Multiple batches don't reach expected final gravity

Background: "New" brewer in 2011 (July) (after not having brewed for over 15+ years). Did a couple extract recipe's and then jumped to all-grain using a BIAB for mash and sparge. 13 batches since July.

Hey all -
I've run into a somewhat recent issue with my batches. I'm not sure quite when it started (need to go through my records in detail). For my last four or so batches, the expected final gravity level (e.g. 1.012) hasn't been reached. Instead, it seems to have stopped around 1.018 or so. Prior to this, the batches were pretty much spot on what was expected.

What is "expected" varies by what is being brewed. But this has occurred with S-04, S-05, and s-33, and with various styles (ESB, IPA, Wit, SMaSH). I've done fresh yeast and also re-using yeast from an older batch (that had been saved in a sterilized mason jar).

When it first occurred I thought it might be from too low a fermentation temperature as I ferment in an old refrigerator in the basement and my basement was getting into the low 60's/high 50's. So, I wired up a heat source and eventually wired up an e-bay digital temperature controller + the heat source (DIY paint bucket w/light). Then I did a batch with better low end temperature control where I made sure the temperature did not go below 64 degrees, and even ramped it up to 68-70 after the visible fermentation activity died down. Same result.

So, I'm looking for ideas as to what the issue might be. Things on my list (so far) are:
1. Incorrect (too high) mash temperature. Note: I do BIAB for my mash and batch sparge. Action: Verify thermometer accuracy and/or try lower temperature mash.
2.Can an incorrect sparge temperature affect FG?
3.Too little yeast @ pitch?
4.Not enough oxygen when yeast is pitched?
5.Fermentation temperature too low? (Already tried to solve.)
6.Hydrometer inaccurate. (I did try H20 @ 60 and it reads dead on at 1.000)
?
?

One other note. The resulting beers have tasted just fine, and have come out (after conditioning/cold crash) nice and clear. (Except for the wheat, which was left cloudy on purpose.) No bottle bombs, but I do keg and when I need bottles, take it from the keg. Also, one one batch I tried mixing up the yeast to re-suspend it and then letting it sit at 70 degrees for another week. When I took another reading, I think it was slightly lower (maybe .001 or .002), but that amount could simply be my old eyes reading error, or a slight temperature fluctuation.

Two other things:
1) I broke my hydrometer, but I can't remember when in terms of this problem.
2) I (sometime in the fall) decided to switch from doing batches on an electric stove to doing the boil via propane (outside). I did this as I was unable to get full boils indoor for 5 gal (final) batches. But I still do the mash step on the stove-top (BIAB) as before. I've moved the sparge step outside to the boil kettle as I heat the sparge water to 185 and then do the sparge and then add back in the mash results and then have everything in the actual kettle ready to boil.

Suggestions?
Thanks!

Maybe try a brand new stand of yeast, similar to what you were using

If I remember correctly, it doesn't matter if you put to little yeast in your fermenter as long as you put enough to start the fermentation process. The yeast multiplies a it attacks the sugars.

I'm guessing mash temperature. Be sure you are getting the thermometer way down into the center of the grain. I have noticed mash temp can vary a lot from where you place your thermometer. if you're just sticking it in the top couple of inches of grain, it's likely warmer in the middle by several degrees.
That said, your FGs aren't that far off, and I'm sure you have good beer. Just a little maltier than you might have expected.

gingerdawg said:

I'm guessing mash temperature. Be sure you are getting the thermometer way down into the center of the grain. I have noticed mash temp can vary a lot from where you place your thermometer. if you're just sticking it in the top couple of inches of grain, it's likely warmer in the middle by several degrees.
That said, your FGs aren't that far off, and I'm sure you have good beer. Just a little maltier than you might have expected.

Click to expand...

Yes, I thought of mash temperature. I'm wondering if doing BIAB I have more variability on it due to having the bag sit in a bag of water. I will try shooting for a somewhat lower temperature on my next batch.

Any other ideas out there? Can sparge temperature affect FG?

audihonda said:

If I remember correctly, it doesn't matter if you put to little yeast in your fermenter as long as you put enough to start the fermentation process. The yeast multiplies a it attacks the sugars.

Click to expand...

Underpitching will lead to beer, but it also stresses the yeast and leads to off flavors. It is generally bad practice, and is pretty easily avoided.

Stress on the yeast can cause them to peter out earlier than they should, and could be the cause of this problem.

OP: What possibilities on that list have you looked at/taken care of? I would guess pitch rate or oxygenation. Some more details regarding specific recipes and procedures would help, but those two seem the most likely to me, from what you have talked about so far. As stated, depending on mash temps and how well your thermometer is calibrated, unfermentables could also be the culprit.

You mention breaking your hydrometer along the way? When did this happen, and did you replace it?

Your thermometer would be the first suspect to me as I just went through that problem where my thermometer was reading 4 degrees high so I mashed at 148 instead of the 152 wanted and my FG was running 1.002 to 1.005 instead of the 1/014-1.016 that I expected. You can use the ice/water mix and the boiling water as reference points for calibration but if your thermometer isn't perfectly linear you could be off at mash temps.

Too high a mash temp is certainly one possibility.
You say you broke a hydrometer, but you calibrated the new one and it is accurate. Did you ever calibrate the old one?
Where are you getting your expected FG from, and how do you know the expected FG is estimated accurately?
Mashing for a longer period will also help reduce the FG.
An incorrect sparge temperature will not affect the FG.
Have you started brewing beers with a higher OG? These will have a higher FG as the attenuation is a constant percentage applied to the OG.
Assuming you are brewing 5g batches with a reasonable OG, and using a full packet of yeast, I doubt that underpitching would be the cause.

Hope this helps,

-a.

ajf said:

Too high a mash temp is certainly one possibility.
You say you broke a hydrometer, but you calibrated the new one and it is accurate. Did you ever calibrate the old one?
Where are you getting your expected FG from, and how do you know the expected FG is estimated accurately?
Mashing for a longer period will also help reduce the FG.
An incorrect sparge temperature will not affect the FG.
Have you started brewing beers with a higher OG? These will have a higher FG as the attenuation is a constant percentage applied to the OG.
Assuming you are brewing 5g batches with a reasonable OG, and using a full packet of yeast, I doubt that underpitching would be the cause.

Hope this helps,

-a.

Click to expand...

Answers:
I had never calibrated the old one. For the new one, because of this problem, I measured the SG with H20 (tap water from my well) @ 60 was right on 1.000 (as best as my eyes can tell).

My mashes have been 60 minutes (typically), sometimes a few minutes shorter/longer.

The beers have ranged. The last n batches have been:
1. Sierra Nevada Celebration clone:
BeerSmith 2 Recipe Printout - http://www.beersmith.com
Recipe: SN Celebration (Dean Larson Recipe - original scaled to 5 gallons
Brewer: JT
Asst Brewer:
Style: American IPA
TYPE: All Grain
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 5.96 gal
Post Boil Volume: 5.46 gal
Batch Size (fermenter): 5.00 gal
Bottling Volume: 5.00 gal
Estimated OG: 1.065 SG
Estimated Color: 10.0 SRM
Estimated IBU: 45.2 IBUs
Brewhouse Efficiency: 70.00 %
Est Mash Efficiency: 73.5 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
11 lbs Pale Malt (2 Row) US (2.0 SRM) Grain 1 84.6 %
1 lbs Caramel/Crystal Malt - 60L (60.0 SRM) Grain 2 7.7 %
1 lbs Carapils (Briess) (1.5 SRM) Grain 3 7.7 %
0.87 oz Chinook [13.00 %] - Boil 60.0 min Hop 4 37.9 IBUs
0.22 oz Chinook [13.00 %] - Boil 30.0 min Hop 5 7.3 IBUs
0.22 tsp Irish Moss (Boil 10.0 mins) Fining 6 -
0.87 oz Cascade [5.50 %] - Boil 0.0 min Hop 7 0.0 IBUs
1.0 pkg Safale American (DCL/Fermentis #US-05) Yeast 8 -
0.87 tsp Yeast Nutrient (Primary 3.0 days) Other 9 -
0.43 oz Cascade [5.50 %] - Dry Hop 7.0 Days Hop 10 0.0 IBUs
0.43 oz Centennial [10.00 %] - Dry Hop 7.0 Days Hop 11 0.0 IBUs


Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 13 lbs
----------------------------
Name Description Step Temperat Step Time
Mash In Add 17.33 qt of water at 162.9 F 152.0 F 60 min

Sparge: Batch sparge with 2 steps (0.21gal, 2.98gal) of 168.0 F water
Notes:
------


Created with BeerSmith 2 - http://www.beersmith.com
-------------------------------------------------------------------------------------
On this batch my measured post-boil SG was 1.070 and my measured FG was 1.018 vs. a beersmith estimated 1.013.

2. Blue Balls (Blue Moon Clone) FG was close to 1.020.
3. Vienna Smash FG was close to 1.020.
4. Captain Hooked on Bitters (Redhook ESB clone). FG was close to 1.020.

I don't believe I had this issue prior to these batches. None of these batches have a super high SG (the celebration clone was the highest).

All the estimated gravity levels are via beersmith.

I guess I need to stop guessing and start a) calibrating the equipment and b) try to make sure my mash temperature is actually what I think it is.


Edit: Used a package of s-05, not .9 package. Also, group buys rule...I was able to make this recipe for under $15, which includes the yeast that I will re-use at least a couple of generations.

djfriesen said:

OP: What possibilities on that list have you looked at/taken care of? I would guess pitch rate or oxygenation. Some more details regarding specific recipes and procedures would help, but those two seem the most likely to me, from what you have talked about so far. As stated, depending on mash temps and how well your thermometer is calibrated, unfermentables could also be the culprit.

You mention breaking your hydrometer along the way? When did this happen, and did you replace it?

Click to expand...

The only things I've done so far is:
a) Ensure fermentation doesn't stall by too low of a temperature by wiring up an e-bay controller to a old fridge with a DIY paint-can (w/light) heat source.
b) Measured the new hydrometer with well water @ 60 to verify that it shows 1.000 (it did).

The problem is that I can't remember exactly when I replaced the hydrometer...I was taking a FG reading and dropped it, so had to postpone the reading until the next morning when I was able to get another hydrometer. I don't *think* this is when the issue started. One thing I need to do is keep better notes!

Regarding oxygenation, my technique to date (both for the batches that worked and for the ones with the issue) has been to simply pour the wort from a bit of height into the fermentation bucket....is this enough, and if not could this result in symptoms like I am seeing? As I mentioned on a prior post, on the first or second batch this happened on, I tried stirring up the yeast, raising the fermentation chamber temperature to 69-70, and letting it sit another week).