Understanding Where I Missed My Numbers

[Eucrid]

A couple of weeks ago I did my first AG brew and I was mostly pleased with how it all went. I used this recipe here for the Russian River Row 2 Hill 56 clone. I plugged everything into Beersmith and I go my numbers back along with the brew steps that I tried to follow pretty closely.

My numbers came back reasonably close to the BM targets except for the FG

Est Pre boil gravity: 1.047
Measured PB Gravity: 1.049

Est OG: 1.055
Meas OG: 1.054

Est FG: 1.012
Meas FG: 1.008

So I'm wondering what would cause the FG to be that much lower? I fermented with US-05 at a pretty consistent 65F for the first week and a half and then I let it move back up towards 68/69F for a week after that.

Being my first all grain I did sort of mess up hitting my mash temp properly. I'm guessing thats the main reason for the lower FG, lower mash temp = more fermentable wort. Am I right in that assumption? Also does this not effect the Pre boil and original gravities?

 

[Yooper]

Being my first all grain I did sort of mess up hitting my mash temp properly. I'm guessing thats the main reason for the lower FG, lower mash temp = more fermentable wort. Am I right in that assumption? Also does this not effect the Pre boil and original gravities?

Yes, mash temperature affects the final gravity, but not the OG as it's the same amount of sugars in the wort- it's just that those sugars are a bit more fermentable so it will finish a bit lower. It's only a difference of .004- not much.

 

[NathPowe]

What did you mash at? If it was lower than what you entered into Beersmith that would certainly account for your measured FG going lower than the software's prediction. Also, it's not surprising to me that 05 took you a bit lower than what Beersmith predicted. I've had that happen to me several times on low-ish gravity beers like this one. That yeast is a strong attenuator given proper conditions. In any case, you could just try mashing a bit higher next time.

Regarding the discrepancies between your pre-boil gravity and OG - since your measured pre-boil was higher than the estimated, but your OG was lower than estimated I would look at your boil off rate in Beersmith - it's probably just set a bit too high. I had the same issue when I first started dialing in my system. Over the course of several brews I kept reducing the boil-off rate in Beersmith until my predicted numbers became more consistent with what my system was producing. For me, that's pretty critical across the board when using brewing software. Tailor the software to the system that you like to brew on. I think it's easier to do that than tailor your system to the software.

Just my two cents. Cheers.

 

[Eucrid]

Good advise on the boil off rate, thanks. I really do need to dial in my numbers better, I suppose it takes a few brews to get them spot on. First go was mostly me just trying to make sure I didn't make any massive mistakes. And I suppose I didn't, numbers weren't too far off. Got a life time to perfect this

As for the mash because I was a bit flustered with it all I didn't measure the mash temp properly but it definitely came in a bit low, maybe as low as 147/148. I recognised the error at the time and I've brewed twice since and hit my mash temp a lot more closely or spot on.

I'll keep an eye on US-05 too, my last brew was a blonde ale and I used it on that but I know my mash temp was bang on with that one so if it comes in low again I'll definitely have to aim a little higher than BS is telling me in future.

 

[Wolfbrau]

FWIW, I prefer higher attenuation in American styles. The drier the better. If the malt's not coming through, that's a recipe issue.

 

[smizak]

Regarding the post-boil number issue, I typically always aim to over-boil and come under the post-boil volume. If the gravity is too high, I use the dilution tool or a calculator to add the appropriate amount of distilled water and hit my target gravity dead on. Foolproof.