How to tell if my yeast starter is actually propagating properly?

[Geordan]

I picked up a smackpack of W2112 today, only to realize when I got it home that it was packaged back in November -- according to YeastCalc and the Mr. Malty Calc, that puts it at about 10% viability. Ugh. Seller agreed to replace it to no problems -- great service -- but I'm a fair clip from the store and won't be able to pick it up until next week, which pushes my brewing back quite a bit.

According to YeastCalc, I can do a stepped starter -- 1L then 2L -- to grow up an appropriate pitch for my 5 gallon 1.052 batch of California Common. I've gone ahead and made a 1L starter and it's spinning away on my stir plate (smacked the pack about 4 hours before pitching; it swelled a little bit, but not much), but my main concern is that I've only every made 2 starters before, and both were with very fresh yeast and no stepping, so I don't have the experience to tell if my endeavours are successful until I find out the hard way!

I figure I'll leave the 1L step on the stir plate for about 24 hours, crash it in the fridge overnight, then run the 2L step for another 24 hours. However, I have no practical way of telling if the process is actually creating useful yeast! I marked 100mL levels on my e-flask, so I should be able to get a rough estimate of yeast slurry volume during crashes, but does that actually help me at all? Does anyone have a bead on the best way to estimate whether I've hit the 250b healthy cells I need for a sufficient pitch?

All advice appreciated -- thanks!

 

[wolfman_48442]

If I'm bringing yeast back like that, I will usually devote several days to the process, stepping up just like you said.

I'd let the first step run at least 48 hours. 72 hours is not unreasonable for the first step using old yeast.

You should see a small krausen ring in the flask by at least 36 hours, hopefully sooner. If you don't see any krausen, you have dead yeast.
Let that run until you don't see any CO2 being released, then cold crash.

Decant most of the used wort, add fresh, sterile wort to your desired final volume, and be prepared to have crazy amounts of krausen trying to leap out of the flask.
Let this run 24 hours and you'll be ready to pitch some yeast that are eager to attack your wort.

 

[Rbeckett]

Wolf,
Thanks for the guide lines. I was afraid to ask and demonstrate my ignorence but I guess I just gave it away anyway. Great answer to a really great question. Thanks guys.
Bob