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.
A number of products are sold for the convenience of consumers who do not want to prepare their own coffee. Instant coffee is dried into soluble powder or freeze dried into granules that can be quickly dissolved in hot water.[61] Canned coffee has been popular in Asian countries for many years, particularly in Japan and South Korea. Vending machines typically sell varieties of flavored canned coffee, much like brewed or percolated coffee, available both hot and cold.
