Fermentation Temps; too cold?

How cold is too cold for an ale? I am of the mind that unless activity stops or significantly slows due to low temps then it is warm enough. Am I wrong?

I've got an IPA fermenting. I put the fermentation bucket in my igloo cooler and filled it half way with cool water. I've been putting in small bottles of ice on occasion. The temperature of the water in the bath has been between 60 and 64. How does this sound?

It has everything to do with that particular yeast strain. Some ale yeasts are more cold tolerant than others. The general concensus is that ales fermented at the bottom of their range finish a little cleaner, similar to a lager, with less of the fruity esters associated with ales (and vice versa for wamer ferments).

It's also a matter of what you want out of it. The temps of your water bath on on the low end or below the preferred range of all the ale yeasts I'm aware of. That's not necessarily bad, but you will get a different beer that if you fermented in the high 60s or low 70s. Check the specs on the yeast strains you are considering. Nearly all of them are fairly accurate descriptions of what you can expect and what temperatures are preferred. Of course, they are all fairly vague and subjective (e.g., "makes a rounder, fruitier beer"), but they are accurate to that extent.

Keep in mind that, typically, lower temperatures lead to crisper, cleaner beers and that higher temperatures lead to rounder, fruitier beers. However, get outside a yeast's preferred range and bad things may happen. For example, temperatures that are too low may lead to a stuck fermentation or too much diacetyl left in the beer because yeasts don't metabolize it before you rack. Temperatures that are too high may lead to fusels, undesireable acetaldehydes, phenols, or overpowering esters that you did not care for.


TL

I've used Nottingham at 60 degrees and liked it- it was neutral and gave a cleaner tasting beer. Nottinghams packages says it ferments down to 57 degrees.

My house is pretty cold most of the time, so 60 degrees is pretty typical in the winter for me. The special pacman yeast also fermented very well at 60- I hope it comes out again this winter.

As long as there is activity, it isn't too cold. However, if you are using a highly flocculate yeast, there might not be enough action to keep it suspended. I tend to ferment about 1/4 of the way from the bottom of a yeast's range.