#1. What Coffee are you using? Is it premium quality or is it something cheap being passed off as specialty coffee? Lower-quality coffees (most mass-produced coffees) tend to have increased bitterness. Did you purchase it at a Big Box Store? If so, your purchasing choice may be the root of the problem, sorry. Solution: Purchase coffee from an independent, reputable, artisan roaster. Nearly every town has at least one these days.
#2. When was the coffee roasted? Darker roasted coffees can become bitter when they get old. The oils on the surface of the beans interact with air and become rancid over time. Solution: Purchase coffee from an independent, local roaster or buy roast-to-order coffee on the web. Otherwise, you're drinking old coffee. It may be packaged to preserve flavor, using the best technology available, but it's still not fresh, and there is a profound difference.
#3. How dark is your roast? Dark roasted coffees, coffees labeled as Italian or French Roast are going to have some bitterness resulting from the carbonization that occurs late in the roasting process. Think of a marshmallow roasting over a campfire. A carefully roasted, golden brown marshmallow has a different taste than one held too close to the flames and charred. Solution: If you take your marshmallows golden and toasty brown, try a light, medium, or medium-dark roast.
#4 Over-extracted coffee (undesirable amounts of dissolved solids in the cup).
A. Grind too fine? When coffee is ground too fine for the chosen brewing method, the water cannot flow properly, resulting in excessive bitterness.
B. Steep too long? Steeping coffee longer than five minutes in a French press or other immersion brewer can create an over-extracted, bitter cup. Electric plug-in coffeemakers often take too long to brew, resulting in an over-extracted and bitter cup. Solution: Match the grind to the preparation method: medium for drip, coarse for press pot. Solution: Thoroughly clean all coffee-making equipment. Built up old oils and gunk can add to bitterness. Calcium buildup inside automatic coffeemakers can result in longer brew times which can increase bitterness.
C Water too hot? Ideal Brewing temperature is 198-202 degrees. Using water at a rolling boil can create an over-extracted, bitter cup. Water below ideal temperature creates an under-extracted, sour taste.
D. Too much ground coffee? Use of too much coffee impedes the flow of water and leads to excessive dissolved solids in the cup, which can be perceived as bitter.
E. Finally, external factors such as illness, change in diet, toothpaste, and certain medicines can affect how we perceive bitterness (think of drinking a glass of orange juice right after brushing your teeth).