Once you’ve mastered control over fermentation temperature and yeast health, study the effects of water on beer quality, and it will help you understand the difference between a good beer and a great homebrew. Water is often neglected, even though it is the foundation upon which beer is built. It greatly affects not only the final character of the beer, but also the entire brewing process.
In extract brewing, you get the minerals from the extracts themselves (that is, from the water they were originally brewed with), and then the water you use adds more minerals. You’ll have a hard time figuring out what you’re working with, so in extract brewing there’s not much point in adding mineral salts. With grain brewing, on the other hand, you’ll be using tap water or building a water profile from scratch, which means you’ll have more control over the situation.
First, you need to understand what’s in your water. The main things to look at are calcium content, magnesium to chloride ratios, and hardness. In addition, make sure that the content of other ions is below a certain threshold. Chlorides and sulfates should generally be below 250 parts per million. In water chemistry, pH and calcium are especially important.
Once you feel comfortable, you can start making changes and see how it affects your finished beer. Understanding how water works will help you take a big step in understanding how raw materials and techniques affect beer.