The Filter: Dual Functionality

A lot of folks will ask me which filter is the best one for them to use in their coffee makers at home and/or at work. To best answer the question, it's necessary to first describe the essential functions of the filter, there are TWO of them.

The first function of the filter, obviously, in the case of the drip coffee maker, is to hold the coffee grounds and keep them from entering the pot with which you will be pouring from. This is obviously a critical function, but the other and equally critical function, is to hold the water in the filter with the coffee grounds for the proper length of time for brewing before allowing the water to be released in to the pot below. Your filter acts as a fixed timing governor, which determines the length of time that the coffee brews before passing completely through the coffee grounds.

If you think about it, if there was no filter, and the coffee grounds were held magically in mid air by a filter made of thin air (stay with me on this one), and you poured your water in to this filter, the water would just fall right through only being held up by the coffee itself. It would barely extract any coffee beverage before basically falling right through. Now, the other extreme, say you had a filter made of solid plastic. A plastic baggie full of coffee grounds. Pour in the water, and obviously, way over extracted coffee due to the fact that the water could not pass through at all. You'd be left with a baggie full of horribly bitter, gritty… you get the idea.

So enter the sweet spot. Your filter not only holds the coffee grounds back, but also acts as a fixed timing element to make sure that the water remains in contact with the coffee grounds for the perfect amount of time for the perfect extraction of your coffee. Not under extracting (weak, thin coffee), not over extracting (bitter, harsh coffee), but that sweet spot right in the middle, the sweet spot that represents pure coffee euphoria.

Now consider this… your coffee filter is a fixed medium, right? It's size does not change, therefore the amount of time that water passes through it is constant. Your brewer heats the water in a consistent amount of time (hopefully that is, keep it clean with CleanCaf), your filter allows the water to pass through consistently, then what's the variable? There still is something that can affect how long the water remains in contact with the coffee. The answer? The coffee itself!

Your coffee's particle size, after being ground, in relation to the filter being used, will determine how fast the water passes through the filter as well. Grind to small, and the coffee will clog the filter and you've got a huge mess. Grind to large a particle size, and you risk under extraction, weak thin coffee. Enter again, the sweet spot in grind particle size. Grinding your coffee inconsistently throughout the dose (amount of coffee used per brew cycle) affects the taste of your brewed coffee. Grind too small, and you risk over extraction and clogging your filter, grind too big and you risk under extraction and weak coffee.

All of this is precisely why we ask our customers what filter they are using in their brewers, so that we can grind precisely for the sweet spot for their coffee machines. This is also why we suggest a burr grinder over a blade grinder, blade grinders can be inconsistent due to the length of time the grinder runs is determined by how long you hold down the button. Most blade grinder users simply hold the button until "they can hear when it's done". The burr grinders are fed by gravity, and the coffee will not pass through the burrs until they are the proper size.

So to answer the original question, which is the best filter to use?

That depends on your taste. Or rather, how you like your coffee to taste. The two options really, for the common drip coffee maker, is a paper filter, or the gold toned metal filter.

The paper filter is a finer filter size, catching a lot of the micro sized solid coffee particles that the metal filter will allow to pass through. The paper filters then, will produce a cleaner, thinner coffee with less body (weight, or thickness) than the metal filter.

The metal filter, on the other hand, will produce a heavier, full bodied coffee. It will allow more of the tiny coffee solids to pass through to the pot, for a much fuller flavor experience, therefore leaving a little bit of grit in the bottom of the pot.

In summary, the paper filter gives you a cleaner, thinner cup, and the metal filter will give you a fuller, more flavorful cup. So, which filter is best for you is up for you to decide based on your taste preferences!

(c) Copyright 2007 Cobblestone Coffee Roastery, LLC. Reprint by permission only.