So I try to grind about the same each time but for some reason if I don't hit the jackpot on adjusting my hand grinder I get sour or bitter coffee. Why is my Moka Express so finicky?

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    Just a tip: Try to grind exactly the same amounts every time rather than about the same. Minimising variables will help you diagnose your problem better. In this case, it seems like you're betting it all on grind size. Moka pots are very sensitive and you should ensure that you are placing on a constant medium-high heat source. You should see the coffee ooze out the top very slowly to begin with; this is a sign of a good extraction. Ensure your water to coffee ratio is the same every time, ensure good temperature gradient and extraction time and you should be golden.
    – Shiri
    May 15 '17 at 14:41

Actually, this question is self explanatory. I assume you only need some guidance and confirmation for what's going wrong.

A better known fact is:

  • if your coffee is underextracted, it tastes sour.
  • if your coffee is overextracted, it tastes bitter.

Now, let's tie up this to grind size:

  • if your grounds are finer, your coffee overextracts if other conditions are kept stable.
  • if your grounds are coarser, your coffee underextracts if other conditions are kept stable.

It's known that Moka pots are not controllable devices. So, all the other conditions (temperature, pressure, etc.) are nearly same each time. Thus, it's obvious that your grinding directly affects the taste of your cup. You should be consistent about your grounds. :)

And a final note, one of the jewels of this site is this extraction chart that you may check.

  • I was just messing with a Moka Pot last night for a customer. Think pulling espresso shots without ANY of the pressure or temperature controls.. we got serviceable coffee, but I definitely agree, not the optimal way to brew coffee. If you are jonesing for espresso and don't have the funds for an espresso machine this may be an option, but otherwise it wouldn't be my preference.
    – Nate M.
    May 18 '17 at 15:38

Reading the following makes me sad:

Moka pots are not controllable devices

A Moka pot (or Percolator) in fact is a controllable device. I use them since more then a decade with success with a much lower level of control as I list you here:

  1. Measuring temperatur
  2. Scientific paper about applied thermal engineering and moka pots
  3. Using laboratory equipment for brewing coffee with a moka pot

The easiest is to start with:

  1. Use a grinder
  2. Preheat the plate (I use 7-8/12 on electric stove)
  3. Use very warm (not hot and surely not cold) water
  4. Put the pot off of the plate before the coffee is finished as in the end you get water instead of coffee due to the coarser grains bleeding out earlier
  5. Do not temp the coffee, especially not hard, but get one of the cheap plastic tampers and tamp if slightly, but even
  • Ah! I meant "directly controllable during brew time". Sorry. Excuse my engineering background.
    – MTSan
    Jun 11 '17 at 21:28
  • Same background here, so let me ask these questions: (1) Why not controllable if the procedure can be repeated? (2) Why not during brewing time? (3) Where is the uncontrollable part during brewing time?
    – kaiser
    Jun 11 '17 at 22:15
  • I feel like this turns out to be a nice discussion. I assume we just have different perspectives: Let me explain. When I say control, I would like to control the procedure directly by myself, by touching it. Not indirectly by the result of some differential equation. Even then, the brewing happens when the vapor passes through the grounds. You have the grounds tightly screwed in into the container. You cannot mix, stir or tamp them at that moment. The temperature of the vapor is always close to 100 degrees Celsius. The pressure is water's gas pressure and constant. So, nothing to change.
    – MTSan
    Jun 12 '17 at 15:37
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    Of course, you can still change many things as you have mentioned. The grind size, amount of coffee, amount of water, tamping, pre-heating the water or the stove (or simply changing the heating up time of the water). But I consider all these things as pre-brew changes, not brew-time changes. (This resembles me compile time modifications of a source code and runtime modifications of source code.) For example, in V60, you can stir the grounds, wet them prior to infusion to bloom, etc. Such things are not possible in Moka pots. Or, if these are possible, I would like to hear gladly.
    – MTSan
    Jun 12 '17 at 15:41
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    @MTSan I get your points! Completely valid arguments. I would assume that comparing a Percolator to a Melitta/ V60 is too far away. IMO it's more like a cave men version of an E61 espresso machine. On the opposite —and I stopped drinking Melitta-style coffee a decade or more ago, so never any effort on my end here— I am not sure if there is a big chance of having a scientifically correct and repeatable stirring mechanism in a brew over. Controlling during brewing time should be enough by time and "pre-brew" :D efforts to make results comparable.
    – kaiser
    Jun 12 '17 at 19:15

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