Very helpful, thanks.
Here’s a rabbit hole or two:
For the record, I tend to agree with Ashton Lewis on this one, even though millions of homebrewers didn’t understand and/or will choose not to agree. I thought he made a decent attempt to gather references. Silver and others took the discussion to higher levels on HBT. I’ll see if I can find some more rabbit holes. Ah… heh… here, look at these:
https://www.homebrewersassociation.org/forum/index.php?topic=6168.msg74839#msg74839
https://www.homebrewersassociation.org/forum/index.php?topic=4739.msg56010#msg56010
In my own personal experience, measuring pH at mash temperature for a while now… I know that in my own brewing, pH tends to read 0.20-0.25 lower in the mash than at room temperature. But specific variables also do matter, so, as with so many things in brewing, YMMV.
EDIT:
Ahh… here’s the BIG one:
Thanks very much, dmtaylor. These links are enlightening reads. I will be tweaking my next few batches to shoot for a higher room-temp mash pH (i.e. 5.6-5.7), to see what if any difference it makes. Thanks again.
Be sure to adjust to a target of 5.1-5.2 pH post boil and cooling, and do so before or during the boil.
This is making me wince a little because I thought that the desired pH of the boil was around 5.5 (Kai had some things like this on his site). I am doing 30m boils so I boil for 20 minutes in the mid-5s and then with 10 minutes left I adjust the boil with an acid addition which is supposed to make whirfloc more efficient. The beers I have been doing this on are coming out very nicely and my clarity is better too. The “during the boil” part sounds reasonable but the “before the boil” sounds like the boil would take place at a pH that was too low… or is there no “too low” when it comes to the pH of the boil?
The higher the pH going into the boil, the greater the pH drop observed across the boil. An ~0.30 pH drop across the boil for the case of entering the boil at ~5.8 pH (room temp) dwindles to a pH drop of ~zero across the boil for the case of entering the boil at a pH of ~5.0 (room temp). The often parroted presumption of a fixed 0.30 pH point drop anticipated across the boil is highly flawed. I speculate it to have been ‘potentially’ derived from test mashes (Congress Mashes) involving only what is most likely to be a single Pilsner type malt.
I have derived this tentative formula from the linear regression of some (admittedly sparse) data points sourced from Narziss:
pH_Knockout ~= 1.86336 + (0.62686 * pH_Pre-Boil)
[wherein both variables represent room temperature measured pH’s]
I need to digest this a bit more. I always measure pre-pitch wort pH but never really worry too much about it. I usually end up in the sweet spot 5.1-5.2 range but the Amarillo IPA I made a couple days ago ended up around 5.5. Granted my mash pH was a bit high 5.7-5.8 at room temperature and I corrected it with some phosphoric acid.
I have now seen this twice in this recipe and plan to add a bit of acidulated malt to the next batch to bring the pH down in the mash tun a bit more. The calcium hydroxide and baking soda additions to the mash liquor are minimal so they should not have dragged the pH up very much. There is a lot of gypsum and epsom salts in my water profile but not enough to stabilize the pH at 5.48 like Bru’nWater predicts. BTW, this is my own designed water profile for a West Coast IPA. Also to note, the beer tastes pretty damn good with this pre-pitch wort pH.
A careful read of the BYO “retraction” as linked above by @dmtaylor indicates that it is an affirmation and not a retraction:
Mmm, that was excellent. I ate that article like I haven’t eaten in a week! :D A number of things that were bouncing around in my delightful coconut were put to rest in that article so I thank Silver_Is_Money very much for linking to it. One thing that hit me right in the head was the part where Palmer mentions that the correct pH for mashing and boiling MAY NOT be the correct pH for beer flavor and this is one of the things I am focusing on now: Mashing and boiling in the mid-5s (room temp) and then adding an acid addition to the kettle with 10 minutes left to 1) help the whirfloc do its job and 2) create a more pleasant-tasting beer by lowering the pH. A few beers I have on tap right now tell me this approach has merit. Better clarity and a nice, refreshing SNAP from the lowered pH.
I still have some questions regarding clarity and boiling at a lower pH but some here have already responded that they may be boiling at a pH of 5.2 to 5.3 (room temp pH) and do not experience clarity issues so that might be able to be put to rest too.
I’m slogging through that long HBT tread.
Some good stuff there, amongst the chaff.
Man, this is blowing my mind. For those of us who don’t have pH meters, let’s say you mash at a room temp mash pH of 5.5, which is in the 5.25 pH range at mash temp, which for something like a pilsner would be perfect. How much acid would theoretically be needed to drop the pH down to a good range for post boil pH? I’m using 88% lactic acid. I used to use 1mL near the end of the boil. Should I increase that to 2mL?
It depends upon the grist’s weight, the grist’s aggregate BC (buffering capacity expressed in units of mEq/KG_pH), the grist’s aggregate DIpH (pH when mashed within deionized or distilled water), and the actual (as opposed to targeted) room temperature pH one reads pre-boil. Much of this is being actively and ongoingly feted out and discussed here:
So I’m wondering if mashing higher, there would need to be a, say, 1mL lactic acid addition at the beginning of the boil, then another one just before the end of the boil. Because sparging is going to raise the pH of the wort in the kettle overall. I batch sparge and do not acidify the sparge water.
IME, acid additions towards the end of the boil seem to have a very small impact. I once measured my mid-boil pH and it was something like 5.47 and then I added 1ml of 88% lactic acid and when I took the pH as the wort was headed into the fermenter, it was 5.45 and both samples were measured at room temp. I’m trying to keep my mind from being blown so please don’t say this is blowing your mind. :P 
Well, hmmpf…I kind of just want to put a bag over my head and keep doing what I’m doing… But if this could mean even better beer, well, has to be worth exploring I’d think. My main worry now, is if I’m mashing at a higher pH and by your observations the pH isn’t changing much during the boil, I’m worried about my post boil pH being too high. Is that confusing enough?
Believe me brother, I am a by-the-numbers brewer and when some of these guys start talking fancy I have the bag in my hand ready to put it over my head, LOL. My latest gig is to just simplify things: Get my strike water to a pH of 5.5 prior to heating it and then mash away. I take the pH of the mash and find myself squarely in the ranges mentioned throughout this thread. My sparge goes the same way and I boil at that pH and then add 1 to 1.5ml of lactic acid about 10 minutes from the end of the boil. The results so far are encouraging and I feel a bit more comfortable simplifying things. Now where is that bag…
The most interesting part of that thread to me is Bryan’s screenshots of the offset between the pH as measured at mash temperature and room temperature. It appears to vary quite a bit rather than being some constant (like the often cited .25 or .35).
1 mL of 88% lactic acid will move a pH by 11.141 mEq’s.
(5.47 - 5.1) = mEq’s/(~35 x ~5) [for a 5 Kg. grist with a BC of 35]
0.37 = mEq’s/175
mEq’s = 64.75
64.75 mEq’s ÷ 11.141 mEq’s/mL (for 88% Lactic Acid at pH 5.1) = 5.8 mL
You likely needed to add 5.8 mL by which to move your grist to pH 5.1. In that case it is easy to see that 1 mL would not be seen as much of a change.
In fact:
(5.47 - X) = 11.141/175
X = 5.41 pH predicted after an addition of 1 mL of 88% lactic acid (for the case of my presumptions)
Sounds like a good plan and simplifying is always on my list of things to do. I may do this, aiming for room temp pH of around 5.5-5.6 and just up the amount of acid I add at the end of the boil from 1mL to 2mL (or maybe even 3mL based on Silver_Is_Money’s comment above). It isn’t that big of a departure from what I’m already doing.
Since Bryan mashes at relatively low pH’s to begin with, and (per Narziss data) the higher ones pH entering the boil, the greater the drop, one would not expect Bryan to observe much pH drop across the boil. Those observing 0.3 to o.35 pH points of pH drop across the boil are the ones mashing at room temperature 5.5 to 5.8 pH. Yet more evidence that mash pH in the days of yore was targeting what would be 5.5 to 5.8 if measured at room temperature.