# Raising/dropping Temp At The End Of A Ferment



## gava (20/8/09)

Hello All,

I've been searching around and have come across some people that either raise the temp or drop the temp at the end of a ferment..

why is this? which is better? what does this do? and what temps are suitable? anything else I should know?

(got two brews about to finish ones a Golden Ale another is a hefeweizen)

cheers for your info..


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## razz (20/8/09)

Usually drop the temp to crash chill a beer before adding polyclar at 0-2 degrees. I sometimes up the ferment near the end of a brew to reduce diacetyl, but not often. Only if I can taste diacetyl.


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## QldKev (20/8/09)

I also do both, add a couple of degrees to help ensure it is fermented out (lagers also help clean up diacetyl); and then drop it to 2-3 deg for a few days to help drop the yeast out of suspension. 

QldKev


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## floppinab (20/8/09)

Yep, depends a bit on what you are brewing.

For an ale like your Goldy, let it ferment out as usual at the usual ale temps then many (myself) included throw the fermenter in the fridge for a few days @ 2 -5 deg. This helps drop/compact the yeast out into the bottom of the fermenter and clears your beer a bit before bottling/kegging and without necessarily using a secondary. Don't see too much value in raising the temp from your standard ale temps prior to throwing it in the fridge, could be wrong there though.

For a lager, bring the temp up from your lager ferment temp of 10 odd degs to something like 17 deg for a day or two. This helps get drop those last few points of sugar out of your beer and clears diacetyl and other lager fermentation unwanted flavours. Then as QLDKev suggested into the fridge as per above for the same reason.


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## Screwtop (20/8/09)

For ales - after fermentetion is complete leave on the yeast for one week for the yeast to clean up after itself at fermentation temp, then drop temp to around 2. For 2 reasons, drops any non-floc'd yeast out of suspension ready for kegging, and cold temps lessen risk of infection and I may not be ready to keg at the time, so the beer waits at 2C. 

Cheers,

Screwy


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## crundle (20/8/09)

I like to warm all my beers up a touch at the end of fermentation for a day or so to help clean up any diacetyl (more important in lagers) and to help the yeast finish off the job, and maybe get a point or two further down on gravity (especially if it has stuck at some point, along with a good shake to re-flocculate the yeast).

Then for kegging and bottling I like to crash chill the fermenter for a day or two to drop out any yeast and clear up my beer (never used any clearing agent yet). I would mention that if you are bottling, there can be issues in leaving the beer too long in the fridge before bottling, as you may find the only yeast left in your beer is that which just wont flocculate out, and this may be a negative for bottle conditioning as the yeast may take much longer to carbonate your beer or worse still, may not carbonate it much at all.

I find with kegging that after two weeks in the keg in a kegerator, my beers are normally very clear anyway.

cheers,

Crundle


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## Jonez (15/9/09)

crundle said:


> I like to warm all my beers up a touch at the end of fermentation for a day or so to help clean up any diacetyl (more important in lagers) and to help the yeast finish off the job, and maybe get a point or two further down on gravity (especially if it has stuck at some point, along with a good shake to re-flocculate the yeast).
> 
> Then for kegging and bottling I like to crash chill the fermenter for a day or two to drop out any yeast and clear up my beer (never used any clearing agent yet). I would mention that if you are bottling, there can be issues in leaving the beer too long in the fridge before bottling, as you may find the only yeast left in your beer is that which just wont flocculate out, and this may be a negative for bottle conditioning as the yeast may take much longer to carbonate your beer or worse still, may not carbonate it much at all.
> 
> ...



I assume you don't bottle but if you did, would you bring the beer to room temp (say 20C) for priming after crash chill or would you use conversion tables to work out the amount of priming sugar?


Edit: sorry, reviving this thread. Just found it in a search


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## manticle (15/9/09)

Screwtop said:


> For ales - after fermentetion is complete leave on the yeast for one week for the yeast to clean up after itself at fermentation temp, then drop temp to around 2. For 2 reasons, drops any non-floc'd yeast out of suspension ready for kegging, and cold temps lessen risk of infection and I may not be ready to keg at the time, so the beer waits at 2C.
> 
> Cheers,
> 
> Screwy



Fairly similar to what I do. I hit stable gravity and leave it for a few days(between 3 and 7 depending on fridge room, time etc) , then crash chill for 5-7 days. Not only do I end up with clearer beer (more than cosmetic - sedimant has a flavour impact) but the cold conditioning seems to accelerate the maturation process. Last week my golden ale tasted like bananas and baby vomit - this week (3 days into cold condition) it tastes like beer with citrus hops.

Neither is better as they form different functions - raising temp is for lagers to reduce diacetyl and/or lagers and ales to encourage dropping the last few gravity points. Reducing temp is to drop out yeast and help with maturation/cleaning.

Raising ferment temps DURING primary is only just something I've started to fiddle with and is a different thing again - encouraging certain ester production from certain yeasts in certain styles.

@Jonez - Aug the 20th isn't so far away you couldn't be accused of necro-threading.


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## Jonez (15/9/09)

manticle said:


> Fairly similar to what I do. I hit stable gravity and leave it for a few days(between 3 and 7 depending on fridge room, time etc) , then crash chill for 5-7 days. Not only do I end up with clearer beer (more than cosmetic - sedimant has a flavour impact) but the cold conditioning seems to accelerate the maturation process. Last week my golden ale tasted like bananas and baby vomit - this week (3 days into cold condition) it tastes like beer with citrus hops.
> 
> Neither is better as they form different functions - raising temp is for lagers to reduce diacetyl and/or lagers and ales to encourage dropping the last few gravity points. Reducing temp is to drop out yeast and help with maturation/cleaning.
> 
> ...



Well you see. I was trying to do the right thing by not asking a question before searching for diacetyl.

Found this thread the most convenient because it touches on ales which I am fermenting at the moment. It has been at 18C for a fortnight now and still in 2010 so I thought I would raise temp and maybe clear diacetyl. As many have pointed out here. But my question has to do more with whether I bother doing crash chill or not given that I will be bottling.


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## manticle (15/9/09)

Jonez said:


> Well you see. I was trying to do the right thing by not asking a question before searching for diacetyl.
> 
> Found this thread the most convenient because it touches on ales which I am fermenting at the moment. It has been at 18C for a fortnight now and still in 2010 so I thought I would raise temp and maybe clear diacetyl. As many have pointed out here. But my question has to do more with whether I bother doing crash chill or not given that I will be bottling.



Sorry I meant COULDN"T be accused. Post now edited.

Sausage fingers


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## manticle (15/9/09)

And crash chilling/cold conditioning is one of the best things I have ever done for my beers.


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## Jonez (15/9/09)

manticle said:


> And crash chilling/cold conditioning is one of the best things I have ever done for my beers.



yeah, but i know you bottle. So do you raise temp again for bottling?


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## manticle (15/9/09)

I usually let the fermenter sit at ambient temps a couple of days before bottling but most people suggest this is unnecessary.


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## CDJ (15/9/09)

I just bottle and I raise the temp to what the original fermentation temperature was for a couple of weeks before returning the bottles into the fridge before drinking.


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## Jonez (15/9/09)

CDJ said:


> I just bottle and I raise the temp to what the original fermentation temperature was for a couple of weeks before returning the bottles into the fridge before drinking.



Let me explain better my concerns:
Do you bottle and then raise temp? what about bottle bombs? Summer is coming and it promises to be very hot so I am afraid if there is enough CO2 trapped in the cold beer they will explode once it gets warmer.

@ manticle. I suppose people who think it is not necessary are considering the bottling temperature when priming.


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## buttersd70 (15/9/09)

Jonez, the temp of the beer at the time of bottling is irrelevant. What is important is the temperature used for the calculation of the residual co2 post ferment. This is the highest temperature that the beer has been at from the end of fermentation onwards.
link


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## CDJ (15/9/09)

Your levels of CO2 after fermentation ended are dictated by your max temp during fermentation as I understand. There is a thread around but cannot find the link...



edit: thanks butters...


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## Jonez (15/9/09)

buttersd70 said:


> Jonez, the temp of the beer at the time of bottling is irrelevant. What is important is the temperature used for the calculation of the residual co2 post ferment. This is the highest temperature that the beer has been at from the end of fermentation onwards.
> link




I see...so when bottling you use the amount of sugars that correspond to the max temp of fermentation. (say 18C for an ale) independently of whether you may be bottling at 24C for example


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## buttersd70 (15/9/09)

Jonez said:


> I see...so when bottling you use the amount of sugars that correspond to the max temp of fermentation. (say 18C for an ale) independently of whether you may be bottling at 24C for example



Not quite. If the temp of the beer is _higher _that the max temp of the latter stages of fermentation, you use the higher....so, in your example, you would use 24C as the temp in a calculator.

You use the _highest _temp it reached at _any stage_ between the latter part of fermentation and bottling.

eg

ferment 18C, raise to 20C in last 24 hours of fermentation. Crash chill to 2C, condition. Take out of fridge to bottle......I would use 20C in the calculation, even though the temp of the beer _as I am bottling it_ is 2C


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## Jonez (15/9/09)

buttersd70 said:


> Not quite. If the temp of the beer is _higher _that the max temp of the latter stages of fermentation, you use the higher....so, in your example, you would use 24C as the temp in a calculator.
> 
> You use the _highest _temp it reached at _any stage_ between the latter part of fermentation and bottling.
> 
> ...



Ok thanks.. that's clear now.


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## hazard (15/9/09)

Jonez said:


> Ok thanks.. that's clear now.



Jonez, just think of your fermenter as a big bottle of coke. If you take the lid off a cold bottle, CO2 escapes, but there will still be some remaining carbonation. If you leave it in a warm place, it will continue to lose CO2 until equilibrium is reached (i learnt this in high school chemistry over 30 years ago so I'm a bit rusty, its got to do with partial pressure). If it gets hotter, more CO2 is lost until a new equilibrium point is reached.
But - if you put it back in the fridge - it cools down but will NOT carb up again. If you put it in a fridge which contained a CO2 atmosphere then yes, it wold re-ab absorb CO2 but this is highly unlikely ....
So as butters says, CO2 level is based on highest temp that is reached.


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## Jonez (16/9/09)

hazard said:


> Jonez, just think of your fermenter as a big bottle of coke. If you take the lid off a cold bottle, CO2 escapes, but there will still be some remaining carbonation. If you leave it in a warm place, it will continue to lose CO2 until equilibrium is reached (i learnt this in high school chemistry over 30 years ago so I'm a bit rusty, its got to do with partial pressure). If it gets hotter, more CO2 is lost until a new equilibrium point is reached.
> But - if you put it back in the fridge - it cools down but will NOT carb up again. If you put it in a fridge which contained a CO2 atmosphere then yes, it wold re-ab absorb CO2 but this is highly unlikely ....
> So as butters says, CO2 level is based on highest temp that is reached.



Hazard 
It is all understandable. I knew more CO2 will be released at higher temps and so on. However we have to admit we are using an approximation method here. One example is a case where the higher temperature occurs at the beginning of the fermentation. Let’s say that the temp is then reduced for any given reasons and the most significant amount of CO2 is then produced at that lower temp. If the variations in temp are small, the differences may be neglect able. But everyone here does different, so it is always good to hear their opinions

edit spelling again


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## crundle (16/9/09)

Thanks for bringing up that question Jonez, I keg so I didn't know the answer, but now after hearing the explanation I do.

When I was bottling, I had my fair share of bombs, but my temperature control consisted of brewing downstairs at my parent's house in the Adelaide Hills, where it is partially built into the rock on a hill, so the temperatures were very steady the whole year around, but that was well before I learnt about the importance of fermentation temperatures and how they impact on bottling.

Kegging does make the whole thing simpler - set the pressure according to the kegerator temperature to hit your desired carbonation level and then bottle from the keg for clear perfectly carbonated beers.... in theory!

Crundle


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## HoppingMad (16/9/09)

Noticed you have a Hefeweizen going. 

Depending on the yeast you're using, some people will push the temp up towards the end to get more banana esters (to around 23/24 degrees). *Don't* do this unless you have checked the specs on your yeast first though! Some yeasts won't like going this high. But something like a Wyeast Weihanstephaner will give you more banana clove when pumped a little higher. Haven't tried it on a Fermentis WB-06, but have heard of it being done too.

If you like fruity esters in your beer, then these higher temps work. This is particularly so in a lot of Belgian styles and Saisons where it is common to ferment at regular ale or high ale temps then rocket the temp up to finish it off. It is a bit of a balancing act though - go too high and overstress the yeast and you will get nasty fusel alcohol notes in your beer - so follow the temp ranges recommended by the yeast supplier website.

Hopper.


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