Water alkalinity and the mash pH

[Leard]

So far I've relied on the water treatment for beginners post on here and have found it incredibly useful. Using lactic acid, gypsum, calcium chloride, bicarbonate of soda, and Campden tablets I've been able to successfully treat my beer.

However on Beersmith it mentions mash pH. Something that I haven't really paid attention to. I simply just measure my water's alkalinity and adjust accordingly. However my understanding is that mash pH can also be adjusted using acid, such as lactic acid that I use to bring alkalinity down. So how do mash pH and alkalinity relate to each other? Should I be adjusting my water's alkalinity pre-mash, and then during the mash measuring the pH and adding more lactic acid to bring it down?

 

[strange-steve]

Alkalinity adjustment isn't done just for the sake of having a specific amount of alkalinity in the water, but rather is the means by which we achieve a proper mash pH. The two are intrinsically linked because the pH of the mash will be largely (but not exclusively) determined by the alkalinity of the water. Alkalinity resists change of pH, so if it's too high then the pH won't fall enough, if it's too low the pH will fall too much. If we get the alkalinity right then the pH will fall into the correct range (around 5.4 give or take a couple of tenths).

You can measure the mash pH to check if you've got it right but adjusting the pH mid-mash probably isn't ideal (unless maybe it's a long way off) because it's very difficult to determine exactly how much acid/base you'll need to make the correct adjustment at this point, plus each time you make an adjustment you'll need to stir it in, take a sample, cool it, and then measure which all takes time. By the time you've taken a couple of samples, conversion is probably mostly done anyway. It might be better just to take notes and adjust for next time.

 

[Leard]

So should I just continue what I'm doing with the adjustment of the alkalinity with lactic acid and bicarb soda, and then check the water pH before I start the mash?

 

[RichardM]

So should I just continue what I'm doing with the adjustment of the alkalinity with lactic acid and bicarb soda, and then check the water pH before I start the mash?

No, you check the ph ten or fifteen minutes in the mash