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Water for a stout

Without knowing anything about my well water, I made Beersmith’s dry irish stout a few months ago and hoped for the best. 5# maris otter, 2# flaked barley, 1# roast barley, and 10g gypsum. It came out fantastic and now I’m looking at making a larger batch of it.

Fast forward to today, and now that I have my water report and have a little practice with Brun Water, I enter the recipe as brewed and it’s a little surprising that it came out as good as it did. It appears that the recipe achieves an acceptable mash pH by using a massive dose of gypsum, but some of the minerals are off the chart.

It looks like I can get really close to the “Black Malty” or even the “Dublin (boiled)” profile with modest amounts of gypsum, calcium chloride, sodium chloride, and phosphoric acid. However, I can’t argue with the results of the first method, it really is fantastic.

How would you guys approach a stout? I’m tempted to try the new water profile to make the direct comparison, but the whole reason I want to rebrew it is so I have more of it.

Dark roasted grains reduce the mash pH big time, so if you have moderately hard water, you don’t need to add any salts, or if you add anything, it might be a tiny amount of baking soda to INCREASE mash pH and keep it from being too LOW. This is contrary to all other styles when it can be difficult to get the mash pH low enough.

Alternatively, a lot of people these days are saving their dark roasted grains to add towards the end of the mash. This allows the usual salt additions for mash pH control and flavor purposes, and also minimizes acrid, tart, astringent flavors from the dark grains and can result in a smoother tasting stout.

Personally, I would use my raw water, skip the salt additions, mash with all the grains in, and be done with it. If anything, like I said, I might have to add like a half teaspoon of baking soda, and this might even need to occur after the mash is finished and be added to the boil kettle, depending on the exact pH.

Desired mash pH in any case is about 5.1 to 5.5, with 5.3 being optimal.

Play with salts all you want. It’s one of the least utilized areas in homebrewing. A lot of classic beers get a great deal of their flavor from their water source. It is entirely possible that you have found a water and salt profile that tastes great. If so, more power to you! That being said, it might be worthwhile trying the Bru’n Water method to get the water dialed in “the right way” for a side-by-side taste comparison. Then taste them blind. That’s the only way to know for sure which one tastes better.

Thanks Dave, I’m trying to use the spreadsheet as a learning tool - if I change one thing, how does mash pH change, etc. I entered the recipe with my well water without the gypsum, and get a pH too high, but the large amount of gypsum brings it down to where it should be (about 5.6). I guess there’s nothing gained by recreating the recipe exactly, other than more really good beer.

Wow, your water must be super alkaline / high bicarbonates. If that’s the case then I can see why you need to acidify. You might even want to try phosphoric acid additions or acidulated malt or something like that to get your pH down to 5.3.

Sometimes Martin Brungard hangs out around here, and especially on the AHA forum. You might want to repost your question there in the hopes that he’ll see it and respond, as he’s far more an expert than most other “regular” folks like me.

High bicarbonates… It’s great drinking water, but apparently not ideal for brewing. I used phosphoric acid last weekend for the sparge water, and boiling/decanting the mash water prior to using it to knock down the calcium and bicarbonate. It was actually really interesting seeing the change in the water, you definitely get used to seeing the “bubbles” coming out of the heating water to tell that it’s getting hot.

I’m glad it worked out for the stout. A modest level of alkalinity is good for most stouts and porters, but to get the crisp acidic flavor produced by a Guinness, you need to start with almost RO quality water and reserve the roast barley addition until the end of the mash. I’m still betting that your stout was very tasty since roast flavors tend to become rounder and fuller with a higher pH. Sure, its not a knock-off of Guinness, but still good.

The preboiling technique should be useful for other styles, especially paler beers. It’s just a PITA and an energy waster, but it works. Be sure to read the information on Decarbonation by Boiling in the Water Knowledge page of the Bru’n Water site. It should help you to estimate what the post-boiled water quality might be at and that should help you to plan other water additions.


Thanks again for your help, Martin! I went through the Water Knowledge section, and figure I can get the calcium down to 12 and the bicarbonate down to 98 through your equations. It’s not too bad boiling the water the day before brewing, and it certainly uses less gas than driving to the store for water. Not something I want to do all the time, but I think I’ll try it with my next IPA.

I guess my question boils down to (heh) whether it would make a better stout to correct pH and mineral levels with phosphoric acid and modest amounts of salts, or whether correcting pH through a large dose of gypsum would be “good enough.” I think I know the answer, but wanted to get some opinions.


I find that keeping the sulfate level relatively low is a good thing in roasty beers. Sulfate’s effect is rather drying on the palate and so is roast flavor. Therefore, I find that the flavor and perception can be reduced by adding a bunch of gypsum. Keeping the sulfate below 100 ppm seems to work for me. Trying to achieve an appropriate mash pH via large calcium salt additions has not proven to be a good way to produce good tasting beer.

All things in moderation!

Well for the sake of science, I’ll brew it next time with a more “balanced” mineral profile and compare the two side-by-side. Should be interesting!

Just an update - I bottled this a few days ago. I kept the roast barley out of the mash until the last 10 minutes, and adjusted the water to pH 5.4 using phosphoric acid with just the MO and flaked barley. Even flat, it’s fantastic! Smooth and crisp, and without the burnt flavors in a lot of stouts. Trying it side-by-side with the other recipe, it really points out the flaws in the other approach.

Thanks again!

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