I'm planning on making a heavy stout Friday and then using the grain and maybe some DME to make a nice little porter. I've made a handful of really decent stouts and always look at all that unused sugar. My problem is building the recipe. I don't know how to use the online calculators for OG/ FG when using used grain. Without that, I can't determine how much DME to be prepared to add as well as yeast cells needed. I guess in the end, where do I start? My original stout is going to use 28lbs of grain, 65% efficiency. Boil gravity of 1.106. How do I know what I can get out of the remaining grain? I'm hoping to get to around 1.060 for the Porter. I'd rather have an idea of what I'm dealing with prior to pouring in pounds of DME. Plus, that helps with the hops, yeast planning and estimated FG. Thanks for any help. Link to my stout recipe. http://www.brewersfriend.com/homebrew/recipe/view/377863/holzie-s-own-b2
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Adding DME is the easy part. How much you'll need to hit a certain target gravity depends on your processes - but it's simple to calculate once you know the starting gravity of your 'small wort'. You can measure that once it's in your kettle, and add DME as needed to get to the appropriate pre-boil gravity for a 1.060 wort. (e.g. 1.048 if you're boiling 6 gal down to 5) If your pre-boil volume is 6 gallons for the porter, each pound of DME will raise the gravity by about 7.5 points. If your extraction efficiency is 65% for the first batch, you probably can't do much better than 15% on the second batch. So you'd be looking at ~ 6 gallons of pre-boil wort @ 1.026. To get that where it needs to be so you end up with 5 gallons @ 1.060 post-boil, you'd have to add approx. 3 lb of DME. Keep in mind, this is all very 'ballpark' with a few assumptions made about your sparge technique, batch sizes, boil-off rate, etc - and the biggest wildcard will be how much of the available sugars you actually remove from the tun for the first batch.
That's awesome, thanks. I took several years of calculus and I'm pretty good with numbers, but I'm not sure I followed all of that. At any rate, I believe I'll be able to get around 1.035 with the "2nd runnings". Looks like I'll need around 5 lbs of DME. That should do it.
So, looking at prior stout batches, one of our previous came out too sweet. The OG was 1.102 and FG 1.040. According to my number/ recipe that is where this one will stop. Isn't the FG directly related with how much residual sugar remains, meaning sweetness? Is there a method that gets this lower? Do you pitch a 2nd yeast? From my research, the yeast attenuation will only get you so far, so that helps determine FG. What if I want to get it down another 20 points? It's not like there are many yeast that can handle 85% attenuation and 12% ABV. Any insight? Pitch another yeast after day 4? Right now I'm using Omega Yeast Irish Ale 005, I think.
I've used this table twice. I've been within a point both times on my batch sparge system: https://www.morebeer.com/brewingtechniques/library/backissues/issue2.2/moshertable.html
A final gravity of 1.040 for a wort that started at 1.102 is only ~ 59% apparent attenuation. Taking it down to 1.020 puts you at 79% aa and 11% abv. 79% isn't an unreasonable number - and you *might* even be able to get close to that with an irish stout strain if you pitch A LOT into well-oxygenated wort - provided you kept your mash temp low enough to maximize the fermentability of your wort. Something like WLP001 would have been a better choice though, imo. 11% abv is no problem for it, and it attenuates better than typical irish strains. I'm not a big fan of pitching multiple strains (unless it's a blend used from the start)... but I'm sure plenty will argue in favor of it. I'd prefer to figure out why your attenuation was so low in the first place and address that instead. Probably some combination of your mash temp, pitching rate, and O2 levels. You need a big-ass starter for a high gravity wort like that, and it won't matter much how many different strains you throw at it if you've got a highly dextrinous wort and low cell count.
Thanks a ton for the info. That was only my 2nd attempt at a big stout and a different person was manning the yeast controls. Since then, I've learned a ton about yeast and pitch rates. We were pretty sure that we pitched a low number, but now I'm more convinced. As for this one, I'm certain that I pitched the right number with a great starter. I just hope that I shook the hell out of it enough to get good oxygen. I should have remember to borrow my friends oxygen. I made a quick decision on the Omega Irish to help with starter number 150/ pack instead of 100. Plus, I liked that the Iris yeast could handle up to 13%. I'm keeping the temp down to 64 or so during fermentation also. I'll raise it to 70 for a few days, transfer to secondary and throw oak and vanilla in.
