Percentage of Final Attenuation During Primary Fermentation

I'm just wondering what percentage of my total attenuation should be happening during primary fermentation. I know that secondary fermentation is not "fermentation" per say, but mostly for clearing. That said, should I be expecting to achieve 100% of my desired attenutation during primary fermentation? 90%? 75%?

For my latest batch, I used White Labs California Ale V yeast. I pitched the yeast (1.5 liter starter started 3 days before) into a oxygen injected and cooled wort. The wort is kept in a temperature controlled 69 degree environment while fermenting. After a week in the fermenter, I've got about 65% attenuation. The normal "range" for the yeast is a low of 70 and a high of 75.

This 65% attenutation rate after a week seems average after a week of fermentation for the last 4-5 batches of beer I've made. Is that normal? For the batches I've moved to a secondary, I haven't seen the attenuation drop further, I'm assuming because I've taken the wort off the yeast cake and the suspended yeast isn't enough to keep the attenuation going. Have I moved it to early? Should I be racking some of the yeast cake over into the secondary fermenter?


I'm going to leave this batch on the yeast cake for another few days to see if the yeast keeps working. Am I experiencing "normal" attenuation, or should I be looking at my techniques and recipes to see if something is preventing attenuation in the "normal" range?

Look for 95%-100% of fermentation to be complete before racking. 65% attenuation is quite normal after a week in the fermenter.

Should I try to pick up at least some of the yeast cake off the bottom when I move to the secondary, to help finish the fermenting? Should the suspended yeast be able to finish it?

With my three batches, my beer seems to need 10 - 15 days to get full attenuation in the primary.

You will pick up plenty of yeast when you rack to the secondary. I wouldn't intentionally "try" to pick up yeast cake off the bottom. It will just mean you have to wait longer in the secondary for everything to settle out because you resuspended some trub.

There is nothing holy about racking after a week. Autolyse and oxidation are the two big buggaboos of homebrewing. Both of them take MONTHS to occur. You want to rack after the batch is done fermenting and at least in the low end of the attenuation range. Racking too soon leads to poor final attenuation.

Thanks everyone. I'll stick with my original plan and let it go in the primary for another week.