It’s not that cone filters won’t make a great cup of coffee — the OXO On 9-Cup still ranked fifth out of 10 in our taste test. But flat bottoms generally allow for the grounds to be more evenly extracted and increase the coffee’s flavor. (It’s no coincidence our other three recommendations have flat-bottom brew baskets). You may have to do a little more tweaking to get this coffee maker’s brew to the best it can be, and that’s the other reason we like the 12-cupper more. This smaller version doesn’t let you tinker with water temperature.
With the introduction of the electric drip coffee maker for the home in the early 1970s, the popularity of percolators plummeted, and so did the market for the self-contained ground coffee filters. In 1976, General Foods discontinued the manufacture of Max Pax, and by the end of the decade, even generic ground coffee filter rings were no longer available on U.S. supermarket shelves.
The principle of a vacuum brewer was to heat water in a lower vessel until expansion forced the contents through a narrow tube into an upper vessel containing ground coffee. When the lower vessel was empty and sufficient brewing time had elapsed, the heat was removed and the resulting vacuum would draw the brewed coffee back through a strainer into the lower chamber, from which it could be decanted. The Bauhaus interpretation of this device can be seen in Gerhard Marcks' Sintrax coffee maker of 1925.
The simplicity starts with its design: a single button with a scrolling dial underneath an LED interface. That button is the only one on the entire machine. With it, you set the time, set the water temperature, set how many cups you want brewed, and when you want the brewing to start. It takes a second to get the hang of it, but we were impressed with how intuitive it is — a stark contrast to a machine like the Moccamaster KBT 10-Cup Coffee Brewer, which had so many extra pieces, it required constant consultation of the instruction manual.
The Mr. Coffee Optimal Brew coffee maker System has a highly modular design, with its rectangular water reservoir easily sliding in and out of the chassis. For those who only want a cup of basic coffee, you will find that the Mr. Coffee Optimal Brew coffee maker System will do that very well – its "brew now" button is found on the front of the machine.
It can take a little while to get to know the ins and outs of a new coffee maker. In CR’s labs, each drip coffee maker we test brews roughly 65 cups by the time our engineers are through with it. And brewing is just one of many aspects we look at. We test for handling and convenience, too, so you can choose a model that helps you sail through morning madness. 
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