Can't seem to hit FG

[Rockindaddy]

I'm on about my 5th BIAB batch and no matter what, I cannot get my FG to where I want it to be. I have two batches fermenting right now and after 3 weeks the FG is stuck at 1.026 on BM's SWSBO Slayer recipe (started at 1.051) and a batch of Centennial Blonde stuck at 1.024 (started at 1.046). I did yeast starters on both batches and they "looked" like they were fermenting fine. One (SWSBO) is in a bucket and there is about a 2" ring of dried krausen around the top and it also had a good amount of airlock activity for the first few days. The other (Centennial) is in a glass carboy and only has about 1/2" ring around the top. I don't think they are going any lower. Any ideas of what I might be doing wrong?

 

[FastAndy]

How are you checking your gravity? Hydrometer or refractometer? Any temp swings during fermentation? are you aerating before pitching? With a krausen ring like that it sounds like the yeast were doing their job. How long have these been fermenting?

Cheers

 

[Rockindaddy]

Checking with a hydrometer. Both have been fermenting for 3 weeks. The bucket is in my freezer fermenting chamber at 68 degrees and the carboy is in my closet in a bucket of water with wet towels on it and fluctuates between 68 and 72 degrees. In the bucket I stir the crap out of it with my stir stick and in the carboy I shake hard for a few minutes.

 

[FastAndy]

Hmm, sounds like there isn't anything in your process that would cause a stuck fermentation. What are the expected FG's supposed to be? Make sure to correct for temp when using a hydrometer.

 

[Rockindaddy]

Centennial Blonde should be 1.039 OG and 1.008 FG

Mine was 1.046 OG and 1.024 FG ( I added an extra lb to the grain bill)


SWSBO Slayer should be 1.057 OG and 1.008 FG

Mine was 1.051 OG and 1.026 FG


I'm suspecting I may have under pitched, but I did make starters for both batches with washed yeast from previous batches.

 

[FastAndy]

Don't take this the wrong way but are you 100% per confident in your yeast washing process? sounds to me like maybe the yeast was mostly the first to flocculate from the previous batches and are leaving the beer with a higher than planned FG. Its possible that it could just be lagging and needs more time.

good luck,

 

[Rockindaddy]

That certainly is a possibility. When I made the starters they made krausen on top before I pitched, so everything "looked" OK.

 

[FastAndy]

Makes sense, and with that kind of krausen ring and drop in gravity they were definitely working for a some time. Maybe the yeast that made it through your washing process were from the bottom of the previous batches and are lazy. I'd wait it out a bit longer before repitching.

Cheers

 

[RM-MN]

What was the temperature of your mash and have you checked your thermometer for accuracy at mashing temperatures? I dropped a dial thermometer once and that made it read the temperature wrong so instead of a FG of 1.016, my beer finished at 1.002. You may simply be mashing too high resulting in so many unfermentables that the yeast can't break the wort down any lower.

 

[Rockindaddy]

I'm using a meat thermometer, so I should check the accuracy of it. Both were mashed at 150.

 

[awshucks5]

I would be weary of a meat thermometer. I would highly suggest a thermometer that has graduations for every 2 degrees

 

[dbsmith]

Hmm...either your readings are incorrect or perhaps your mashing temperature/time is wrong. The thermometer could be a problem. How long do you mash for? I usually mash for at least 50 minutes on all of my recipes. Do you stir your mash frequently to make sure that the heat is evenly dispersed? How do you mash? Do you leave it on the burner after you hit your temp?

 

[RM-MN]

Meat thermometers are not very accurate. They are fine for checking to see if your roast is done but for brewing you need a much more accurate thermometer. I have a couple Taylor digital thermometers, a dial thermometer, and a lab grade glass thermometer. I use the dial as I come toward strike temp because it is a bit more rugged but the lab grade is the one I use for that last few degrees to ensure accuracy. The digitals seem to be pretty accurate too so I use them to tell the mash temp because I can get a reading within a few seconds.

 

[duboman]

+1 to mash temp being too high and also could be the grain bill. Perhaps you can list ingredients and amounts. You may have too many less ferment able specialty grains as well.

Also, what yeast and how many washings?

 

[Beernik]

How long did you mash for? Did you check for full conversion?

 

[Rockindaddy]

I do stir my mash about every 15 minutes. I also mashed for 90 minutes instead of the 60 in the recipe, but that's because I do BIAB. When I mash, I turn off the burner after it hits strike temp and just leave it. It seems to hold the temperature for the entire time since I brew in the garage and it is summer. The recipes are here:

https://www.homebrewtalk.com/f66/centennial-blonde-simple-4-all-grain-5-10-gall-42841/

https://www.homebrewtalk.com/f71/swmbo-slayer-belgian-blonde-26599/

I'm not sure how to check for full conversion as I'm still pretty new.

 

[Beernik]

You spoon out a little wort and put it on a white plate. Put a drop of iodine in it. If the iodine stays light colored, all the starches have converted to sugars. If the iodine turns black, there are still unconverted starches in the mash.

90 minutes at 150F should be enough time to guarantee conversion.

I'm with everyone else, it has to be the thermometer. I can't think of anything else.

 

[tochsner]

I have 3 meat thermometers for the BBQ. After reading this I went and checked them against my Thermapen. On my 116* tap water, one read 109* and the other two read 108*. Maybe they do that so you don't under cook your meat or maybe they just aren't accurate. I would definitely check yours and see if you are mashing in the high 150's. That would cause your problem.

 

[Rockindaddy]

Any good recommendations for thermometers? Looks like I'm going shopping.

 

[TrickyDick]

Any good recommendations for thermometers? Looks like I'm going shopping.

Thermapen. It's simply awesome, and not just for brewing. But beware, expensive and only splash proof, not submersible.

TD

 

[TrickyDick]

You spoon out a little wort and put it on a white plate. Put a drop of iodine in it. If the iodine stays light colored, all the starches have converted to sugars. If the iodine turns black, there are still unconverted starches in the mash.

90 minutes at 150F should be enough time to guarantee conversion.

I'm with everyone else, it has to be the thermometer. I can't think of anything else.

I had problems doing this test. Turns out the iodine solution has a definite shelf life. I get the expired lugol's solution for work to keep mine fresh. The expired date for medical purposes is still fine for brewing, also, I use a piece of white chalk to test with as opposed to a plate. I bought a huge box of railroad chalk for this purpose. Also just use 1 drop of solution and of wort and slightly overlap them so you can get a "control" color. Braukaiser site has nice pics of this. It is possible to rinse the iodine out of the chalk and the wort as well if you use too much volume.

For me that has been easier. By the way, be sure that the sample you collect for testing is pretty clear, in other words no grain pieces.

Also some specialty malts will still show a slight reaction in your mash.

Reason I like the chalk is I can use several pieces or just flip the piece and use opposite end. Makes comparing my dough in sample to my 15 minute sample test easy to visually compare. I find conversion for most single rest mashes is done far before 60 minutes.

TD

 

[RM-MN]

I do stir my mash about every 15 minutes. I also mashed for 90 minutes instead of the 60 in the recipe, but that's because I do BIAB. When I mash, I turn off the burner after it hits strike temp and just leave it. It seems to hold the temperature for the entire time since I brew in the garage and it is summer. The recipes are here:

https://www.homebrewtalk.com/f66/centennial-blonde-simple-4-all-grain-5-10-gall-42841/

https://www.homebrewtalk.com/f71/swmbo-slayer-belgian-blonde-26599/

I'm not sure how to check for full conversion as I'm still pretty new.

I also do BIAB but I only do a 30 minute mash. On the one batch I used the iodine test, I intended to sample every 5 minutes to see when the conversion would indicate no starch left and to mash until that happened. The sample at mash-in showed starch but I got distracted and my next sample was at 7 minutes instead of 5 but it showed negative for starch already. I let that batch go for the 30 minutes and never got an indication of starch again. I tend to overshoot my OG but finish as low or lower than predicted so I'm not just converting to the long chain sugars that would indicate only alpha amylase was active but am getting the activity of the beta amylase too.