Second AG brew - Island 17 porter

[MrSpiffy]

I finally got a chance to brew again this past weekend, and decided to give the Island 17 Blackstrap Molasses Porter a try. As with my first, I brewed BIAB-style, and used just a little extra grain in case I didn't get good efficiency. So, I used 9.5lbs of 2-row, instead of 9lbs. I also accidentally grabbed roasted barley, instead of flaked barley, so I'm curious if someone knows how that might affect my brew.

The brewing portion went pretty smoothly. I mashed around 159°F for about 75 minutes, then drained the bag, did a quick dunk-sparge with 170°F water, and squeezed the last of the liquid out of the grain bag to get a pre-boil volume at just about 7 gallons. Perfect! But the cool-down was a huge pain. I didn't think things through very well, and had to float bags of ice and cold water in the kettle to chill the wort. I seriously need a wort chiller... It took a few hours to chill down to just over 80°F. I pitched right around midnight. The wort was nearly black.

While I likely didn't get a good cold break, the yeast took off pretty easily. It was bubbling away within hours. And with a beer this dark, I don't really care about clarity.

My pre-boil OG @ 7 gallons was 1.052 @ 76.5°F (1.055 corrected). Post-boil OG @ about 5.15 gallons was nearly 1.070 (corrected) with the molasses. I'm estimating a final gravity of ???

How many points will the 10oz of molasses add to my OG? I'm guessing it's around 0.003-0.005 higher with the molasses.

I think I did a little better than my first BIAB brew. If my numbers are correct, that should put me in the neighborhood of 89% efficiency. Using Palmer's calculations and PPG, I can get a maximum point value of right around 62 points, or 1.062 OG with 7 gallons. I got 1.055. That's crazy! I never thought I'd achieve that with BIAB. Is this correct? Or did I screw up some numbers here? Other online calculators are putting me more around the 75% range. So, I'm confused. (Although, that would make more sense to me.)

Another fun thing is that I found out my instant-read thermometer is slightly low, compared to my probe that I used to monitor mash temps, which appeared right on at 212°F when boiling. This instant-read only read 207.5°F at boiling. So, for all I know, my gravity numbers are even slightly low, since gravity goes down as temp goes up.

Just for the math, here are my numbers. I used Palmer's table of PPG numbers for most of these grains.

 

[MrSpiffy]

Well, this is going to get interesting... Apparently, I was supposed to use 10oz of molasses by weight, not by fluid ounces. So, I probably added around 15+oz of molasses. Hope this brew is drinkable...

 

[BrewinHooligan]

The roasted barley will give your porter a nice toasty flavor and I think it should turn out well in that respect. 159 is an awful high mash temp so there will probably be quite a bit of unfermentable sugars in there and your FG will probably be on the high side, but the extra molasses may counter that well by drying the beer out some. Give it some time after packaging for the flavors to meld and I bet you will enjoy this one. I tend to trust the online efficiency calculators personally, I don't trust myself to calculate efficiency by hand.

 

[MrSpiffy]

Well, I followed the proper calculations, and measured the OG before the boil with no molasses added. Maybe my water volume calculations were off, but not by too much. I guess I'm curious if I messed up my numbers somehow. If not, then my efficiency is correct. But why is it so different than the web site calculations out there?

Strangely enough, the Brewer's Friend calculator puts me around 88%, which is close to what I calculated.

 

[BrewinHooligan]

My only guess is that the PPG that Palmer gives varies from what online calculators are using.

 

[MrSpiffy]

I've noticed that many calculators only show post-boil gravity values at 5 gallons, not pre-boil gravities. Perhaps that's what's throwing the whole thing off. The Brewer's Friend calculator can be used for either.

And by the way, I realize the mash temp was a bit on the high side, but I was shooting for the 158°F mash temp in the recipe. It will have lower alcohol content and more body. I'm good with that. I like thick, heavy beer. So, no big deal there. And like you said, it's possible the molasses will balance that out with extra sugars to ferment.

EDIT: I just checked another calculator at BrewHeads.com, and they're putting pre-boil efficiency in the 88% range. So, I guess my numbers are correct. Never thought I'd get nearly 90% extraction, especially with BIAB. Very cool!

 

[MrSpiffy]

I finally got around to bottling this batch. The FG sample tasted pretty good, a bit sweet (from the priming sugar), had some roasted notes, coffee, and chocolate. Maybe a bit of stone fruit, like dates, or even raisins. It has that tawny port color to it, where it's really, really dark, but has that rusty brown color to it when you can see it. Trying to see through it is futile. Even in the hydrometer tube, you couldn't see any light through it.

FG was 1.028 (with priming sugar, so minus 0.002 for that) @ 69°F. Corrected, that brings it to 1.027 @ 60°F, after taking two points off for the priming sugar.

So, if OG was narly 1.070 and FG is at 1.027, it looks like ABV is approximately 5.64%. That seems pretty low, to me. However, I have to remember that the mash temp was on the high side, and probably produced a significantly less-fermentable wort, yet a beer that has a thicker, heavier body and mouthfeel with more sweetness. I think if I make this beer again (we'll see how it tastes once it carbs up), I'll use a lower mash temp to get a higher ABV. But we'll see how it turns out after a few weeks.