Testing the limits of yeast viability

[philipCT]

For the curious, here's how I'm calculating the starter...

First of all, I'll start with 5.5 gallons of 1.052 wort. The calculator estimates I need 201Bn cells.

Most sources say a 6 month old smack pack is 0% viable. But we know better but I'm not overly optimistic, so I started with the assumption of 10% viability. I use BrewersFriend.com for multi-stage starters and it's always worked well. For this, I just input different yeast-mfg-dates until the calculator said 10% and went from there.

After a 1L, 1.017 starter on a spin plate the estimate was that I had 78Bn cells.

After pitching that starter to a 2L, 1.036 starter, it estimated I had 365Bn cells.

So that's a healthy percentage (something like 75%) over the recommended pitching rate. I figure these are all ball-park estimates, and that even at that, I'm not risking over pitching by a enough of a margin to worry about.

Onward!

 

[mdbrewer1]

I revived a vial of WLP029 that was 4 months past its use by date this past weekend. Pitched it into 1.020 wort and it perked up within a day. I let it finish, and since I plan to use it next month, I poured the good stuff into a Mason jar and tossed it in the fridge. I'll do a starter with 1.040 wort prior to brew day and let it rip.

 

[philipCT]

Update: after pitching the decanted yeast from the second stage starter into 5g of well-aerated wort, I had a strong fast-start (6 hours) fermentation with about 1/4 qt of blowoff through a big blowoff tube - and that was after 10 drops of fermcap. I maintained temp at 65F.

So far so good - at least it's making all the right signs for a healthy fermentation!