The relationship between Residual Alkalinity and pH

[mgeorg04]

I have spent several days and hours studying water chemistry with brewing, but I am still struggling with finding answers about residual alkalinity. John Palmer puts a lot of emphasis on having the correct RA, but it seems he sets the correct RA in order to reach the desired pH range.

The reason I am concerned is because Bru'n Water and EZ water calculator give me pH results within range after a few salt additions, but show RA in the negatives every time...sometimes as much as -150. Is this cause for concern, or should I only care about mash pH?

Virginia Beach water is soft with very low alkalinity, so it is not ideal for darker beers. If I brew darker beers, and the malts added to those spreadsheets show I will be at the correct pH but with really low RA, is that still a problem? Each time I attempt to correct the RA, while keeping pH in the range, the calcium, sulfate or chloride levels go through the roof.

I assume this is a result of my lack of knowledge with the subject. I just want to be sure I am OK with negative RA results on every beer style (pales through stouts) as long as pH is where it belongs.

Here is my water profile if anyone is curious:

Calcium: 16
Magnesium: 3
Sodium: 12
Chloride: 18
Sulfate: 34
Alkalinity: 22
pH: 7.3

 

[helibrewer]

I am far from an expert, but I focus on pH and don't pay much attention to RA. I use RO water so I am in the same boat as you are as far as little alkalinity goes.

 

[user 141939]

I have similar water to you and also use bru'n water. I typically just add a small amount of cacl2 and gypsum to get my calcium levels above 50 and then add baking soda to correct for pH if I am making a dark beer.

By following this approach I usually have a small positive RA as a result. I've never needed to add too much, usually no more than 0.5 grams per gallon of anything to get where I need to be. I also don't pay much attention to the RA. I look more at PH, and sulfate/chloride ratio. I also don't know if I should be paying more attention to RA or not.


Sent from my iPhone using Home Brew

 

[MrHadack]

The reason I am concerned is because Bru'n Water and EZ water calculator give me pH results within range after a few salt additions, but show RA in the negatives every time...sometimes as much as -150. Is this cause for concern, or should I only care about mash pH?

Alkalinity is the water's ability to buffer against efforts to lower its pH.

Residual Alkalinity is the amount of alkalinity (buffering ability) left over AFTER the malt reacts with the water.

So as long as your predicted mash pH is right where it should be, it doesn't matter if the RA is negative. It's just indicating that the water is way past the point where it could further buffer against a drop in pH.

So when using sheets like Bru'n Water, I typically add my grain bill to the mash acidity page, add enough calcium to get up to 50 PPM (which according to some research isn't needed) and then modify with acid or other salts to raise or lower the pH to the right spot. My RA is typically negative as well.

 

[mabrungard]

RA is not a parameter that matters. However, when mashing a pale grist, it is possible that a significantly negative RA will be produced in order to reach the desired mash pH.

 

[mgeorg04]

Thanks everyone for the replies. MrHadack, I had a feeling RA was, in a way, a result of the reaction of the mixture in the mash. Reading through all the discussions online it just wasn't very clear until you dumbed it down for me.

I think John Palmer's excel spreadsheet brought on these questions because he seems to have you target an RA before the mashing process, which confused the hell out of me. It all makes sense now, and it really is simple now that I am able to grasp it.

Thanks again!