When it comes to making dark beers, one important consideration is how to go about using the roasted grains. Based off of a recommendation from Gordon Strong in Brewing Better Beer, I began adding roasted grains during the last 10 minutes of the mash, a technique referred to as capping the mash, believing it would lend a smoother roast character. After years of using this method, I finally did a proper xBmt, comparing it to the same beer with the roasted malts mashed the entire time. Results are in!
Awesome! And I am not surprised
Easier sounds good to me, I will continue to mash all together as I have been doing with “proper” water treatment. Great exbeeriment Marshall
Thanks, Marshall. It’s pretty interesting. I mash it all together and honestly expected the opposite, only because of the lower pH - I love the more rounded roast at 5.5 -5.6 pH for a dark beer. Regardless, this does nothing to make me want to stop mashing it all together.
I had just asked about his in another post. I’m going to look into this when I can read it fully.
I’ve always suspected that capping the mash simply results in less extraction of colour and flavour from roasted malt and this seems to support that idea. Astringency from tannins comes from high mash pH, oversparging or high sparge pH, so perhaps people who get lower astringency from a capped mash are not treating water properly for the main mash.
Fascinating results, especially the part about pH being only hundredths of a point different. I shall henceforth return to full mashes for my stouts and porters, as depth of flavor and color are more important to me with these styles than the theoretical but probably non-existent “smoothness” from late capping.
I have zero constructive comments for this xBmt. Well done. Thank you again, Marshall.
Great data. I love not having to make my brew day more complicated. One question, though… did you check OG for each batch? I have never understood why having denatured enzymes in a dark malt matters. We are, after all, interested in using the enzymes from our base malts to provide the sugars for conversion. If there are starches that could be converted in the dark malts, we are sacrificing some yield if we don’t do a full mash.
Nice experiment - final pH being similar makes sense since the roasted barley still had time to acidify the wort for 10m at the end. Wonder if the fairly different mash pH’s made a difference?
It’s interesting that the difference in the mash for 1lb of roasted barley was that big. Brun Water and Kai’s water calculator both predict only a 0.1 drop from roasted barley with this recipe, as Kai’s original findings shows that roasted actually contributes less acidity that crystal, per each *L of SRM. Perhaps it varies by brand and type of roasted malt.
Might have something to do with it being Simpsons which I use. Simpson’s RB is ~650L, whereas Briess for example, is only 300. Simpson’s actually smells like espresso when you stick your nose into the bag, whereas most other brands I’ve tried are much more subtle.
Haha, like I said, I always look forward to your constructive comments 
As someone has pointed out in the comments section of the brulosophy website, the difference in proton concentration, [H+], for a pH of 5.0 vs 5.3 is 5 x 10-6 mol/L. The difference for 4.16 vs 4.19 is 4.5 x 10-6 mol/L for a difference of .5 umol/L. Sub-micromolar concentration differences might be beyond the precision of the instrument. If you need convincing the equation is:
pH = -log[H+]
so [H+] = 10-pH
Ya know, it seems like I keep saying it over and over in these recent Exbeeriments…but this is no surprise and something I’ve been saying for years. I even posted about it in a thread here recently. Sorry to be the “Told Ya So” curmudgeon, but what can I say?
Or rather, this should imply that the pH drop, buffering, etc that went on during fermentation was likely similar in both beers.
Oooohhh… that sounds nice. Perhaps for the next dry stout (we brew it all the time - pretty sure it’s the only thing we have a nitro tap for!) I’ll search out Simpsons and see what’s different.
For me, adding the dark grain late makes brewday less complicated - no water spreadsheets, no weighing salts, no varying acid additions, no pH meter, no tinkering. If you like doing those things, great! I don’t.
I use the same water and mash pH profile with minimal additions for every beer and get consistent results, regardless of the style I’m brewing. That, I believe, is Gordon’s larger point.
I get similar aromas from Thomas Fawcett Roast, if you can’t find Simpsons. I love it in my RIS.
Interesting results indeed. I’d like to think that I would have preferred the late addition stout, but who knows? I now intend to do a side-by-side and see for myself.
One thing I can’t get past is the color difference. It makes sense that less color translates to less roasted flavors, I’m just not experiencing that color difference when I employ this technique. I do seem to get quicker and better clarity however. Not sure why. But again, I’ll give the experiment a whirl for myself and decide.
Good stuff Marshall.
I spent several years doing late additions, cold steeping, etc. in an attempt to smooth out my dark beers. After several years, I realized they had become so smooth they were insipid. I went back the other way and now even use a small amount of black patent in dark beers to get the hit of flavor I’m looking for.