Being a beginner, I always have questions about water chemistry. I've been using that 5.2 buffer product, because it seems the "safe" way to keep my mash pH in the correct area. If I could attempt to correlate that product to this example - would that be like adding a very thick vessel right at the 5.2 pH level, thereby requiring a great amount of either an acidic solution or alkaline solution to change the pH?
Yeah, the 5.2 stuff. Don’t get me started on that
Well, you did. 5.2 is not a buffer in the correct sense of a pH buffer. And if it is, it is a very weak buffer. I have done a number of experiments with it and it doesn’t work as advertised. First off, it is made with phosphate salts (namely sodium phosphate) and using the recommended amount boosts your beer sodium content by 100 mg/l. Not really a problem when your water is low in sodium.
Secondly, phosphate salts are not good for forming a good buffer at 5.2. This is because there is no “bulge” at 5.2 for phosphate. The “bulges”, i.e. pH ranges for good buffering for phosphate are at 3.1-4.1, 6.2-8.2 and 11.3-13.3.
Since it is not a good buffer it does little from keeping the pH from falling too far. Although it is not a common problem in brewing it is an indication that this product doesn’t work as advertised. With respect to keeping pH from rising it doesn’t seem to buffer the pH at 5.2 but it seems to “cap” the pH at 5.8. This means using this product prevents your pH from rising too far which might be why this product seems to work when brewers use it. This effect may come from calcium and phosphate reactions and not the buffering action of the phosphate. I haven’t confirmed that yet.
If this product makes a difference for you I recommend spending the money on a Ward Labs water test or buying a GH&KH test kit to do your own simple water test. With that information you can figure out simple water and/or grist modifications that allow you to get your pH into the appropriate range w/o having to add a lot of sodium.