What's the worst that could happen? (pH question)

I've brewed a bunch of all-grain batches and have never given a thought to my ph. My efficiency isn't great, but conversion always happens and my beer is tasty.

Moral of the story: RDWHAH

 

Not much data to go on, but probably about the worst thing that could happen in this case is a low mash pH, outside the optimum range for Amylase (particularly Alpha Amylase) enzymes which convert your starches to sugars. So efficiency and/or wort sugar profile could be affected.

However, you had success with a Dark Mild. Depending on how dark the mild was (and what mix of grains you used to achieve the color), your Milk Stout might also be in an acceptable range. (Crystal malts contribute more acidity (per unit of color) than roasted malts.)

If you have (or can get) pH test strips, you might want to mash your milk stout grist with no modifications, check the pH, and if unacceptably low, add a little baking soda or pickling lime. Or you could cold steep your dark grains (apart from the mash). Or just not worry about it, mash with no modifications, and see what happens.

 

What can happen?

Poor efficiency.

Flavor not malty and rounded as you want as the low pH will make it sharp/tart or even acrid tasting.

 

Since you say the grains are crushed already, I assume they are probably mixed together. If not, you can consider steeping the dark grain separately.

Using bottled water, the calcium levels are likely to be low. You can bring them into the acceptable range with some basic water additions. I would add one half teaspoon gypsum and one half teaspoon calcium chloride to the mash for the bitter, and (more importantly) two teaspoons calcium chloride to the mash for the stout. Most LHBS carry these, if not you can easily order online and have it by the weekend. Cheers!

 

Assuming we know how much calcium is in the spring water (though we don't), why would you add more (total) calcium for the stout than for the bitter?

 

Because the stout has more dark grains, and Calcium will buffer the acidity. I don't think this is controversial.

 

Calcium in a mash actually decreases pH, because it reacts with phosphates from the grains, releasing protons (H+).

It's the phenomenon underlying Kolbach's observations about residual alklinity.

 

Ah, Kolbach.

 

More calcium will drop the pH unless there are sufficient Bicarbonate to buffer the Ca and acidity from the grains. Vikeman has this right.

 

Well first, we don't even know that there is a problem. But yes, if you steep your dark grains apart from the mash, they won't contribute to the mash pH. That's the difference.

 

When malts are kilned and roasted, the melanoidins developed make them acidic. That varies with the grain. You can do a search on cold steeping and see what you find. Just soak the grains overnight and add to the mash when ready to sparge out.

 

The water chemistry (which you don't know and adjust, yet) and the temperature can lead to the acrid flavors. Cold steeping avoids that with the lower temps.

 

With cold steeping, you might want to increase the amount of grain, since extraction won't be as efficient.

Serious astringency (due to grain tannins) requires both high pH and high temps. That's why cold steeping avoids tannin extraction. In your case though, you wouldn't be cold steeping to avoid tannins...you'd be doing it to have a less acidic mash pH.

If you do a regular (hot) steep, you wouldn't be doing anything special to avoid tannins, but you probably would not be extracting significant tannins anyway, because the pH in your steep would probably not be very high.

 

Another option is to mash your base malt until converted and then stir in your crystal and dark malts and let it rest for 15 mins. Vorlauf and sparge as normal. This will pull the sugars, color, flavors from the character grains and avoid the extra time/work of steeping the grains separately.