Good coffee: it’s science, not art.

Good coffee does not occur out of love or eye measurments based on “experience”. Good coffee is a result of precision and discipline. – Tim Wendelboe

The whole idea that there is a craft to making coffee is a load of codswallop.  Saying it is an art is simply a vague disguise for laziness.  As with any food stuff, you are reliant upon many variables from coffee plant to coffee cup, but if you have a good foundation of the basic principles of coffee brewing and a basic understanding of scientific principles, there’s no reason why you should be making bad coffee.  With that being said, here are some basic principles of coffee brewing:

Image from Behance.net – Glennz Tees Designs

• Understand the process:  Different brewing methods require changes to the variables for coffee brewing.  Generally speaking, filter brews are better with a coarser grind, and light roasts, whilst espresso is better with a darker roast and finer grinds.  These differences apply also to extraction and steep times, weights and water to coffee ratios.  This means that you should not be surprised if your coffee tastes like rubbish if you run an italian style roast through an aeropress.
• Cleaning isn’t optional: It doesn’t matter what process you are using, you need to keep your gear clean.  A mate of mine insisted that the best tea cup is one that has the tannin stains inside, because it adds ‘extra flavour’, however if you do this with your coffee equipment, all you will end up with is bitter, rancid coffee.  Cleaning should be conducted after every brew (if possible) as oil residue is left behind after each extraction.  If your coffee equipment is left uncleaned it can lead to contamination of new brews and leave undesirable flavours.
• Get the right equipment: The essentials are thermometers, scales and a burr grinder.  Not having this equipment won’t ruin your coffee, but you are relying far more on luck to brew a decent coffee.  Make sure you have the correct cleaning products,  and for espresso machines a good quality tamper and blind filters are very important.  Decanting vessels and aerators (those used for wine) are some other handy pieces of kit.
• Rubbish in = rubbish out: The coffee beans and water quality you choose to brew with will have a direct and noticeable effect on the quality of your brew.  If you love coffee, then it is worth spending the money getting coffee from a roaster who uses direct-trade model. The quality of the green bean has a huge influence on the quality of the roasted product.

Here’s where the science part comes.  Essentially the scientific method involves coming up with a testable question (hypothesis), and then testing that question in a controlled experiment.  In the end, a making a cup of coffee is nothing more than a chemical reaction and therefore the parameters of that reaction can be adjusted to change the end result.  So if you are making coffee you are unhappy with, start by identifying  the variable in your brew process.  There should be some that you can control for immediately, such as the cleanliness of the equipment, as well as the quality of the produce and water.  The variables you have left to play with are the amount (weight) of coffee, grind particle size, extraction time, extraction pressure and water temperature.  So all you have to do is go through a process of keeping four of the variables consistent, and change the fifth.  Make a cup of coffee with the change and see what happens.  To be really nerdy, take notes in a book so you can keep track of what changes you have made, but in the end if you get something you think tastes good it’s well enough to just try and remember it.

In the end, if you take the time and care to ensure you are being precise with the way you are brewing coffee, you should never end up disappointed from a cup of coffee.