Manual espresso machines have a certain charm. You get a no frills, no nonsense piece of equipment capable of producing delicious espresso shots, together with a well-built machine with a low number of moving parts with low complexity. This leads to them being able to last a lifetime.
The Cafelat Robot is designed with such a goal and I’m in love with it. Today we talk about how to work with it to produce great espresso.
First off, I cannot emphasise how important puck prep is. Puck prep is the process where you prepare your coffee grounds before extraction. For espresso, and coffee brewing in general, you want an even extraction of coffee over the coffee bed. Over extraction (too much flavour extracted at a localised section of the coffee bed) will result in bitter, unpleasant flavours and under extraction (too little flavour extracted from parts of the coffee bed) will lead to sourness. We want balance.
Preparing the coffee grounds properly helps even extraction. When I first used the robot, I ground coffee using the Timemore Chestnut ESP (around 14 clicks), tamped, placed the Cafelat metal filter, then used a hot water dispenser to fill the basket. This resulted in channeling, where water was making it’s way through a section of the coffee faster than the rest, because of the dent the dispenser made on the puck bed. I only realised this after 5-10 shots. I now use a pour-over kettle to fill the basket, taking care not to agitate the puck bed.
I also use a WDT tool (a needle that breaks up clumps of coffee grounds) to try to get a homogenous bed of coffee before tamping.
The above video is an example of a decently homogeneous extraction extraction with the robot, after the puck prep with WDT and using a low flow rate kettle for filling the basket.
This on the other hand, is an example of channelling happening during extraction. You can see a dominant flow of liquid through one side of the basket. This was probably due to the water dispenser agitating one part of the coffee bed upon contact, leading to that localised bit of coffee bed to be cratered. Water thus flows faster through that portion, leading to over extraction of that localised area.