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What's REALLY too cold?

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At what temp does fermentation cease with Ale yeast? I know different strains react differently but what is the rule of thumb. I was going strong at 69-70 degrees but slowed, possibly just due to being finished, when the temp dropped to 67- 68 degree's. It is Munton's Ale Yeast but I plan to try others.
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Bearcat Brewmeister

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I think the lowest fermenting temperature on an ale yeast is Wyeast 1728 (Scottish) which can go to about 55F. I typically use it in the low 60s for primary and upper 50s for secondary and add a few more days (10-20 instead of 7-14).
 

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I am not so sure about this. I use a thermowell in the fermenting beer to measure and adjust temperatures automatically. Historically, I have always fermented at 65 degrees and had wonderful luck with the process. On a recent batch, I tried fermenting at 60 degrees -- after three weeks in the primary I racked to my kegs to secondary. As I am lazy and use a long primary, I dont usually measure the FG during this time (you can probably see where this is leading). So after two weeks in the secondary I wanted to check the FG and low and behold it was only 25% fermented!

On the yeast side I used a 2 liter starter that had a large amount of yeast; so I knew the yeast was good. On the temperature side; I use a Ramco controller with a heating belt inside of a freezer.

So the ONLY delta was it was a medium / high gravity beer and 60 degrees.

20/20 hindsight, I should have started at 65 for the first few days and then gradually gone down to 60 degrees. But after reading the forums for years, I thought that 60 degrees was perfectly acceptable for ale yeasts. While maybe 60 degrees is fine for low gravity beers (and depending on the yeast strain; I used White Lab's Irish) ... I am going to stick with 65 degrees for most of my fermentation from now on. It maybe a little too high; but still ferments pretty clean.

Now I am stuck with 10 gallons of beer that is still fermenting in my 5 gallon kegs. What a mess when I blow off the tops of those (I already have all of my carboys full; so cant rack back into a carboy). Still funny though; I think laughing at yourself is a good thing in this hobby.
 

RoaringBrewer

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Started my current batch, using WL Abbey Ale Yeast (WLP 530?) at around 70F for a day to get the yeast active. Then dropped it into my basement where the carboy falls to around 58-60F at night... yeast are still plugging away fine.

Again, you already know the answer - all yeasts behave differently. However, I wouldn't worry about going below 67-68, almost all ale yeasts should behave fine into the lower 60s... some even can get into the 50s (although I wouldn't test this personally unless the yeast is known to ferment in the 50s).
 

Bearcat Brewmeister

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Kharz said:
I am going to stick with 65 degrees for most of my fermentation from now on. It maybe a little too high; but still ferments pretty clean.
Well, it is really strain-specific. If you use the same strain of ale yeast, use the same temperature. Most yeasts can perform over a large temperature range (and 65F should be in that range for most ale yeasts), but they are typically optimal in a three to five degree range - too cold and they slow too much like you found out, too warm and you develop off flavors. If you use many different ale strains on different batches, I would always double check the range for that yeast and use it instead of always using 65F.

White Lab's and Wyeast both list their optimal fermentation temperatures for each yeast strain they sell on their web site. The Irish ale yeast states 65F to 68F, so using your standard 65F method would hav been perfect this time. The Wyeast version of this strain mentions that it is active down to 62F, so at 60F, they just got a bit sleepy.
 
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Thanks for the replies> How about when you start at a higher temperature then drop down to a much lower temp, is there any affect on flavor?
 

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It depends on how much higher, how long before you drop it, how much you drop it, and how quickly you drop it. If it is too high for too long, you can get some sharp alcohol, solvent-like, or fruity flavors. How long is too long? Hard to say, but remember that once vigorous fermentation begins, most of it is done in the first 48 hours after that. Also remember that a byproduct of fermentation is heat, so if you have a wort that is too warm already, it will ferment fast and produce even more heat, compounding the problem of getting it down into the range you want. If that happens, you want to cool it fast. Problem is if you cool it too fast and too far, your yeast can shut down.

Best bet is to start your yeast in your wort near the middle to top of the listed range of the yeast (usually about 70F). If unmonitored, the heat produced by fermentation will easily heat the wort to 73F or 74F (possibly higher), so at the first signs of fermentation, start cooling the wort to the lower to middle part of the yeast's optimal temperature range (usually around 65F to 68F, but it varies). Note that to get it to 65F, your fermenter's external temperature needs to be cooler than that because of the counteracting heat produced by fermentation. A good way to do that is to put the carboy in a small water bath with a towel draped around it that is wicking water up from the water bath.
 
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