Filter coffees versus Espresso. Rules and Realities.
Now this is a blog post to read carefully!
The main difference between filter coffee and espresso is time and that is related to water weight.
When brewing espresso the longer the shot (time) the weaker the coffee. This is because the amount of actually coffee grinds (dose) is fixed and does not change. However the amount of water that goes along and travels through is ever increasing.
For example a 20 gram dose tamped into a Portafilter and inserted into an espresso machine at a certain grind size (for arguments sake say 400 median microns) will take. 30 seconds to our a 30 gram espresso (yeild). That yield is probably around 10% coffee grinds (Total dissolved Solids or TDS) and 90% water.
You have therefore an extraction yield of 15% (you have carried 15% of the beans potential into the cup). That’s a VERY STRONG ristretto.
If you change the TIME (this is where filter coffee is the opposite later in the post) to 1 minute (60 seconds). You will find that the dose doesn’t change but the yield (final espresso volume) increases exponentially.
In this same example the 20 gram dose with a 60 second shot time yields 120g of VERY WEAK espresso. Here’s the extraction yield:
Yield divided by Dose Times TDS
80/20*6.6 = 26% extraction yield. This coffee would be much weaker and not necessarily tasty.
Filter coffee is a totally upside down graph. (We’ll show this all graphically at the end).
The brew weight (yield or water) is FIXED as well as the dose. The time is the main factor you will be playing with.
If you pour an aeropress there is only so much water you can fit. The brew time and strength then depends on how long (TIME) you spend before filtering the coffee. This time cannot be extended in a pourover or chemex other than by grind size and agitation because the water will flow through the paper and into the cup freely. In terms of inverted aeropress or French press you can steep the coffee indefinitely HOWEVER the water weight (yield) will always be fixed.
This creates an inverse relationship between filter (drip) coffee and espresso. The longer you brew espresso the weaker it gets, whereas the longer you brew filter coffee the stronger it gets!
Doesn’t this tantalise your mind? Are you being mentally undressed? Do you feel the need to study more? I hope so.
Here’s me judging Siphon at 2016 Australian International Coffee Awards