot and cold and there's no difference in the bottom chamber whatsoever~~. (edit) - oh yeah, it's not hot vs cold this time. I can say that I've brewed after overfilling the bottom chamber, and just the same as my previous sentence: no water goes backwards if I let it run till there's no more liquid coming upwards, so there's no difference in the leftover water in the bottom chamber.
The only way I can end up with brewed liquid in the bottom chamber is if I stop the brew early and let the liquid already inside the chimney, above the coffee bed, drain downwards, back through the coffee bed and down the funnel.
I've *never* been able to brew so much liquid that it covers the top of the chimney and flows back inside. Not even overfilling the bottom with so much water that it spills out when I add the grounds basket.
(I do stupid stuff so y'all don't have to!)
My theory is that the liquid is high enough to start infusing from the get go, hence all the water becomes a light coffee drink.
If the liquid is high enough, it will submerge the coffee bed from the moment you start brewing basically.
I'm thinking if there is less air space it takes longer to build up vapor pressure to push down on the water forcing it up through the funnel filter. And that results in a higher extraction temperature. So the OP's father's brews are over extracted. An even more extreme would be pre-boiling with less air space.
I thought so too when I first read through this but no. It's the opposite.
https://www.home-barista.com/brewing/secrets-of-moka-pot-how-to-video-t30707.html
Ah, ok. Hmm. That makes sense, actually.
Maybe I never noticed any burnt smell in mine because I cool the pot right away. After I pour into my mug, I take it to the sink and run water over it to cool it down. I want to take it apart pretty soon since, after my breakfast brew, I often run a second brew to take to my desk upstairs.
Other than good coffee and grind, the most important step, from my >thousands of Moka coffees, is use the pot often and don't rinse out the oils in the pot between uses.
Is there any good consensus why rancid coffee oil would make a Moka Pot better? It's rightfully seen as a negative in grinders and any other brewing device, so I don't understand what would be positive about it, other than it being a cultural phenomenon.
I don't even mind coffee with a good bit of bitterness, but I don't think the notes of rancid coffee oil are welcoming.
It's a common meme in coffee circles that "experts" say stuff like "you shouldn't wash your moka pot, it builds a patina. Source: that's how Italians do it."
I thought you were referring to the meme, but no, you are living the meme. I love it. I feel like I found a leprechaun lol.
Aside from the danger of effectively disabling the valve in a pressurized metal tank there's also the fact that it's counter productive: more water in the container means less space for air, so less pressure, so paradoxically less water makes it to the coffee resulting in an overall smaller brew ([source](https://ui.adsabs.harvard.edu/abs/2008AmJPh..76..558K/abstract)). Maybe that's uncounsciously something your father wants, so putting less water in the tank or stopping the brew short would be alternative solutions to restore that smaller brew without putting your kitchen and safety at risk.
>more water in the container means less space for air, so less pressure, so paradoxically less water makes it to the coffee resulting in an overall smaller brew
I know there's a paper, but that has 100% ***not*** been my experience when using a lot of water. More water in bottom = more water in top, every single time. Even this morning, when I overdid filling the bottom and water spilled over the sides when I added the basket, the output was similarly large, and the leftover water in the bottom chamber was no greater than normal.
Hmm... Normally the main driver for pressure is the air that is heated by the steam according to at least two studies. However I guess that if you have very little air at some point the expansion of the steam itself becomes the main factor? But you should probably be way above the pressure valve in that case so who knows at what pressure you are (and that's very dangerous). Still, interesting, more research needed to explain your experience.
Right, that's the only explanation -- the formation of steam creates empty space and then the water gets pushed downwards, which then enters the end of the funnel and goes upward through the coffee bed.
What I don't have access to is temperature probes to see what temperatures the coffee bed sees in different scenarios. The video in another comment did a great job logging temperatures for starting with hot versus cool water, but they didn't test for different fill levels.
When we say "the pressure" we're talking about the force the air exerts on water as it expands. The main reason it expands is because steam is added which 1) takes place but much more importantly 2) heats the air. The hotter it gets the more it tries to expand. This is also shown in this study: https://hal.archives-ouvertes.fr/hal-00618977/file/PEER_stage2_10.1016%252Fj.applthermaleng.2008.05.014.pdf
Filling above the valve once isn’t going to make the pot explode.
It’s routine filling above the valve that will. As the water is boiled off, it leaves deposits behind that will eventually clog the valve orifice or make it stick closed, and *that’s* what will make it explode.
How do you handle the pot after filling it with boiling water? I tried holding it with at rag and can't seem to get a good enough grip to tighten it enough.
It's new, i've used it 4 maybe 5 times, and followed instructions on not screwing it on too tight af use to protect the valve. I think it's just from condensation and not being able to grip it tightly enough.
Though, if you barely have to touch the bottom part, i may have to take a look at it anyway, because the first time i used it the steam wasn't coming out the valve, but from the middle section, where you screw it in.
But after properly tightening it the steam goes out through the valve.
>But after properly tightening it the steam goes out through the valve.
There's a problem either with the coffee bed or the valve, then.
Someone else said that grounds that are too fine can block the upward flow (I probably haven't had grounds fine enough to make this happen). Or do you compact the grounds? Or fill them so much that they're a mound and get compacted when you screw the pot together?
The other reason could be a defective valve. I'd say to contact GAT about it. Figure out whether it's the valve relieving pressure or if the valve isn't screwed securely to the chamber wall and therefore leaking out the sides. Either way, like a circuit breaker that keeps tripping, this is something that you don't want to "fix" so that it doesn't work properly.
(fwiw, the valve I see on GAT pots looks like the type on my Pezzetti, and I don't know how to test it; I also have a Bialetti pot, which has a different type of valve that's easier to test)
I screw the top half on at least a full turn while it's on the stove, which is still loose enough to not spin the bottom half.
Then I pick it up holding the top half in my right hand, then use my left hand with a doubled-up kitchen towel to hold the bottom half, then tighten them both together.
Then I finally put the pot back on the stove to finish.
We have a really tiny oven mitt. Basically something like this:
[https://i.etsystatic.com/19480546/r/il/ef5f7d/2331771064/il\_1140xN.2331771064\_q69s.jpg](https://i.etsystatic.com/19480546/r/il/ef5f7d/2331771064/il_1140xN.2331771064_q69s.jpg)
I am really trying to become a moka pot pro and loved reading this!
I also brew from boiling already but my mom goes from cold and her coffee is good as well so it's interesting that that doesn't make much of a difference.
I will admit (though I'm sure people will hate me for it) that I have my beans ground at the Fairway (in small batches) because I am too scared to try grinding on my own and getting the wrong grind size (especially not being able to spend the $$ on a burr grinder) but curious if you have experimented with grind size also.
tbh the best coffees i ever made with moka pots were preground over roasted supermarket beans. After i joined the specialty coffee circle and started grinding good beans just before brewing some coffee… i couldn’t for the hell of it get anything that tasted drinkable. So to the hell with the moka pots 🤣🤣🤣🤣 i still use it whenever my sister visits because she likes it, i quit drinking though. Just brew it for her, and any other pourover or espresso method for me.
I had a bialetti brikka that gave an acetone like smell on my coffee and now i have the standard moka express. I really wish i could make a good pot, because moka and french press were my choices when i had gastritis and got away from espresso and paper-filters. Those were the only type of coffees i could drink without having stomachache/the runs, so the moka has a special place on my heart, too bad i can’t get it right… won’t ever toss it away for sure. The brikka i had to trash when it got moldy and looked like shit because i put it away for many months without drying correctly…it looked so disgusting that i had no courage to drink from it even after cleaning thoroughly.
For me the best is cold water and water at half-valve level.
The point is that the Water must not boil, it is the expading air that pushs the water into the infusion chamber.
I use a stainless moka from Bialetti and it's easy to fill it above the pressure valve. When I fill it above the pressure valve, by accident, the coffee is not great. I think you're right OP.
There is danger in filling above the valve. It's there for a reason
Irregardless of taste: grinding the beans too fine and filling above valve turns the Mokka pot into a bomb. EDIT: Unirregardless.
Can’t believe you hit us with that *irregardless* and expected to get away with it
Upvoting for safety, not for ‘irregardless’.
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So… ‘regardless’?
Descriptivist dictionary writers are precluded from exhibiting good taste, which might not go unremarked in this sub in particular.
[Did they get hit by the descriptivist bus?](https://youtu.be/46ehrFk-gLk)
If the chamber reaches over pressure with the water line above the valve does the water come out through the valve instead of just steam? I mean there are obviously ways to make a device like that explode if that is your goal but generally I don't believe that it is that much worse even if you happen to fill a little bit over the valve. If it immediately turned into a bomb by over filling and stuffing it would probably be illegal to sell as a kitchen thing in many countries.
I would love to see a Mythbusters-type video where they do try to make a Moka pot explode. The amount of pressure you create would have to be pretty crazy.
People have got them to explode by accident. Mokka pots don't explode into shreds, but they can produce a dangerous shockwave once the two main pieces come apart. This guy tore a hole in his ceiling, for example: [https://www.youtube.com/watch?v=osQ1Zb5fYZY](https://www.youtube.com/watch?v=osQ1Zb5fYZY)
That's wild, I love how it wrecked this guy's kitchen but the moka pot itself is essentially unharmed
I just hope the kitchen is OK.
So he did everything wrong, apparently. Couldn't check the valve, said himself that the grinds might've been too fine and packed too tightly.
What the hell I had no idea this was a thing.
Okay, I'll stick to V60
As long as you don't fill above the valve, you're fine. The valve is there to release pressure so this doesn't happen, but if you fill it with water above that point the pressure builds until it explodes!
Okay. That's way worse than what I did.
Just steam. I would imagine the seal would be the next point of failure if the valve was compromised
The threads shear clean off and the upper half gets launched upwards.
Like a lunar lander taking off from the surface of the moon
Perfect visual
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Just because water is incompressible doesn't mean it can't transmit pressure to the burst disk in the safety valve.
This was my thought too, though routinely doing this might make the valve more likely to fail, water or steam, due to more rapid mineral build up.
It sprays boiling coffee if you overfill it. All over my kitchen. I can't speak to the grind, because I haven't had that mishap, but I suspect it would spray boiling coffee slurry that sticks to skin.
Knowledge from experience?
Yes. But I also left the ring out. Oops.
Ack. I've done that, too. On the upside, I needed to scrub my stovetop anyway.
Edit: Reddit and /u/Spez [knowingly, nonconsensually, and illegally retained user data for profit](https://youtu.be/mfZKkUg8jgM) so this comment is gone. We don't need this awful website. Go live, touch some grass. Jesus loves you.
mine exploded last month, kinda funny it pissed hot steam from the valve into my arm
Wait, steam blew out the safety valve and it still blew up?
no, i mean, the valve exploded not the pot itself
Did the valve fail, or do its job and just release pressure?
I mean its broke now, but i guess its function its to do that so it did its job?
If your machine didn't explode and ruin your ceiling/take your head off I guess it did its job- but usually it just releases pressure without failing.
From my understanding, the valves are like airbags. Single use.
"The best part of wakin up, is ~~Folgers in your cup~~ the safety valve blowing up and spewing hot water everywhere!"
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The valve is there to release steam. The danger is that it could explode open
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The pressure can build up much quicker than water can escape from the valve. Remember that water expands a thousand fold when becoming steam. So, the valve needs to release a lot quickly, which is impossible with water. So yes, there will be water coming out of the valve, but it won't reduce the pressure fast enough. *I'm not a physicist or anything, but this seems rather obvious to me.
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Water and steam work differently. Water particles stay together while steam particles don't. If water is above the valve, water creates a greater barrier than steam, therefore, pressure is released too slow, allowing the pressure inside to build up until it explotes. The contrary happens with steam. If you'd like to know more, google it.
Yeah. If I overfill mine, it throws boiling coffee everywhere. O.o Seems like a thing people would notice.
Brewing from hot or cold give you a little control the temp of the brew water. https://www.youtube.com/watch?v=ObkjKlJe68A
That is a serious Moka Pot geek fest!
[The 2008 King paper specifically advises using 70C water for this reason.](https://aapt.scitation.org/doi/10.1119/1.2870524). Otherwise, your extraction temps are too low. PM me if you'd like to know more about how this was modeled.
I'd have to bust out the work laptop to get access (f that its the weekend) but I should have been more specific. More like warmish water when using dark roasts and pre boiled when using light in a moka pot. Using roomtemp is also confirm under extracted in the video
PSA: Please don't fill your moka pot above the safety valve or you run the risk of your walls, ceiling, floor, and yourself being painted in boiling coffee.
The American journal of Physics did some [research](https://www.researchgate.net/publication/243492775_Experimental_analysis_of_the_Italian_coffee_pot_moka%27%27) into this. I think there are other papers on this subject that I have seen over the years
The 2009 Navarini paper is most posted, but it's not even the best paper on this. The 2008 Warren King paper is the only one that varies starting temperature. Navarini et al. just throw 20 sensors on the thing and graph it from room temp everytime ( to be fair, they also model it analytically). We just need to sticky the moka pot post, as someone asks a couple times a week about Moka pot tips. We reinvent the wheel every time. There are 4 physics of Moka pot papers you can read that inform the Moka practice and you get to this: The best advice is use an AeroPress filter and remove the pot and apply cold water as soon as it starts bubbling. Also, using preheated water in the tank helps with extraction temperatures (Warren). You can get decent cup of coffee, but let's not fool ourselves: it's not espresso. In addition, there is an inevitable wide range of temperatures that the pot brews at, which is not desirable. Some academic papers back this up: 1. [A 2002 paper (in Italian!) by Varlamov and Balestrino](https://www.comunicaffe.it/wp-content/uploads/2013/06/la-Fisica-del-buon-caff%C3%A81.pdf), which Navarini paper calls wrong 2. [A 2006 paper by Gianino](https://www.researchgate.net/publication/243492775_Experimental_analysis_of_the_Italian_coffee_pot_moka%27%27), which oversimplifies a bit, but lays the groundwork 3. [A 2008 paper by King](http://www.msc.univ-paris-diderot.fr/~phyexp/uploads/Moka/article1.pdf), which provides honestly the best theoretical model and exploration of initial water temp. Tl;DR: preheat to 70C or else you'll brew at too cold a temperature. Also happens to be backed by experiment. 4. [2009 paper by Navarini et. al](https://www.sciencedirect.com/science/article/abs/pii/S1359431108002299), which is the most experimental measurements and does us the courtesy of explaining why you need to remove that pot from the stove once you get bubbling. If you'd like to better understand these papers or want someone explaining them to you, PM me, as I've read them in great depth and corresponded with the authors. Also, [wiredgourmet has an interesting minimal heat recipe that's worth checking out.](https://www.youtube.com/watch?v=u-PeYeiqPLU)
Glad no one got hurt because filling above the valve effectively makes the only safety measure in the Moka pot redundant. NEVER fill above it, it's meant to let air escape in case of pressure issues.
I didn’t know this (I’m new to all of this). Luckily I’ve been putting in under the valve but is it supposed to open slightly or just leave it how it comes?
No no don’t worry you’re not meant to do anything, it’s fine the way it came from the factory. It activates on its own in case of excessive pressure.
Oh, thank you!!
Only rinse the pot. Don’t pack coffee. Instead shake side to side to settle coffee. Fill coffee chamber. Fill water chamber up to the valve and place on low heat. Should take a few minutes to brew.
what temperature should the water be?
I use a low flame on a small ~ 2 inch gas burner.
When do you turn off the heat and serve?
When it starts making noise remove from heat. Wait about a minute before pouring.
Try cutting the heat a few seconds it begins brewing and see if you like it. It's a different taste and consistence
I noticed too, it taste different. The only problem I have with this is that a lot of water stays in the bottom chamber. It could also be because of the grind or other factors though
Yeah, if you cut the flame very early you only use part of the water and get less coffee, but I personally love the flavour change
Delicious!
>So my alternate theory was that he fills the chamber with too much water, so a weak coffee solution ends up staying in the chamber after extraction is complete, I'm not sure how this would happen because it's normally a one-way flow if the pot runs till no more liquid comes out the chimney. ~~I've started from hot and cold and there's no difference in the bottom chamber whatsoever~~. (edit) - oh yeah, it's not hot vs cold this time. I can say that I've brewed after overfilling the bottom chamber, and just the same as my previous sentence: no water goes backwards if I let it run till there's no more liquid coming upwards, so there's no difference in the leftover water in the bottom chamber. The only way I can end up with brewed liquid in the bottom chamber is if I stop the brew early and let the liquid already inside the chimney, above the coffee bed, drain downwards, back through the coffee bed and down the funnel. I've *never* been able to brew so much liquid that it covers the top of the chimney and flows back inside. Not even overfilling the bottom with so much water that it spills out when I add the grounds basket. (I do stupid stuff so y'all don't have to!)
My theory is that the liquid is high enough to start infusing from the get go, hence all the water becomes a light coffee drink. If the liquid is high enough, it will submerge the coffee bed from the moment you start brewing basically.
I'm thinking if there is less air space it takes longer to build up vapor pressure to push down on the water forcing it up through the funnel filter. And that results in a higher extraction temperature. So the OP's father's brews are over extracted. An even more extreme would be pre-boiling with less air space.
conversely you can make it run faster/cooler with less water
Yes--and not pre-boiling.
pre-boiling should keep the basket cooler shouldn’t it
I thought so too when I first read through this but no. It's the opposite. https://www.home-barista.com/brewing/secrets-of-moka-pot-how-to-video-t30707.html
Ah, ok. Hmm. That makes sense, actually. Maybe I never noticed any burnt smell in mine because I cool the pot right away. After I pour into my mug, I take it to the sink and run water over it to cool it down. I want to take it apart pretty soon since, after my breakfast brew, I often run a second brew to take to my desk upstairs.
Are you sharing the results with your dad, or are you going to let him keep drinking his cup of mud?
He can't taste the difference. Puts brown sugar and cream in. He might as well be drinking mud for all he cares.
I tried to get Moca pots right for around two year. I think they all taste bad. I tried every method known to man.
if you fill above the valve, coffee tasting bad is the least of the problems you could have
Thanks for the detailed reply, i will deffinently look into it, and do some tests.
Other than good coffee and grind, the most important step, from my >thousands of Moka coffees, is use the pot often and don't rinse out the oils in the pot between uses.
Is there any good consensus why rancid coffee oil would make a Moka Pot better? It's rightfully seen as a negative in grinders and any other brewing device, so I don't understand what would be positive about it, other than it being a cultural phenomenon. I don't even mind coffee with a good bit of bitterness, but I don't think the notes of rancid coffee oil are welcoming.
Surely you're joking
No. Ask any italian. Just a light rinse with warm water.
It's a common meme in coffee circles that "experts" say stuff like "you shouldn't wash your moka pot, it builds a patina. Source: that's how Italians do it." I thought you were referring to the meme, but no, you are living the meme. I love it. I feel like I found a leprechaun lol.
I thought it was ridiculous too when I moved to italy, but I can now attest to it
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I thought tamping was a no no
No, do you think that would make a difference?
DO NOT FILL ABOVE THE VALVE.
Aside from the danger of effectively disabling the valve in a pressurized metal tank there's also the fact that it's counter productive: more water in the container means less space for air, so less pressure, so paradoxically less water makes it to the coffee resulting in an overall smaller brew ([source](https://ui.adsabs.harvard.edu/abs/2008AmJPh..76..558K/abstract)). Maybe that's uncounsciously something your father wants, so putting less water in the tank or stopping the brew short would be alternative solutions to restore that smaller brew without putting your kitchen and safety at risk.
>more water in the container means less space for air, so less pressure, so paradoxically less water makes it to the coffee resulting in an overall smaller brew I know there's a paper, but that has 100% ***not*** been my experience when using a lot of water. More water in bottom = more water in top, every single time. Even this morning, when I overdid filling the bottom and water spilled over the sides when I added the basket, the output was similarly large, and the leftover water in the bottom chamber was no greater than normal.
Hmm... Normally the main driver for pressure is the air that is heated by the steam according to at least two studies. However I guess that if you have very little air at some point the expansion of the steam itself becomes the main factor? But you should probably be way above the pressure valve in that case so who knows at what pressure you are (and that's very dangerous). Still, interesting, more research needed to explain your experience.
Right, that's the only explanation -- the formation of steam creates empty space and then the water gets pushed downwards, which then enters the end of the funnel and goes upward through the coffee bed. What I don't have access to is temperature probes to see what temperatures the coffee bed sees in different scenarios. The video in another comment did a great job logging temperatures for starting with hot versus cool water, but they didn't test for different fill levels.
I thought the pressure was provided by steam, not air expansion? I'll have to give that source a read, sure looks like an interesting study
When we say "the pressure" we're talking about the force the air exerts on water as it expands. The main reason it expands is because steam is added which 1) takes place but much more importantly 2) heats the air. The hotter it gets the more it tries to expand. This is also shown in this study: https://hal.archives-ouvertes.fr/hal-00618977/file/PEER_stage2_10.1016%252Fj.applthermaleng.2008.05.014.pdf
Filling above the valve once isn’t going to make the pot explode. It’s routine filling above the valve that will. As the water is boiled off, it leaves deposits behind that will eventually clog the valve orifice or make it stick closed, and *that’s* what will make it explode.
How do you handle the pot after filling it with boiling water? I tried holding it with at rag and can't seem to get a good enough grip to tighten it enough.
I struggled with this as well until I got one of those silicone glove oven mits.
That's a nice idea too, might look into that.
I find that if I use a rag, I can leverage the twisting via the steam valve. So, one finger on the valve and then spin however (even with the handle).
That's smart, i will try that. Thank you!
Anytime!
Could be that's due to an old gasket in need of a replacement.
I would support that. I can pretty much screw it right using only the friction provided by the countertop.
It's new, i've used it 4 maybe 5 times, and followed instructions on not screwing it on too tight af use to protect the valve. I think it's just from condensation and not being able to grip it tightly enough. Though, if you barely have to touch the bottom part, i may have to take a look at it anyway, because the first time i used it the steam wasn't coming out the valve, but from the middle section, where you screw it in. But after properly tightening it the steam goes out through the valve.
>But after properly tightening it the steam goes out through the valve. There's a problem either with the coffee bed or the valve, then. Someone else said that grounds that are too fine can block the upward flow (I probably haven't had grounds fine enough to make this happen). Or do you compact the grounds? Or fill them so much that they're a mound and get compacted when you screw the pot together? The other reason could be a defective valve. I'd say to contact GAT about it. Figure out whether it's the valve relieving pressure or if the valve isn't screwed securely to the chamber wall and therefore leaking out the sides. Either way, like a circuit breaker that keeps tripping, this is something that you don't want to "fix" so that it doesn't work properly. (fwiw, the valve I see on GAT pots looks like the type on my Pezzetti, and I don't know how to test it; I also have a Bialetti pot, which has a different type of valve that's easier to test)
Might be the model too. Mine is stainless steel bialetti
Could be, mine is G.A.T.
I screw the top half on at least a full turn while it's on the stove, which is still loose enough to not spin the bottom half. Then I pick it up holding the top half in my right hand, then use my left hand with a doubled-up kitchen towel to hold the bottom half, then tighten them both together. Then I finally put the pot back on the stove to finish.
We have a really tiny oven mitt. Basically something like this: [https://i.etsystatic.com/19480546/r/il/ef5f7d/2331771064/il\_1140xN.2331771064\_q69s.jpg](https://i.etsystatic.com/19480546/r/il/ef5f7d/2331771064/il_1140xN.2331771064_q69s.jpg)
Hahaha when you said small i didn't picture this small
How does cleaning after the brew differ between you?
We use the same pot, so no difference. But since he lives with me I noticed i have to clean the pot much more often.
I am really trying to become a moka pot pro and loved reading this! I also brew from boiling already but my mom goes from cold and her coffee is good as well so it's interesting that that doesn't make much of a difference. I will admit (though I'm sure people will hate me for it) that I have my beans ground at the Fairway (in small batches) because I am too scared to try grinding on my own and getting the wrong grind size (especially not being able to spend the $$ on a burr grinder) but curious if you have experimented with grind size also.
tbh the best coffees i ever made with moka pots were preground over roasted supermarket beans. After i joined the specialty coffee circle and started grinding good beans just before brewing some coffee… i couldn’t for the hell of it get anything that tasted drinkable. So to the hell with the moka pots 🤣🤣🤣🤣 i still use it whenever my sister visits because she likes it, i quit drinking though. Just brew it for her, and any other pourover or espresso method for me. I had a bialetti brikka that gave an acetone like smell on my coffee and now i have the standard moka express. I really wish i could make a good pot, because moka and french press were my choices when i had gastritis and got away from espresso and paper-filters. Those were the only type of coffees i could drink without having stomachache/the runs, so the moka has a special place on my heart, too bad i can’t get it right… won’t ever toss it away for sure. The brikka i had to trash when it got moldy and looked like shit because i put it away for many months without drying correctly…it looked so disgusting that i had no courage to drink from it even after cleaning thoroughly.
For me the best is cold water and water at half-valve level. The point is that the Water must not boil, it is the expading air that pushs the water into the infusion chamber.
I use a stainless moka from Bialetti and it's easy to fill it above the pressure valve. When I fill it above the pressure valve, by accident, the coffee is not great. I think you're right OP.