ArticleHow to Make a Sour Mash As any all-grain brewer knows, a mash is a mixture of hot water and grain. A “sour mash” is a mash that has acid-producing bacteria in it. Most people associate the termAlready a member? Log InWritten by Chris ColbyIssue: September 2000You'll Also Like Article MEMBERS ONLY Points Off? Defining gravity and why it matters Homebrewers have been known to fret over their brewhouse efficiency numbers. Make sure you know the differences, the variables involved, and how to troubleshoot. Article MEMBERS ONLY The Role of pH in Brewing pH plays a role in every step of the brewing process — from the time you mash in, all the way through to the final beer that fills the glass. Take a closer look at pH throughout the brewing process.