Function

• The tamper is used to pack the ground coffee into the basket of an espresso machine. The water used in making espresso is under high pressure; tamping helps the water flow through the coffee evenly to ensure proper brewing.
  
  

Benefits

• Without tamping or with improper tamping, the water may go through the coffee unevenly, which means a portion of it will be under-brewed and another portion will be over-brewed. This can affect the crema, the light brown foam that makes espresso distinctive.
  
  

Using a Tamper

• Once you have measured the ground coffee into the basket and placed the basket in the porta-filter (the coffee receptacle with a handle that attaches to the machine), use a tamper to gently press down on the grounds. Give the tamper a twist before lifting it. This process should create an even-looking surface.
  
  

Types

• A tamper has a handle and a circular base designed to fit the porta-filter. Depending on the design, the tamper can have a flat base, a rounded (convex) base or an inverted (concave) base. Although espresso machines designed for home use often come with a plastic tamper, most coffee experts prefer a heavier tamper with a metal base. The handle may be made of wood, plastic or metal.
  
  

Selecting a Tamper

• The most important factor to consider when selecting a tamper is if it fits your machine well. If it is not a good fit, you can end up with loose grounds. If you will be brewing espresso often, the weight of the tamper and the feel of the handle may also be important to consider. There is debate about whether a rounded or flat base results in better espresso, so that design feature comes down to personal preference.