How to get the correct expresso extraction amount, grind vs tamper

Question

I'm trying to extract a double shot, e.g 60ml in 30 seconds. I always seem to go over and get 100ml+. When I use a finer grind, the coffee tastes burnt... It seems that tampering harder and using a finer grind have the same effect.

How do I know which method to use? e.g. why not use a really fine grain and not tamper at all? why not use a croase grind and tamper really really hard?

Answer 1

There are two things happening when you make espresso:

1. The pressure of the espresso machine pushes the water through the grounds faster than most other coffee-making methods. In general, the good flavours in coffee are highly water-soluble and the bitter, acidic parts are less water-soluble, so by pushing the water through the grounds quickly, you get proportionally more of the good stuff and less of the bitter.

2. More significantly, by grinding the coffee very finely and packing it in (tamping), the water doesn't just flow past the coffee particles, the pressure forces the water through the particle where it pushes out some of the aromatic oils which form an emulsion in the liquid.

That emulsion - the crema - is what makes espresso different from coffee, and you need both a fine grind and tamping to get it.

If you're really keen on getting this right, you could start by checking your temperature and pressure - you want ~200 F and ~9 bars.

Your extraction time (30s) is good, and so is going for a double shot, but I'm not sure what you mean by "always go over." If you're getting good crema, it should ooze out, almost like honey or syrup, and you should stop the extraction when it starts to turn whitish. If that happens in less than 30s, you should grind your coffee a bit finer and try again. If it takes more than 30s, you need to go a bit coarser.

If you still find the espresso tastes burnt, try different beans.

Answer 2

Making a good espresso is non-trivial. To achieve that, a lot of things must be "just right". Based on your description, I am guessing that your flow is WAY too fast. The usual culprit is that you need to grind the coffee beans finer.

As mentioned above, start with the temperature and pressure of your espresso machine. Exactly what machine are you using? Does it allow you to control the temperature? I had very random results making espresso until I bought a PID kit to control the temperature.

Of equal importance is your grinder - you need a very fine grind. Most grinders simply don't grind fine enough for espresso. A really good grinder can easily cost the same $$$ as the espresso machine.

I was mystified by the hard tamp / light tamp concept when I started out. What I learned from experience is that a light tamp is generally fine.

How much coffee are you using? I weigh mine for each shot (before grinding). I typically use 15g of coffee beans for a double shot. I adjust the grind to pull the shot in 25 seconds.