BIAB Troubleshooting Repeatedly Missing FG

[Steven_C]

Hi All,

I've been a lurker for a long while, but it's time for a post. I recently converted from extract brewing to BIAB. I've done four batches so far (fourth is sitting in the fermentor), and they have each suffered the same fate. I have hit OG each time, or close to it, but I end up only getting about 75% of the way to the desired FG. Some examples:

• Irish Red Ale: OG of 1.049 (1.052 was target), but FG was only 1.026 (1.013 was target)
• Porter: Hit intended OG of 1.050, but FG was only 1.023 (1.012 was target).
  
• Imperial Stout (currently in fermentor): OG of 1.098 (1.105 was target), FG has been sitting at 1.053 (1.030 is target) for about 8 days.

All of these used Safale S-04 dry yeast. I get good fermentation (the Imperial blew the lid off the Big Mouth Bubbler, even with a gallon of head space) starting about 12-18 hours after pitching like I should. I even sprung for the oxygen kit on the last two to make sure that wasn't the issue.

I mill my own grains and crush to the smallest setting. I know that's something that can help efficiency.

If I had to guess, I would bet I'm not getting good conversion and have a higher percentage of non-fermentables than I should. I'm not sure how I can test that though. I should also say, I haven't been using BIAB recipes, but have been using traditional all-grain recipes without any alterations. Is that my problem?

Hoping someone here can lend some advice to a newbie.

Thanks.

 

[tripeland]

BIAB is all-grain. There is no need to alter recipes except for adjusting for batch size and your expected efficiency. None of that really matters for FG though. Since you are close to hitting your OG then all the scaling is likely good.

Two things to consider:
1. How are you measuring FG? Hydrometer or refractometer? Refractometer will give false FG reading.
2. What temperature are you mashing the grain? A high mash temp will increase the amount of unfermentables and raise FG.

All things aside, how does the beer taste? Does it taste sweet?

 

[Jtvann]

I'd wonder about the thermometer calibration. Mash temps seem to be off on the high side by quite a bit.

How long do you mash for? It's pretty easy to get full extraction pretty quick, but a long mash tends to more fermentable wort.

I'd this were my problem, I'd either mash 5 degrees lower, or 30 mins longer ... or both.

 

[Steven_C]

BIAB is all-grain. There is no need to alter recipes except for adjusting for batch size and your expected efficiency. None of that really matters for FG though. Since you are close to hitting your OG then all the scaling is likely good.

Two things to consider:
1. How are you measuring FG? Hydrometer or refractometer? Refractometer will give false FG reading.
2. What temperature are you mashing the grain? A high mash temp will increase the amount of unfermentables and raise FG.

All things aside, how does the beer taste? Does it taste sweet?

I've been using a refractometer. I didn't know that about giving false FG readings. So I could not really have a problem?
I've been mashing at 153 (strike at 161 before grain is added).

I just tasted the beer in the fermentor, and actually, it doesn't taste very sweet. I think you might be right about the refractometer.

 

[Steven_C]

As an update, just found a adjustment calculator for my refractometer, and I'm basically right where I should be! Thanks @tripeland