A tamper is a tool used by baristas to press the coffee into the portafilter, or handle, of the coffee machine.
There are very good reasons to use a tamper, and while many baristas might loudly promote their favourite technique, there are some basics that anyone should know.
First of all you need a tamper that fits your espresso machine's baskets. Often the tamper supplied with the machine is undersized. This means you tamp unevenly across the surface of the coffee 'puck' which allows the water under pressure an easy path through any fractures or pressure points - meaning your espresso is really only brown water as it missed most of the coffee on its way through.
Firm, even tamping with a proper sized tamper means that the water has to flow through all of the coffee in the filter, extracting the sugars, aromatics and caffeine that make coffee what it is.
So you need to find a tamper that fits - and this can be a challenge. The big range of domestic espresso machines has resulted in a variation of filter sizes ranging from around 45mm through to 60mm. 53 and 58mm are the most common, but there is often variation in these in that while the filter basket may officially be 58mm the physical size may well be a millimetre or so either side of this.
The most effective way to ensure a perfect fit is to have a Tamper custom made - Pullman Tampers in Adelaide are experts at this and the lovely timber handles ensure that any coffee snob would love one as a present. For many people, the custom tamper is probably an extravagance, at least at first.
I'd recommend that if the tamper supplied does not fit well that you try a few others out for size - this may mean taking the little filter basket out shopping with you. Some kitchen stores stock tampers but you'll more likely find a suitable one for sale in a store that specialises in espresso machines.
The first tamper is a double ended 53/58mm tamper - around $8 but not a great tamper to use.
The second is supplied with the machine, and is OK but still leaves a ridge of coffee around the outside of the prtafilter. This can disrupt to flow of water and 'channel' it around the puck rather than an even flow through the puck.
Finally we have the custom made tamper with a very neat fit, almost no grains of coffee escape this beauty.
The heavy base also makes it much easier to use as the mass of the tamper does much of the work for you.
The basic techniques that you end up adopting need to be consistent. Tamping is one of several variables that can significantly effect the final result in the cup - and while you tweak one variable you need to keep the others as stable as possible.
I'll go into some more detail about this in part two of this Domestic Coffee post, but part two will have continue in a day or so. It will involve me taking photos while grinding and using the machine and right now both the Junior Grendels have just gone nighty-nights, and I really don't want them waking up and asking for coffee!