Fermentation temps for ales

A bit of confusion. I have brewed 3 batches thus far. The last two were partial grain.
I just received a catalog from Northern Brewer and in it it states that ales should be fermented between 60 and 72 degrees. I've read this before in other instructions.
The wyeast smack pack the came with my Oatmeal stout kit said 70-75 and I'm sure my last kit had a similar temp although it was a different yeast. I thought that was a little warm. It fermented great and long, took about ten days in primary at 72 degrees. It's now in secondary at roughly the same temp or slightly lower...70 deg.

What if I went lower on the temp? Say below 70...65-68? Does it matter on secondary? Would it matter on primary?


Tommy

Fermentation is a function of temperature, and all yeast have different temperatures, but they are all pretty much between 68 and 75F. The lower you go, the slower it will ferment, to a point. Then after that, they will die off. As you probably know, you'll need a lager yeast to get down into the 50 and 40's. I wouldn't go below 68. Once in the secondary, or clearing, carboy, temperature really doesn't matter, it's just used for clearing the brew.

The instructions from NB are generic instructions made to make life simpler and are fine. If you want to get more advanced, look at the information for the particular strain of yeast you are using. Each one has different characteristics, including a different temperature range.

Even within that range the same strain of yeast will exhibit different characteristics from low to high. Lower temperatures typically result in a slower, cleaner fermentation while higher temperatures typically result in a fruitier, more estery profile and a more rapid fermentation.

Erring too low will cause the fermentation to stall out or, at best, proceed very slowly. Erring too high will cause unwanted byproducts such as excessive esters and fusel alcohols to be produced.

I try to hit the middle of the yeast's temperature range for fermenting (and you frequently have to look this range up on the manufacturer's site), although just about any ale yeast will be ok 68-70F. If a ferment stalls, I bring it up to the top of the yeast's range for a few days. Ale yeasts won't actually die if the temperature is too cold, but they won't do any fermenting either.

Thanks...makes sense.

Tommy