While there are a few key factors that go into the best cold brew makers, a good filter is one of the most important ones. The best filters are typically made of high-quality stainless steel with mesh that's ultra-fine so sediment doesn't accumulate at the bottom of the carafe and leave you with a gritty or sludgy texture.
Another factor to think about is the coffee maker's carafe or pitcher. Borosilicate glass is usually the best material as it isn't as vulnerable to extreme temperature changes and it also handles impacts better (which means it's harder to break if you drop it). Additionally, borosilicate glass doesn't absorb flavor like plastic does so your coffee will taste fresher and more pure.
Lastly, think about practical things like how easy the coffee maker is to clean, or how well it fits (or doesn't fit) in your fridge and cupboards. Tall pitchers, for example, can be difficult to fit on your refrigerator shelves, and bigger units can be more cumbersome to store when not in use.
How does a cold brew coffee maker work?
Each coffee maker will have a slightly different system of operation, but there are several guiding principles to cold brewing that will help you get the most out of your new device:
Aim for a 1-cup-to-1-ounce ratio: The best cold brew is usually the result of a ratio that's roughly a cup of water to an ounce of coffee grinds. Start with this formula and tweak it as necessary depending on your tastebuds.
Dial in your steeping time: You'll need to do some experimenting to find the magic number that fits your personal preferences; however, watching the time carefully will help you dial it in. Optimal steep time ranges from 12 to 20 hours.