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Coffee Makers

Drip coffee 101: Secrets to brewing the perfect cup

Here's everything we learned testing a slew of drip coffeemakers.

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Brewing great coffee at home isn't as simple as you might think. Megan Wollerton/CNET

We usually think of brewing a pot of drip coffee at home as a simple chore. While performing the basic task of pouring hot water over coffee grounds itself isn't too complicated, consistently achieving great-tasting results is far from easy.

After putting a big group of home coffee machines through their paces, here are the key things I learned along the way. Not only did these techniques help me stack prominent coffee appliances against each other scientifically, I'm confident they will help you brew a better cup of joe at home too. Most of you won't want to go to all this trouble, but you've come to the right place if you're looking for a few tangible methods to up your home coffee game.

Coffee in a nutshell

At its core a cup of coffee is merely a water solution containing tiny particles of dissolved solids and compounds. You pour hot water over ground coffee beans. The resulting liquid then passes through a filter of some sort, either paper or gold mesh or steel strainer (as in the case of a French press).

Depending on how you create this concoction though, this beverage can either taste truly sublime or be downright undrinkable. More confounding is that if you're not careful the results can potentially vary wildly, even when you use the same coffee beans from an identical bag roasted within the same batch and at the same time. This is why consistency is important in each step.

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The perfect cup of coffee is flavorful and complex, but not bitter. Brian Bennett/CNET

The ideal brew

According to the Specialty Coffee Association of America (SCAA) there is an ideal method for making coffee, called the Golden Cup Award, which will scientifically yield favorable and repeatable results. You should use between 3.25 and 4.25 ounces of coffee grounds per 64 ounces of water (90-120 grams of coffee to 1.9 litres of water). The water temperature must be at 200 degrees Fahrenheit (+ or - 2; that's equivalent to 93 Celcius) when it comes in contact with the grounds. Lastly, the total dissolved solids (TDS) measured in any given brew tastes best to most people when it falls between 1.15 and 1.35 percent.

Sounds pretty straightforward doesn't it? I thought so too, until I delved a little further and realized it's a rarity for home coffeemakers to meet these criteria. Additionally, other factors greatly influence your results, such as the total brew time and coffee grind size.

How to grind

Looking at coffee enthusiasts' blogs and even the commenters on our own coffee maker reviews and it's clear there's a passionate debate about whether to use blade grinders or more expensive burr grinders to process your coffee beans. Some argue that ordinary bladed grinders (also sold as spice grinders) can't chop their contents with the right amount of uniformity. They're also typically not adjustable.

Another theory about blade grinders is that the sheer kinetic energy unleashed by rapid slicing of the blades actually heats up the coffee particles -- essentially cooking them. This is said to alter the flavor (for the worse) of the final brewed beverage. I can't address this concern directly, but I can confirm that compared with beans ground in my personal spice grinder, the coffee I ran through an adjustable burr grinder (the Capresso Infinity Conical Burr Grinder, $100) was always the same size and texture. It's a huge difference from the inevitable bits of half-chopped beans I tend to experience using a basic blade grinder.

This irregularity can conceivably affect the surface area of coffee grounds exposed to water. And since grind size directly impacts how many coffee particles are extracted into the solution (the finer the grounds the higher the extraction), uniformity is essential to producing repeatable results. This is is why I always burr ground my test beans (Costco House Blend) at the medium setting.

Weighing and coffee-to-water ratio

I know for many out there splurging on a fancy burr grinder isn't an option. Trust me, I've yet to win this household spousal argument. That's why I strongly advise investing in a cheap kitchen scale (approximately $15 or £12). Whether you rely on a sophisticated burr grinder or are stuck using a basic bladed coffee chopper, the only way you'll know for sure how much grounds you're brewing with is to weigh it.

I also follow the SCAA guidelines and use 2 ounces of coffee per 45 ounces of water (57 grams per 1.3 liters). Keep in mind this water volume translates to roughly 10 French Tasse cups. Another benefit to weighing out your coffee grounds is that you don't have to mess around with those annoying coffee scoops many coffeemakers include with their machines. Not only are they grossly inaccurate since a "level" or "heaping" scoop can mean just about anything, they tend to be messy and hard to keep track of.

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Temperature and brew time are key factors in making tasty coffee. Brian Bennett/CNET

Temperature and brew time

As I stated before, the SCAA recommends that a home coffeemaker's brewing water reach the ideal temperature to properly whip up a tasty cup. Specifically the association says a machine's brew temp should hit 197.6 degrees Fahrenheit within the first minute brewing and not exceed 204.8 degrees. Also crucial is for a coffeemaker to expose its grounds to water between 4 and 8 minutes.

You'd be surprised how many kitchen gadgets overshoot this brew time, taking 8, 9, even 10 minutes or more to complete the brewing cycle. The same is true about mustering the heat to achieve the proper brewing temperature. This is why I measure the operating temperature within the brewing chamber of every coffee machine I review. I also time the entire brewing cycle of a given coffeemaker to confirm whether it meets (or how far behind it is from) the SCAA's guidelines.

Measurement and tasting

For the final bit of scientific testing we use a device called a refractometer. This gizmo relies on a lens to detect the amount of total dissolved solids (TDS) in coffee we brew, using distilled water as the control reading. As I said above, the SCAA says the ideal TDS percentage is between 1.15 and 1.35 percent. After testing numerous coffee machines, I'm inclined to agree.

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True coffee geeks use refractometers. Brian Bennett/CNET

As a matter of fact, the best products I've reviewed hit pretty much most if not all of the SCAA's standards. For instance my favorite gadget, the Bonavita BV1900TS , notched a brew time of 6 minutes (or under) and a TDS reading of 1.28 percent. The same goes for the Technivorm Moccamaster KBT 741 (1.2 TDS, 6 minutes). And for the record, coffee brewed with both products was consistently delicious.

When all's said and done

This is a lot of information to take in and I'm sure acting on these coffee brewing steps at home, especially in the early hours of the morning, is way too much to ask for. That said, I bet if you adopt even a few of these tactics, you'll be surprised by the positive results you can achieve.

I for one will never go back to the dim days of measuring out coffee grounds without a scale. And please, for the love of life, grind your beans as close to brewing time as possible.