Prior to the introduction of pre-measured self-contained ground coffee filter rings, fresh coffee grounds were measured out in scoopfuls and placed into the metal percolator basket. This process enabled small amounts of coffee grounds to leak into the fresh coffee. Additionally, the process left wet grounds in the percolator basket, which were very tedious to clean. The benefit of the Max Pax coffee filter rings was two-fold: First, because the amount of coffee contained in the rings was pre-measured, it negated the need to measure each scoop and then place it in the metal percolator basket. Second, the filter paper was strong enough to hold all the coffee grounds within the sealed paper. After use, the coffee filter ring could be easily removed from the basket and discarded. This saved the consumer from the tedious task of cleaning out the remaining wet coffee grounds from the percolator basket.
If you push the 54mm stainless steel portafilter into the hands-free grinding cradle, the grounds will go right into the filter. The grinder shuts off when it's done, too, so you don't have to worry about figuring out if you've got the right amount. Finally, the included 54mm tamper ensures that your grounds are evenly pressed, so you get the most out of your beans.
Percolators began to be developed from the mid-nineteenth century. In the United States, James H. Mason of Massachusetts patented an early percolator design in 1865. An Illinois farmer named Hanson Goodrich is generally credited with patenting the modern percolator. Goodrich's patent was granted on August 16, 1889, and his patent description varies little from the stovetop percolators sold today. With the percolator design, water is heated in a boiling pot with a removable lid, until the heated water is forced through a metal tube into a brew basket containing coffee. The extracted liquid drains from the brew basket, where it drips back into the pot. This process is continually repeated during the brewing cycle until the liquid passing repeatedly through the grounds is sufficiently steeped. A clear sight chamber in the form of a transparent knob on the lid of the percolator enables the user to judge when the coffee has reached the proper color and strength.

Prior to the introduction of pre-measured self-contained ground coffee filter rings, fresh coffee grounds were measured out in scoopfuls and placed into the metal percolator basket. This process enabled small amounts of coffee grounds to leak into the fresh coffee. Additionally, the process left wet grounds in the percolator basket, which were very tedious to clean. The benefit of the Max Pax coffee filter rings was two-fold: First, because the amount of coffee contained in the rings was pre-measured, it negated the need to measure each scoop and then place it in the metal percolator basket. Second, the filter paper was strong enough to hold all the coffee grounds within the sealed paper. After use, the coffee filter ring could be easily removed from the basket and discarded. This saved the consumer from the tedious task of cleaning out the remaining wet coffee grounds from the percolator basket.
This testing was designed to highlight the difference in how each machine extracted its coffee grounds. Remember, extraction is tied to water temperature, how long the grounds had to steep, and how evenly that water is distributed in the brew basket. (Depending on how the machine distributes the water and the shape of the basket, any particular ground may or may not receive the same amount of time in contact with water — thus any individual grind may be over-extracted, under-extracted, or just right.) Properly extracted grounds would have a balance of notes and aromas, from slight hints of acid to a pleasant amount of bitterness.
Our brew-performance tests measure the brew temperature and contact time (how long water stays within a sweet spot of 195° to 205° F for brewing). We measure concentration using a refractometer, a device that measures the amount of coffee dissolved in each brew. Our convenience tests look at how easy it is to set timers, fill the reservoir, clean the machine, and more. And for the first time, we’re incorporating predicted reliability and owner satisfaction ratings into the new Overall Score for each model. We determine these ratings for each drip coffee maker brand using survey data collected from thousands of CR members.
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