How Much Gypsum Does It Take To Lower Mash Ph? 4 Tips

Mash pH is a crucial factor in the beer brewing process. You can adjust the mash pH by adding salts to the water or mash. One of the most popular salts for this purpose is gypsum.

You will need about 0.5-2 tsp of gypsum to lower your mash pH. The exact quantity should be based on your water parameters. You can also add gypsum ½ tsp at a time, mix it in and measure the pH after each addition until it matches your desired value.

If you’re struggling to make your mash pH lower or higher to meet the optimum of 5.2-5.6, I’ll give you four useful tips for adjusting the mash pH in this article. But before that, I want to talk a little bit about adjusting mash pH using gypsum and other salts.

Adjusting Mash pH Using Gypsum and Other Salts: An Overview

Although gypsum, also known as calcium sulfate, is a good way to adjust pH, it’s not the only way. You can use other salts to increase or decrease your pH value. Let’s discuss the possible options and learn how to measure the right amount of salt you need.

The best way to start this discussion would be to grab a copy of John Palmer’s book How To Brew: Everything You Need to Know to Brew Great Beer Every Time (available on Amazon.com). It shows what salts can be used, their effect on pH levels, and two other metrics that will determine their required quantities.

Brewing Salt and Common NameConcentration at 1 gram/gallonGrams per level teaspoonEffects
Calcium Carbonate(CaCO3)a.k.a. Chalk105 ppmCa+2158 ppm CO3-21.8Raises pH
Calcium Sulfate(CaSO4*2 H2O)a.k.a. Gypsum61.5 ppmCa+2147.4 ppmSO4-24.0Lowers pH
Calcium Chloride(CaCl2*2H2O)72 ppmCa+2127 ppmCl-13.4Lowers pH
Magnesium Sulfate(MgSO4*7H2O)a.k.a. Epsom Salt26 ppmMg+2103 ppmSO4-24.5Lowers pH by a small amount
Sodium Bicarbonate(NaHCO3)a.k.a. Baking Soda75 ppmNa+1191 ppmHCO3-4.4Raises pH by adding alkalinity.

Tips on Measuring the Right Amount of Gypsum

Before I go into detail about your options for lowering mash pH, let’s first talk about how much of the chosen salt you need to meet your goal.

Tip 1: Easy Does It — Go ½ Tsp at a Time

The most straightforward method is to add the gypsum in small quantities — ½ or even ¼ tsp at a time — while mixing the mixture in between the additions and measuring pH until it is at the proper level.

While measuring salts this way is easier than doing actual calculations, it comes with a higher margin for error. If you add too much of most salts that can be used to adjust your mash pH, they can hurt the quality and flavor of your beer.

If you want to be more precise, I’ll go into another method to help you come up with more reliable numbers.

Tip 2: Measure the Differences in Concentration

This one is a little more difficult than what I just described above. However, with enough practice, you can easily grasp it and improve your home brewing skills.

First, determine the difference between the current concentration of calcium and the ideal concentration required for your mash. You can use an online calculator for this purpose. 

To make sure the calculations are accurate, you need the necessary information regarding alkalinity, calcium, and magnesium concentrations.

Next, calculate how much of the salt of your choice is required to reach the desired calcium level. 

Here’s how you can do it using the table I provided earlier:

  1. Take the ‘Concentration at 1 gram/gallon’ value for Ca for the salt of your choice. For example, let’s take the value for gypsum, which is 61.5 ppm.
  2. Divide your difference in concentration by 61.5 ppm. This will give you the amount of salt you need in grams per 1 gallon of water.
  3. Multiply the value you have by the gallons of water in your mash.
  4. Convert grams into tsp for your convenience. Take the value you have in the previous step and divide it by ‘Grams per level teaspoon’ from the table. For gypsum, it’s 4.0.

As you can see, the process is rather straightforward. You can choose not to count the values manually and use calculators instead, but it’s always best to understand how the process works.

Tips on Choosing the Right Salt for Adjusting Your Mash Ph

Now that I’ve shown you the mathematical aspect of measuring pH (whew!), let’s discuss when to use gypsum and in what instances other salts can be more useful. By learning more about the benefits of each method, you can make the most of them.

Tip 3: Keep an Eye on the Sulfate

When choosing the salt for adjusting your mash pH, pay attention to the sulfate and chloride levels. The average numbers for brewing water are 50-150 ppm of sulfate and 0-150 ppm of chloride. To understand these numbers, I’ll need to go back to the math for a minute.

For example, you’ll notice that when counting the required amount of gypsum, you only used the ‘Concentration at 1 gram/gallon’ value for calcium. 

If you take the value for sulfate and count the resulting sulfate concentration the same way it was calculated for gypsum, you’ll get an additional 368 ppm, which is clearly too much.

For those reasons, you can’t always go for gypsum. It’s better to consider using another salt or combining different salts in optimum amounts.

Tip 4: Choose the Most Beneficial Salt

The best way to approach the adjustment of your mash pH is to analyze all factors and choose a salt that will benefit you the most. 

Here are some simple tips for doing that:

  • Gypsum: Use this to reduce pH if the sulfate level is low.
  • Chalk: Use this to increase pH in dark beers.
  • Calcium Chloride: Use this to reduce pH if the chloride level is low.
  • Baking Soda: Use this to increase pH and add alkalinity.

Final Thoughts

If you’re looking for a way to lower your mash pH, there are many factors you should keep in mind. To achieve the greatest quality for your beer, you should know how to count the amount of gypsum required, consider other salts, and maybe use a home brewing kit too.

About HomeBrewAdvice

Hello, my name is Simon. Together with a group of writers I write about brewing beer and making wine. We all share a passion for the great things in life, such as making stuff from scratch.

The business of HomeBrewAdvice is to bring you great information, stories and product reviews from brewing at home, and making wine


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