I’ve had an espresso machine for almost a year now and have used the same process since first getting it down pat shortly thereafter. However, recent attempts have resulted in a very bitter tasting espresso, which is uncharacteristic.

We’re using the same brand and type of grounds, the same timing, the same amount of tamping of the grounds, the same amount of coffee. We clean the machine to the manufacturer’s instructions each time we use it, and use fresh water each time we brew.

Any idea what would cause this change?