Lessons Learned..

Well despite being groggy and half asleep this morning, my Saturday morning coffee turned out like this:

At least it's floral-ish

And it tastes pretty good too (I'm drinking it while writing this entry). On congratulating myself on a great coffee extraction and excellent microfoam, I realised that I needed to correct some information I posted here on techniques.

My coffee experience is a learning process (I expect it always will be) and I had been labouring under a misconception, particularly around the techniques for a good coffee extraction. In my entry 'The Basics' on April 29th I said this:

The tamp, is basically how hard you cram the coffee grounds into the filter basket of the porta-filter. This link  will take you to a site that describes tamping in detail, but essentially you want to have a solid cake of coffee grounds in the filter basket that the water will be forced through evenly. When inserting the porta-filter into the group head of the espresso machine (the only place you can stick the porta-filter) you want some resistance as you lock it in - but not so much that it's a struggle.

The part about wanting resistance as you lock in the portafilter is just wrong, I'll explain why. As I have now learned, if you're feeling resistance as you're locking in your portafilter, chances are good that you have over-dosed your coffee - a mistake that I was making. Essentially your coffee puck (cake, whatever) is then crammed hard up against the showerscreen of the group head.

Originally, I thought that was a good thing, my reasoning being that the whole point was to extract the coffee oils from the ground whilst under pressure, so if there is no clearance between the coffee and the showerscreen, the water has to work harder to get through, therefore more pressure.

I had missed a very key piece of information; a good extraction occurs when the coffee is extracted evenly throughout the whole coffee puck. By overdosing the coffee, I was not allowing pre-infusion to occur (I'll explain that term shortly) and was forcing the water only through the centre of the puck, meaning that if I ever extracted the outer edges of the puck, the centre core would be way over extracted.

On to Pre-Infusion. The term pre-infusion means that the espresso machine wets the coffee puck down prior to building up water pressure and beginning the extraction. I believe pre-infusion occurs at around 4 BARs of pressure. In automatic and a lot of semi-auto espresso machines, pre-infusion is already programmed into the single-shot, double-shot and any other one-button-push operations, you will recognise this as the delay of a few seconds once you have pushed the button, before the coffee actually starts coming out.

On manual machines, as the name suggests, you have to control pre-infusion yourself.

So a quick recap:

• You should have a few mm clearance between your coffee and your group head showerscreen.
• A good coffee extraction is an even extraction throughout the whole coffee puck
• If you're not getting the required pressure from your extraction, adjust your grind finer so that you can increase your dose while maintaining clearance.

A good indicator of a decent extraction is the condition of the coffee puck afterwards, it should be basically dry, for example:

If your puck is sloppy, it means your grind was too coarse or your tamp did not apply enough force.

Hope that helps =D

Brandon.