Espresso Basics by James Grierson

This is the basic technique to brewing espresso. Once you have mastered this you can then start to experiment and find your very own 'Espresso Nirvarna'
Use filtered water in your espresso machine. Water from the tap may contain particulates (such as dirt, sediment and rust) that can affect the taste, texture and aroma of espresso. Particulated water also causes added wear on parts; and can clog solenoids, valves and groupheads.
You should aim to complete all these steps as quickly as possible, but it is important not to rush any stage, particularly the tamp.
1. Fill the water tank of your espresso machine with filter water, attach the portafilter (empty at this stage) and turn on the machine. Wait for the machine to warm up.
2. Switch on the espresso function (pump) and allow hot water to pour out the portafilter for between 10-20 seconds. This will ensure that the grouphead and portafilter are hot. A small variation in temperature can make the difference between a great espresso and a passable one, so it is very important to ensure that the water inside your espresso machine is at a constant temperature.
3. Remove the portafilter and quickly wipe dry with a soft clean cloth.
4. Grind you coffee beans and dispense 7 grams of grounds (14 grams for a double shot) into the portafilter basket. Level the grounds by gentle knocking the portafilter against the palm of your hand a couple of times.
5.Use a coffee tamper to press down the coffee grounds into the portafilter basket to form a tight puck. You should apply 30lbs/13.6kgs of downwards force to avoid the 'channelling'. Before you remove your tamper, twist it round to leave the puck with a polished surface. The concept behind tamping: is to ensure that the grounds are evenly distributed in the basket; and that there are no tiny air pockets. The tamp is very important as water always seeks the path of least resistance; so if you tamp light or not at all, the water will find the areas where there is least grounds and channel through them. The resulting espresso will be thinner and taste under-extracted. To work out exactly how much pressure to exert, practice pushing down your tamper on the bathroom scales till you reach the 30lb mark.
6. Attach the portafilter back onto the machine and switch on the pump. Ideally, it should take between 25-30 seconds to produce a 1.25oz/35ml shot (or 2.5oz/70ml for a double shot). If it takes longer than 30 seconds, adjust your grinder to a slightly coarser setting; and if it takes less than 25 seconds, adjust your grinder to a slight finer setting. It will take several attempts with a new grinder to get it dialled exactly right for your espresso machine.
N.B. The level of moisture in the coffee grounds affects the flow-rate of espresso, as the higher the moisture content the tighter the grounds will pack. As different espresso blends contain different levels of moisture you will need to adjust the settings on your grinder accordingly. Also as coffee is hydroscopic (it absorbs moisture from the atmosphere) it is therefore, a good idea to regularly monitor the flow-rate of espresso, even if using the same blend, as changes in humidity may need to be compensated by altering the grind slightly.
About the Author
James Grierson is the owner of Galla Coffee: http://www.gallacoffee.co.uk/ - UK online retailer of designer coffee accessories. Through the Coffee Knowledge section of his website he aims to help people understand more about coffee and give them tips on how to make great tasting coffee in their home.
Check out http://www.gallacoffee.co.uk/acatalog/Coffee_Knowledge.html for more articles.