What is it that makes the perfect cup of coffee? Is it the roast, the origin of the beans, the music playing while it is brewed? Believe it or not, there have been countless studies on this very topic.

In 1920, the National Coffee Roasters Association tasked Professor Samuel Cate Prescott of MIT with determining what made the best cup of coffee. They provided Prescott with $40,000 (keep in mind this was 1920) to set up a laboratory with the sole purpose of perfecting coffee.  Along with his duties as Dean of Science at MIT, Prescott spent three years determining what went into the perfect cup of coffee.

Prescott determined that the perfect cup of coffee was one tablespoon of ground coffee for every eight ounces of water. The water should be almost to the point of boiling, without actually reaching a boil. A glass or ceramic container should be used to heat the water, so as to eliminate the chance of the metal flavoring the water. The coffee should never be boiled, reheated or reused, according to Prescott’s tests.

So, is this the only way to obtain the “perfect” cup of coffee? Not necessarily. I have seen later studies that have modified the recipe as much as to say that the recipe should be as much as two tablespoons of coffee for every 6 ounces of water. This test postulated that the best flavor comes from this recipe, however the coffee is very strong. According to this study, if you want a weaker coffee, you need to add hot water after the coffee has been brewed to achieve the desired strength.

The reason the recipe varies so widely in different studies is because people vary widely. However, there are a number of things that studies tend to agree on across the board: water, grind, temperature, filter and freshness of beans.

Water

The water should have impurities filtered out. You have to remember that any flavor that exists in the water will show up in the brewed coffee. If your tap water is heavily chlorinated, your coffee will end up tasting like you brewed it with bleach water. If there are a lot of minerals in your water, the mineral flavor will show up in your water, and the minerals can end up clogging the inner workings of your coffee pot.

Grind

Grind is quite possibly the most important, but overlooked, aspect of brewing coffee. If you use a Turkish grind in a percolator pot, you will end up with a cup of wet grounds. On the other end of the spectrum, if you put use a course grind in an espresso machine, you will end up with some slightly tinted hot water being dispensed.

Most home coffee pots use either a cone or flat bottom filter. The cone filter will require a slightly finer grind than the flat bottom filter, unless it is a metal filter. Metal filters tend to take a medium-course grind wether they are cone or flat bottom.

The biggest problem people have with the coffee grind is the grinder itself. Most people who brew coffee at home either buy ground coffee or grind it in a rotary grinder (the kind with the blades that spin around like a food processor). Rotary grinders help you to keep the coffee fresher, but they don’t grind the coffee to a consistent size. While buying pre-ground coffee solves the problem with grinding the coffee to a consistent size, freshness becomes an issue.

So, what’s the best solution for grinding your beans? You need a burr grinder. These grinders use rotating discs with blades that crush the beans to a consistent grind between the disks (burrs). The good news is that home burr grinders have drastically dropped in price the past few years. My first burr grinder, almost 10 years ago, was bought on sale for $75. I now own a much better quality burr grinder, which I purchased in the last 6 months for about $30. Even the cheapest rotary grinders I have seen recently are $22, which means that to get good coffee only takes an addition $7 when you purchase your grinder. A worthy investment if you ask me.

Temperature

How hot should the water be when it hits the coffee grounds? Officially, the water should be “just off the boil”. Coffee pots range in temperature from 198 degrees to 205 degrees fahrenheit. If you are using a coffee pot, you just have to trust that the pot you are using is within this range. However, if you are using a method such as a pour over filter or a press pot, you will need to be sure you are getting the coffee to this point. Obviously, a well calibrated thermometer will be your best source for determining the temperature of your water, but this isn’t the method most of us will be using.

If you heat your water for your coffee in a tea kettle, pan on the stove or in a microwave, you are able to use water that is the right temperature without the hassle of a thermometer. By bringing the water to a boil, you know you have reached the proper temperature, and then some. Obviously, you don’t want to pour it right over the grounds, as this will result in a burnt tasting coffee. The best option here is to let the water sit for about 1-2 minutes away from the burner or microwave. This allows the water to cool from 212 degrees to closer to 200 degrees.

Filter

With so many filter options available, what is the best type to use? The long accepted standard for perfect coffee is the press pot. This uses a form of a metal filter. If you just want an easy clean up, there isn’t necessarily anything wrong with using a paper filter. Although, the paper does prevent the coffee oils from making it to your cup. The oils are the most flavorful part of the coffee, so by using a paper filter, you are eliminating some of the best parts of your coffee flavor.

The problem with a press pot is that it can be much harder to clean. The filter is usually at least three layers, and grounds have a tendency to get caught in the layers. If you don’t have a press pot, or don’t want the hassle of cleaning one, your best option would be to buy a metal filter. These require a little more cleanup than a paper filter, but I think you will immediately be thankful for the switch.

Freshness

Fresh coffee is the single biggest factor that affects the final flavor of the coffee. When I refer to freshness, it’s not just how old the pot of coffee is, it’s also how long it’s been since the beans were roasted or ground, and even when the pot was last cleaned.

Stale beans make stale tasting, flavorless coffee. The best way to store your beans is in an airtight, opaque container, and avoid extreme temperatures. Here in Phoenix, a cabinet on an exterior wall is a horrible place to keep coffee, because the sun has a tendency to heat these cabinets to unacceptable temperatures. It can also ruin your beans to store them in the freezer, despite how common this practice is. I have even toured a roasting plant that stored beans in a freezer to store them until they are delivered, but common practice doesn’t always mean best practice.

It is also important to keep your coffee pot clean. The oils from coffee go rancid, and can cause your coffee to taste especially bitter. You should wash any removable parts in hot water with a mild detergent, and rinse well, every day. Once a week, you will also want to clean your coffee maker with a coffee brewer cleaning solution. You can use a distilled white vinegar, but your whole house will smell like hot vinegar.

Finally, old coffee can also have rancid oils. While old coffee isn’t going to make you sick, it just doesn’t taste good. Even if you refrigerate your coffee, you will want to be sure to mix milk into it right away, or use up the coffee within 12 hours.

The fact is, the best cup of coffee is the one you like the best. I like my coffee strong, but I know others who don’t want the full flavor of coffee, even if it has been watered down after being brewed. For these people, they may like their coffee better at the one tablespoon to eight ounces of water recipe, while I use the two tablespoons to six ounces recipe. Experiment with your coffee, change it up from time to time. Who knows, you may even find a recipe and roast that you can drink black, rather than loaded with cream and sugar.