When purchasing a semi-automatic or manual espresso machine another very important thing to consider acquiring is a tamper. A tamper is the critical tool for leveling and compacting ground coffee in a portafilter to make espresso. Some espresso machine manufacturers include a tamper with the machine, but many do not. Espresso coffee tampers come in a variety of materials among them stainless steel, aluminum, chrome plated steel, and plastic.
Solid plastic tampers will eventually curl up around their edges and not seal properly when tamping giving you an undesirable poor quality shot of espresso. They should be replaced with either an aluminum or stainless steel tamper. This raises the question: Which is better, an aluminum or stainless steel tamper?
To answer this question you need to know the purpose of a tamper in the espresso brewing process. A tamper simply levels and compacts espresso ground coffee in the portafilter. This is important because if the ground coffee is not level and packed tightly (in addition to being consistently and finely ground), during the brewing process the hot pressurized water will move either too quickly through the espresso grinds, not saturate the ground evenly, or both which gives you a poor quality shot of espresso with little or no crema.
A tamper sized correctly for your portafilter is important because it needs to seal properly around the edges of your portafilter to ensure tightly packed espresso. So, if your tamper is of the correct diameter for your portafilter, either an aluminum or stainless steel tamper will work very well. One significant difference between them is stainless steel tampers are often heavier and may help you easily achieve the 30 pounds of tamp pressure which most experts consider to be the perfect pressure.
Other tamper features to consider are the shape of the surface (flat or convex), the style to fit your decor, and special features like pressure sensing feedback.
As to whether a flat or convex tamper will give you better results really depends on personal preference and experience. Some people say the convex tamper is better because it matches the convex shape of some brew baskets, giving you a more consistent tamp. While some people say they use both tampers depending on the grind they are using, and have seen a difference, I myself am old school and like a flat tamper because it gives me a nice flat consistent tamp and always good results.
A tamper often sets in plain view on the counter near the Espresso machine and you may want it to match your carefully considered décor. Reg Barber Logo Tampers come with wood handles, Espresso Gear Presso Luce Tampers are very colorful, and The Ultimate Tamper is a highly polished work of art.
Some tampers like the Espro Calibrated Flat Tamper have built in mechanisms that sense when you have applied the proper 30 pounds of pressure and will “click” letting you know you have reached tamping pressure perfection!