Difficulties reaching FG target

What are the main causes for getting a too high final gravity. Very often my FG ends up to high even though my brewday went according to plan and recipe. I have fairly good control on the mashing temeratures and the OG is where it should be, but still I have this problem almost every time.

How many points high are we talking about?

In approximate order of liklihood (although this order is certainly debatable):

• To high a mash temperature (inaccurate thermometer)  --- decrease your mash temp by 5F and see what happens.
• Temperature fluctuations during fermentation --- temperature swings can cause the yeast to drop out too soon and not finish the job.  the solution to this depends on the cause. 
• Fermentation Temperature too low --- ensure fermenter is at the correct temperature for the chosen strain. 
• Poor yeast health --- Make a starter on a sitrplate, with yeast nutrient
• Poor wort aeration - get an aeration/oxygenation setup
• Underpitching - Make a starter (or the correct size) on a stirplate with yeast nutrient (see mrmalty.com)
• Poor yeast nutrition - Add yeast nutrient at the end of the boil (servomyces or equiv)
  

+1 to Tom's list. Those are the variables that can raise final gravity.

Procedurally, are you making sure that your sample is degassed when you take the hydrometer reading? You simply spin the hydrometer to get the gas bubbles off the glass bulb. Those will float the hydrometer up.

Another potential explanation:  underestimating what your FG will be. 

Among other things, Beersmith uses the attenuation range published by the lab to estimate FG.  It is very possible to attenuate at the upper end of the range or even moderately higher than the published range--which would result in a higher than predicted FG.  Higher or lower than estimated FG does not necessarily indicate a problem with your process, although it certainly could. 

After you get enough experience with a given yeast and a good track record of performance (simply put: good tasting beer), you can adjust the attenuation range in your recipe to reflect performance in your brewhouse.  For example, the published range for 1056 is 73-77%.  Having brewed with it numerous times, I know that I typically get 80-84% apparent attenuation and tasty beers.  When I use 1056 in a recipe, I adjust the assumption to 80-84% to more accurately predict FG.

What is the apparent attenuation when you exceed predicted FG and how does this compare with the published range?  Do you experience this with all strains or a certain one?  Which one(s)?  How does your beer taste? 

All good recommendations,  however you have made no mention of your brewday volumes. Look at your pre and post boil, fermentation, and bottling volumes. Are they what you planned for.  Have you boiled off to much wort?

GoodisBeer said:

All good recommendations,  however you have made no mention of your brewday volumes. Look at your pre and post boil, fermentation, and bottling volumes. Are they what you planned for.  Have you boiled off to much wort?

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I would think the same if he said he was missing OG, but sounds like that's not the case.

Thanks for all comments!

I often end up 3-6 points too high. FG 1013 when BS target is 1010 and 1021 when target is 1015. I'm unsure if I have calculated the attenuation correctly, but I believe I'm below the range given on the yeast packs. I will check and revert.

I think I have good control og my mash temperatures and I've checked my termometer. I also believe my ferementation temps are OK. My boil off is stable around 10,5%. I normally use yeast nutrition and a yeast starter with stir plate. I havn't run my starter continously though, so I might underpich. I will try that next time. It could also be that the wort aeration has been insufficient. Last time I used and "paint mixer" creating a large whirpool for some minutes after I added the yeast. How do you do this part?

thassum said:

I also believe my fermentation temps are OK. My boil off is stable around 10,5%. I normally use yeast nutrition and a yeast starter with stir plate. I haven't run my starter continuously though, so I might underpich. I will try that next time. It could also be that the wort aeration has been insufficient. Last time I used and "paint mixer" creating a large whirpool for some minutes after I added the yeast. How do you do this part?

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Hi Thassum,
Using a paint mixer creating a large whirlpool for some minutes both straight after I pitch the yeast (yeast starter) and a couple of hours later (8-12 hrs) always worked for me.
I was wondering one thing: perhaps you are going too fast from primary to secondary based on the recipies you are using and causing a fermentation/temperature problem as Tom H was referring to. A suggestion could be to let the yeast sit in primary and ignore the secondary in your recipe next time. In addition be patience and use longer fermentation times then you would expect/like to use (ignore fermentation steps and recommended primary/secondary times in your recipes). Monitor fermentation and trust your own observations
R, Slurk

If you are landing below the attenuation range of the yeast, this likely indicates a problem with your process.  A stir plate should be run continuously, however this should generally only be needed for up to 24 hours.  I highly recommend trying that on your next batch. 

I aerate using an oxygen cylinder purchased from the welding supply section of a hardware store.  It is not critical to use oxygen.  I just do it because it's easy and fast.  I always end at or above the top of the attenuation range for a given yeast strain.

As Slurk says above, make sure fermentation is complete before moving the beer off the yeast cake.  I normally don't even check the gravity on a batch until after two weeks. 

What mash temperature do you typically use?  You are brewing all-grain, not partial mash--right?  What yeast strains are you having this problem with?  Some strains are a bit lazy and may need to be roused periodically to complete fermentation.

If you are getting a good conversion of your mash, and you mash temps are per recipe, and remain there during the mash, then I think your main problem is either in the yeast or the temp of your fermentation.

Does your fermentation area keep a constant temp?
do you take the temp of your fermentation from the fermentator or the room? The temp in the fermetator will be a few degrees higher than the room temp. and fluctuating temps is not that good.

Do you use a yeast starter? and how much per 5 gallon? Are you using a yeast nutrient?

ok, how about caramelizing of the wort? that would make some sugars unfermentable.

I found that when I started using starters that it was one of the biggest steps I ever had to stabilizing fermentation of my beers. I use 2000 ml starter per 5 gallons, use a stir plate, and yeast nutrient. My beers take off fast and finish on target. The outside of my fermentor is insulated to help keep it from accidentally having temperature fluctuations. And I have an old cooler I use as a fermentation/ Lagering closet.

the biggest thing to understand is that there is both a learning curve, and equipment curve to brewing beer. The more you brew, the more you learn techniques, the more you learn, and that helps so much. But also you need to have a eye out for stuff you can turn into brewing equipment. Finding a small cooler that you can put a good controller on to use as a fermentation closet will vastly help in your fermentations.  Not only that but you have a lagering closet also.

If you do not want to invest into such a closet, well remember we are all just having fun and many of us do not use them for a lot of reasons, the biggest being expense or space requirements.

and as always, keep notes on all things, no matter how minute, as you change things so you know what is working and what is not. A huge mistake made by way to many brewers is not making notes.

but the biggest thing to remember is to have fun and drink beer. As you get better, and as your beers do to, you will figure out that this is just part of the process of learning so reread this thread, they have posted a lot of good info, and start your changes as you can afford them. You can make starters without a stir plate, one step at a time.

Thanks once again for all good tips and suggetions.

I have been making starters from my first batch and I typically do a 2L for a 6 gallon batch. The fermentation has always started quickly. I've will keep my stir plate running the intire 18-24 hours. I brew all-grain and a normally mash between 66 and 69C degrees depending on recipe. I've also hired a BrauMeister and then the mashing temperatur was very stable.

It could very well be the fermentation temps causing my problem, and that I need to measure the beer and not only the room temp. Is it generally good to insulate the fermentation bucket? I most often ferment in the lower temp range given on the yeast pack but never below.

Another teory I have is that using proctafloc might stop fermentation a little early. In other words the beer gets clear before the yeast is completely done.

thassum said:

Thanks once again for all good tips and suggetions.

It could very well be the fermentation temps causing my problem, and that I need to measure the beer and not only the room temp. Is it generally good to insulate the fermentation bucket? I most often ferment in the lower temp range given on the yeast pack but never below.

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ding, ding, ding.

Are you CONTROLLING the temperature of the room?  The beer temperature will vary between 0 and 5C )0 to 10F) above the room temperature.  This will vary based on the rate of fermentation.  So, when fermentation is going like gangbusters (literally hot and heavy), the beer will be quite a bit hotter than the room.  As fermentation passes the half-way point and begins to slow down, then temperature will begin to fall back towards room temperature.  As the temp falls, the yeast will slow down more, and the temperature will fall even faster.  This rapid drop in temperature can cause the yeast to go dormant, and just give up on those last little bits of wort...leaving your beer slightly sweeter than it could have been.

The above assumes a constant room temperature.

For most yeast, the ideal beer temperature profile is a slow rise from midway through fermentation to end of about 2.7C or 5F.  Here is my profile from my last kolsch.  This is actual data measured and recorded from the batch. 


Recipe predicted FG was 1.009.  So, I ended up 1 point low.  The temperatures are measured using the temp probe of my controller.  It is taped to the side of my fermenter and covered in a 1 inch thick layer of reflectix insulation, which is also sealed with tape to the side of the fermenter. 

Another teory I have is that using proctafloc might stop fermentation a little early. In other words the beer gets clear before the yeast is completely done.

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No.  Protafloc, whirlfloc, irish moss will not affect fermentation.  These simply assist with creating a clearer wort out of the kettle.  They have no affect on fermentation or FG.

I need to measure the beer and not only the room temp.

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I use those "fermometer" adhesive strip thermometers on my fermentation vessels.  In my experience ales tend to be two to four degrees (F) above ambient, while I've seen lagers above by as much as six. In fact, that's a factor in how I judge fermentation is complete. When the brew temp and the room temp start to equalize, I know the yeast is getting done.

Thanks Tom and Maine HB! I really think I'm closing in on the problem now

I especially belive my room temp have been to high the first days. I brewed three batches with WLP029 (Kolsch) this autumn starting at OG 1048 and ending up with FG 1013. The first two days the room temp was 22C and for the rest of the fermetation it was 18C, so that must have been far two much! At least in the beginning, and I didn't increace the temp at the end either. Did you use the same yeast Tom? If not, which one did you use?

I will for sure start measuring the wort temperature directly instead. I have an old refridgerator and eletric probe/wire which shut on and of the power according too the set temperature. I thought I could put the probe in the wort and seal the fermentor, and in that way control the wort temp quite exatly. A thin plastic cylinder will protect the probe from the wort. Does this seem like a good idea?

/Tore

They make bungs with two holes in them for just what you want to do.  One hole is for the airlock and the other hole is for your temp probe.

A 4c drop is huge. That will definitely affect fermentation. 

For kolsch I use wlp029. I think you temps are too high for that yeast. I much prefer the profile above for kolsch.