High gravity fermentation incomplete

[freeflydude]

I have done several brews in the higher gravity range and they all tend to finish high. The biggest has been my last one at 1.110 OG but only got down to 1.031 FG. Does anyone have suggestions on how to get a high gravity brew to ferment to completion? I have done everything right as far as I know. I use yeastcalc to figure out starter size and get my pitching rate correct. I generally try to overpitch a little. I add yeast nutrients during the boil and pure O2 to the wort before pitching yeast. I even add a second shot of O2 for the really high gravity wort at about 12-18 hours. I let the 1.110 ferment for about 18 days before kegging and probably should have let it go longer but I doubt it would have gone down the the 1.016 or so that it should have been since it wasn't blowing off bubbles at that point. Here's the recipe info:

12.5lb Pilsen
1lb CaraMunich
1/2lb Biscuit
.33lb Aromatic
.25lb Special B
.19lb Chocolate
3lb Dark Candy Sugar
1oz Northern brewer hops (90)
1oz Styrian Goldings hops (15)
1oz Hallertauer hops (15)
WLP530 Abbey Ale yeast (high alcohol tolerant)

Do any of you high gravity brewers have advise? Do you usually have to pitch another yeast to get your fermentations to completion when they are that high?

 

[Dynachrome]

Your mash twmps will make a difference also. Some guys will agitate the fermentor.

It looks like your thread title was decent.

Check out the threads at the bottom of the page. They are linked from your thread title.

 

[duboman]

You are currently at 73% attenuation and the yeast is rated between 75-80%. What temperature did you mash at and are you sure your thermometer is calibrated and accurate? If you mashed high then your wort was less fermentable resulting in a higher then desired FG and less attenuation.

If you do decide to re-pitch you will need to do so with a fresh starter at high krausen to tolerate the present level of alcohol. You can also try to raise the temperature and rouse the yeast. Many times with beers this large the yeast can take quite a while to eek out those last several points and raising the temp can help them keep busy, especially with yeast rated to high flocculate.

 

[beergolf]

For big brews like that I often hold the sugar back. Pitch the yeast and let it work for a few days until fermentation shows signs of slowing down. Add some of the sugar, and let it go for a few more days. Add some more sugar and let it go. Watch the temp so it does not drop and it should finish a lot lower. The theory is to let the yeast eat the harder to ferment sugars and then feed it the simple sugars later. A lot like telling a kid that they cannot have desert until they eat their dinner.

I recently did a 1.097 BDSA and used that technique and it is down to 1.010. Tastes amazing. It also had 3 lbs of sugar. I did three additions.

Try it next time you brew a big beer with a lot of sugar in the recipe.

 

[Cyclman]

18 days probably isn't adequate. Raise the temp 2/3 of the way through ferm to the high end of the range for the yeast, that'll get you a few hundredths.

 

[Calder]

1.031 is awful. If you remove the candi sugar which will ferment completely, you only got 65% attenuation.

My suspicion is that you mashed too high. You should have been about 148 F for that beer. Alternatively, you fermented too low, and the yeast stalled as it slowed down when the temperature dropped.

 

[freeflydude]

Fermentation was in the mid to high 70s. I did try to raise the temp a bit at the end but maybe not enough. Mash temp was on the high end in the mid to upper 150s. I'll lower the temp on the next one. How do you add the simple sugars during fermentation? I always add to the boil. Thanks for all the advice.

 

[Calder]

Mash temp was on the high end in the mid to upper 150s.

How do you add the simple sugars during fermentation? I always add to the boil. Thanks for all the advice.

Mash temp is your problem. Drop that by 10 degrees next time and you should be good.

Dissolve the sugar in a little water and boil for a few minutes and then add to the fermenter. Add as fermentation slows down.

 

[Pscdouglas]

You'll also need to give the yeast more time than normal, as others have stated. Big beers that I brew get a primary of no less than 5 weeks. Rouse the yeast twice a week or every day if you can remember. I have a Stone Old Guardian BW that has been in primary for 4 weeks with Denny's Fav 50 and it is still pushing a bubble out of the airlock every few minutes. OG 1.100. 1st week:1.040 2nd week: 1.030 3rd week: 1.026 4th week: 1.022. looking for a FG of around 1.017.

 

[beergolf]

I just re- read the original post. You kegged it after 18 days. That is way too short for a beer that big with that yeast. That yeast can take a long time to get the last few points.

Here is a good quote from Brew Like a Monk....


"Let the ferntation finish, perhaps at a higher temperature. It may take as long to get the last few points of attenuation as it did for the first 80%."

If you cooled it down after kegging it will not go lower because the yeast will quit.

Chris White of White Labs yeast, says of Belgian yeasts.*

*"When you cool them, they stop. They go into survival mode. You can try rousing them, raising the temperature, but they won't start again. You just have to add new yeast."

 

[homebrewdad]

A few things that also might help:

Piitch enough yeast. Make a monster starter.

Aerate properly.

Consider yeast nutrient or similar.

Start your fermentation on the lower end of the range and ramp it up with time. Belgian yeasts can take some high temperatures, especially towards the end (upper 70s, even 80ish).

Save your simple sugars and add it to the fermenter when you are ~half attenuated.

 

[CDGoin]

Save your simple sugars and add it to the fermenter when you are ~half attenuated.

Hmm.. so your saying in some cases I could add my honey to my Marzen after the Krausen has formed ..? Hmm... MY try that next batch.

 

[homebrewdad]

Hmm.. so your saying in some cases I could add my honey to my Marzen after the Krausen has formed ..? Hmm... MY try that next batch.

Sure you can. This is a nice trick for keeping the yeast going. Let them work on the more complex malt sugars first, then when they start to tire out, give them simple sugars.

 

[CDGoin]

Definately will try that next time.. I would think it would keep the honey flavors better.

Now I did try the honey in the secondary.. after fermentation was almost done and after a D-Rest.. but havent finished that one.