When brewing coffee water temperature is crucial. The ideal range is between 195-205 degrees - remember, 212 degrees is boiling.
Every barista will have their own special formula for how to dial in whatever beans they have just right. For example, Vivace Espresso likes to dial in their coffee at 203.5 degrees.
If the water is too cold, you won't be able to extract the sought best oils and flavours of the beans.
On the other hand, if the water is too hot or you carry out the extraction for too long, you'll be left with a highly tani and bitter (i.e. overextracted) tasting coffee.
The golden ratio is a 18-22% extraction rate. You achieve that through a combo of heat and time.
The fineness of grind is another key variable as is the method of extraction. For example, when using a french press you'll want to steep your ground coffee for 4 ~ 6 minutes.
