Originally Posted by barhoc11
I guess my question is, how do you know when you have enough yeast?
The best you can do is estimate. The yeast doubling time (under optimum condition) is 1.5 to 2 hours.
If you have a very large quantity of yeast cells, then you won't get that kind of speed. It might take a whole 24 hours to double.
If you have a small amount of yeast (like the small amount from a few bottles of beer), then you'll get closer to the 1.5 to 2 hours of doubling time.
Under perfect conditions, you could theoretically go from 1 yeast cell to 100 billion yeast cells in just 3 days.
There is usually way more than 1 yeast cell in the bottom of a bottle-conditioned beer, but on the other hand, our yeast is not in perfect conditions.
So, what I do is check to see how long it takes for the starter to drop from the OG to the FG. If it takes longer than a day, I decant the liquid off the top and add fresh wort. I'll do this until I can get the starter wort to drop from OG to FG in just 24 hours.
With the Chimay White bottle, it took me about 1 week, and I replaced the wort 3 times.
Mathematically, using 6 bottles instead of 1 will only save you about 4 hours.