pH, short for potential hydrogen, measures the acidity or basicity of a brewing fluid such as the starting water (liquor), mash, wort, or beer. A fluid with a pH less than 7 is acidic, and a fluid with a pH greater than 7 is basic or alkaline. If a fluid has a pH of 7, such as pure water, then it is considered neutral.
pH is a very important factor in all grain brewing, and different geographical areas and water sources can have dramatically different pH levels and mineral contents that impact the pH of a mash. Additionally, the style of beer that you brew will have a significant impact on your mash pH level. Typically the darker the color of the malts that comprise your grain bill, the more acidic your mash will be. This is important because the enzymatic conversion of starches to sugars only effectively occurs in a mash that has a pH between 5.0 and 6.0; ideally your mash would be between 5.2 and 5.5 pH, which is considered optimal.
A great starting place for dialing in your mash pH is to get a copy of your municipal water report to learn about the pH and mineral composition of your brewing water. Software such as BeerSmith has great tools built in that will help you determine when brewing salt and mineral additions are required to help you bring your pH in line when comparing your local water to that of a specific style of beer. Lastly, purchasing some inexpensive pH testing strips is an effective way to ensure that your mash pH is at an appropriate level.
A wide selection of home brewing pH testing equipment can be found here:
Calcium chloride or CaCl2 is used as water additive to reduce the pH of a mash. One gram per gallon typically adds 72 ppm of calcium and 127 ppm of chloride, but you will want to verify those numbers with your vendor.
Calcium carbonate or CaCO3 is precipitated chalk. It is typically used in brewing as a water adjustment to increases the pH of a mash. You will want to verify with your vendor, but 1 gram per gallon usually adds 106 ppm calcium and 158 ppm carbonate.
A buffer or buffer solution, as related to pH, is typically a solution consisting of a weak acid and its conjugate base, or a weak base and its conjugate acid. The purpose of the buffer is to decrease the impact to pH when a differing acid or base is introduced to the solution.
PH plays an important role when it comes to a brewer’s mash. You will find brewing pH stabilizers available on the market, such as pH Stabilizer 5.2, which is a sodium phosphate salt-based buffer; please be aware that there is a great deal of disagreement about how beneficial or detrimental they actually are. Ideally, you would control the mash pH of each individual beer style by comparing your home water profile to that of the desired water profile of the beer you are brewing, and make the appropriate water adjustments that way.
Additionally, some of the popular home brewing software on the market will also help you determine the proper water additives based on the estimated pH level of the grain bill that you are brewing with. Lastly, there are a variety of pH measuring strips and meters available on the market, which can help you determine if adjustments need to be made to your mash.
In very simplified terms, alkalinity refers to the pH of a solution registering greater then 7 and its capacity for neutralizing an acid solution. In order to boost the alkalinity in a mash and offset acidity, you would most commonly add a carbonate or bicarbonate such as chalk\calcium carbonate.