Discount K-Cups

Robusta coffee also contains about 40–50 percent more caffeine than arabica. For this reason, it is used as an inexpensive substitute for arabica in many commercial coffee blends. Good quality robustas are used in some espresso blends to provide a better foam head and to lower the ingredient cost. Other cultivated species include Coffea liberica and Coffea esliaca, believed to be indigenous to Liberia and southern Sudan, respectively.

Machines such as percolators or automatic coffeemakers brew coffee by gravity. In an automatic coffeemaker, hot water drips onto coffee grounds held in a coffee filter made of paper or perforated metal, allowing the water to seep through the ground coffee while absorbing its oils and essences. Gravity causes the liquid to pass into a carafe or pot while the used coffee grounds are retained in the filter.[56] In a percolator, boiling water is forced into a chamber above a filter by pressure created by boiling.