Consistently low FG’s

[Tony B]

I’ve only brewed 8 batches of beer. The first 2 with extract and the rest have been BIAB. The extract batches hit pretty close to expected FG. All of my BIAB batches have been lower than expected. They have all finished at about 1.007 when I’ve expected 1.010-1.012. The beers taste ok. They don’t seem dry. I have tried different mash temps and used different thermometers to rule that out. I’ve mashed from about 150F-155F on various batches.
A bit about my process…
I mash in the kettle, on the stovetop and have tried a sous vide stick and keeping the burners on low to hold at desired temperature. I do stir quite a bit to try to equalize the temp.
I also mash with 5 gallons water and after draining and then removing the bag I add boiling water to get up to pre-boil volume.
Just looking for any suggestions on where to start ruling out other variables or how to alter my process. I am using the current method because I live in a condo and don’t have a lot of space.

 

[day_trippr]

Just for the record, when you are hitting your pre-boil volume, are you also hitting your expected pre-boil gravity? Or - skipping ahead - is your volume to the fermentor and its "Original Gravity" per recipe?

Cheers!

 

[Tony B]

Just for the record, when you are hitting your pre-boil volume, are you also hitting your expected pre-boil gravity? Or - skipping ahead - is your volume to the fermentor and its "Original Gravity" per recipe?

Cheers!

I have not been checking preboil gravity but have consistently been hitting within a couple points of expected OG. I generally cool my wort and rack to FV, then take a sample from the spout on the FV prior to pitching yeast.

 

[dmtaylor]

What yeast have you been using? US-05 by any chance? Yeast selection matters.

 

[Dland]

If the beer tastes good, perhaps you don't have a problem.

If it is not the yeast, it is likely somewhere in mashing process.

As suggested in second post, check pre boil gravity and gravity of wort before adding back water. Perhaps the grain is absorbing more water than recipe calculated.

You might also want to check your hydrometer, even though it seemed OK with the extract batches. Good to have a spare anyway.

 

[Tony B]

What yeast have you been using? US-05 by any chance? Yeast selection matters.

I have used several strains. WLP 001, WLP 029, Omega lutra and imperial global. Both liquid, dry with and without a starter.

 

[JakeBowden]

Lutra is known for high attenuation and thus fermenting to low FGs. Also, check your mashing temperature. Beta Amylase, active between 140F-150F, will promote a lower FG. If you are consistent with those low FGs, then you could boost your mash temperature to use alpha amylase, which will promote a higher FG. Also, it's important to make sure your thermometer is properly calibrated. If you think you are mashing at 152F but the real temperature is 148F, then you will be using only beta amylase, and thus your final gravity will drop.

 

[VikeMan]

All of my BIAB batches have been lower than expected. They have all finished at about 1.007 when I’ve expected 1.010-1.012.

Where did the expectations of 1.010-1.012 come from?

 

[Tony B]

Lutra is known for high attenuation and thus fermenting to low FGs. Also, check your mashing temperature. Beta Amylase, active between 140F-150F, will promote a lower FG. If you are consistent with those low FGs, then you could boost your mash temperature to use alpha amylase, which will promote a higher FG. Also, it's important to make sure your thermometer is properly calibrated. If you think you are mashing at 152F but the real temperature is 148F, then you will be using only beta amylase, and thus your final gravity will drop.

Yep. I’m trying to rule things out that could be misleading. I’m using three different thermometers and for. Batch I brewed yesterday I used a different hydrometer. I hit my OG dead on, so we’ll see how it finishes. Using WLP-521 Hornindal for this one. Expected FG is 1.009.

 

[Tony B]

Where did the expectations of 1.010-1.012 come from?

I build me recipes on Brewers Friend. Not sure to what degree their software accounts for mash temp, but I was able to hold a batch yesterday between 153F and 156F. I was shooting for 154.

 

[VikeMan]

I build me recipes on Brewers Friend. Not sure to what degree their software accounts for mash temp, but I was able to hold a batch yesterday between 153F and 156F. I was shooting for 154.

The reason I asked is that most software doesn't consider the makeup of the grain bill when predicting attenuation %. I think Brewer's Friend is supposed to, but I'm not sure how well. I just built some quick (mostly default values, a random yeast strain, and varying only in grain bill) recipes with 100% German Pilsner, 100% American Black Malt, and 100% American Crystal 80. Here's what it predicted for apparent attenuation with each of these grain bills.

German Pilsner: 73.1%
American Crystal 80: 73.3%
American Black Malt: 73.7%

Not only should there be bigger differences, but the differences are actually going in the wrong direction. Note: I only checked these three.

 

[dmtaylor]

@JakeBowden is onto something regarding calibration. I would check calibration of your hydrometer in plain room temp water to ensure it reads 1.000. Mine often does not, reading a couple points higher or lower. This can obviously affect both the OG and FG readings. Then also check your mash thermometer in both ice water and boiling water adjusted for your elevation. Again, thermometers are often off by as much as 3 or 4 degrees, so if you are mashing cooler than you think, it will increase attenuation.