How to Properly Measure and Adjust Mash pH

Mash pH has caused a lot of confusion in the homebrewing world. So much that even some experts have made some questionable remarks on what is correct and what is not. I’m writing this because I recently had the same problem. I did a lot of research on mash pH information and got a lot of conflicting answers. It gets even more confusing when you read about how mash pH differs in the actual mash vs the cooled wort sample. It’s enough to make your head spin.

I’m actually glad I had this problem because it helped me understand the issue first hand. I was able to sort all of this out with the help of other homebrewers who have a far more in-depth understanding of this topic than I do. Hopefully this will help anyone who has the same questions as I did.

Ideal Mash pH Range

Before I jump into anything, it’s important to understand that mash pH is measured at room temperature, not the actual hot mash. The optimal mash pH of 5.2-5.6 is referring to the room temperature measurement.

This was initially incorrectly published in a BYO article and caused a slew of backlash. The ideal mash pH target range for a cooled wort sample has historically been 5.2-5.6. So when a mash pH figure is given for a specific style of beer, let’s say 5.4, that number is referring to the cooled wort sample, and not the actual hot mash temp, which could actually be a lower number. The true difference in variance is debated, but as far as I’m concerned it only adds confusion and isn’t really needed.

Why Mash pH Matters?

Mashing in the ideal pH range helps to promote better conversion, a cleaner finish, and a more balanced overall beer. If you make no pH adjustments, your pH is likely to be higher than the recommended range of 5.2-5.6. pH is commonly adjusted (decreased) with either lactic acid or phosphoric acid.

Predicting Acid Adjustments

The difficulty with making any acid adjustments in the mash is the actual timing of it. Mash pH cannot be accurately measured until 10-15 minutes into the mash. If you wait until this point to make any initial acid adjustments, it could actually be too late, as the conversion process is already underway. To get around this, we need to use brewing software to predict what our mash pH will be, so we can actually make acid additions before we dough in.

How and When to Measure Mash pH—My Process

Measuring mash pH

I estimate my mash pH using BeerSmith (others user Bru’n Water). These programs take into account the recipe’s grain bill and water profile (water and salts) to estimate mash pH. If you already use BeerSmith or want to try it out, here is a video of Brad Smith giving a tutorial on how to calculate mash pH adjustments with BeerSmith. It’s honestly really simple once you get the hang of it.

  1. I follow Brad’s recommendation to add 80% of my suggested lactic acid addition directly to my heated strike water before I dough in.
  2. I dough in, add my brewing salts, stir the mash thoroughly, and set a timer for 60 minutes.
  3. Once 10-15 minutes have passed (and no sooner), I pull a sample of my wort and cool it to around 70°F. I use my Apera Instruments digital pH meter to take a reading and record it. If it’s within the acceptable target range I want, I continue to mash for the remaining duration. You can make further adjustments if needed by adding more or the remaining 20% lactic acid.

The reason for adding only 80% of acid upfront is to reduce the risk of overshooting your target. Raising mash pH is another story I don’t have enough experience with to honestly provide advice. Brewing software isn’t perfect and should serve as a rough estimate, so it’s better to err on the side of caution. If you’ve brewed the same recipe several times, and have a better understanding of how much acid is really needed, you can of course add all at once.

To hit this home one more time, pH figures in BeerSmith are based off cooled wort samples!

A Word of Caution on 5.2 Mash Stabilizer

I’m sure many of you have heard of the 5.2 Mash Stabilizer product. I have never used it but I’ve of course heard rumors that it does not work. To be completely honest I have no idea how it possibly could work. There are so many factors that go into mash pH that I cannot possibly imagine a one size fits all solution to get mash pH to 5.2 every time. Starting water profiles and different grains all have different impacts on your mash pH. You’re much better off doing it the right way as it’s really easy once you understand the process. Don’t waste your money!

References and In-Depth Articles

Below is more content on mash pH from people who really understand what they’re talking about at a technical level. If you would like to dive into more in-depth knowledge and advice I would read these articles below.

AJ Delange:
Matt Brungard: 
KAI Troester: 

2 thoughts on “How to Properly Measure and Adjust Mash pH

  1. Nice article, however I must ask why the contradiction on acid additions?
    You first say:
    “Mash pH cannot be accurately measured until 10-15 minutes into the mash. If you wait until this point to make any initial acid adjustments, it could actually be too late, as the conversion process is already underway.”

    Which I understand and adhere to in my own brewing, but later you say:
    “You can make further adjustments if needed by adding more or the remaining 20% lactic acid.”

    I’m not quite sure I understand?

    1. The bulk/all acid adjustments should be made as soon as possible. All that means is if you’re still off after your initial adjustment at mash in, then you can test it at the 20 minute mark and make any final adjustments if you’re still off. Not ideal but better than nothing. This is good advice from Brad at BeerSmith.

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