Did you know that pressure does things to other things? It does! It turns coal into diamonds. It turns beers with friends into tequila shots. And it turns coffee into espressos! Pressure is great!
We are constantly exerting and experiencing some form of force. We are at the same time being pulled down by gravity, and exerting a resisting force with our skin, skeletons and muscles so as to not flop into a 2 dimensional human outline on the ground. It’s really quite remarkable that with all this resisting we have any energy left to do anything other than lie staring at the ceiling. Remember that next time you skip the gym – you’re still doing a solid resistance training session watching TV.
‘Espresso’ is literally Italian for ‘pressed out’, and this is the basic difference between espresso coffee and brewed coffee. With espresso, water is pressed through the coffee, and in brewed coffee it is either immersed or poured over. Technically brewed coffee is also under the force of gravity, but let’s not be nit picky!
As baristas you have the magic tools in our kits to manipulate this pressure and resistance relationship to create an array of remarkable espressos. You have water pumps, grinders, and tampers, all with variable settings, all ready to yield to your every whim and fancy.
You’re familiar with changing the grind to extract more or less from the coffee beans by changing its surface area, but it also has the ability to provide more or less resistance to the water flowing through it. The force of tamping dictates how compact the puck will be, which also provides more or less resistance to the water flow.
Changing the pump pressure is something you may be less familiar with. It’s fairly well known that 9 bars is the optimum level of pressure that water should be pressed through. Now unknow it. Forget about it. Optimum level for who? Noit you! You’re your own person, no one tells you what to do. You’re not a lemming just following the herd! Have some tequila.
A lower pump pressure is less likely to disrupt the puck, and instead of blasting through, exposing uneven distribution, causing rifts and channels and mayhem, and an unpleasant espresso. Dropping the pump pressure means water will pass more gently through the puck, spending more time with the coffee grounds, speaking sweet nothings, tenderly coaxing and massaging rich and melodious nectar into the cup.
A word of caution before you bound with sheer abandon into this new pressure frontier – if it’s not your machine, maybe get permission first. If it is your machine – read the instruction manual!
And lastly, a word of advice. In your thoughts and experiments and manipulation of pressure and espressos, imagine yourself in a wind tunnel, your hair and purple silk blouse whipping in the breeze, and pop on this song. It’s both inspirational and informative. Thank you John Farnham. For everything you have taught us.