Question on JZ's yeast pictch calc

[c0ff33d]

So my closest LHBS only sells yeast that is old, or even older. Picking through their stock the newest wyeast 3522 that they had was from August 30th of this year. The others they had there were back to April. According to the pitching calculator, I had a 62% viable yeast culture. The calculator says I should use two packs if I understand it correctly. Is it calculating that I need two packs based off of one packs viability percentage? If I found a fresh pack of yeast at a different LHBS w/90% viability would it be considered over pitching?

What is better, under pitching or over pitching yeast. Also, I wore pants during brewday, does this impact yeast viability?

[Mylo]

I think that JZ's calculator assumes that both vials are from the same date. Overpitching from vials? Hard to do. I wouldn't sweat it. I would recommend a starter for that old yeast. Besides growing cells, you will "proof" it as well.


Mylo

[c0ff33d]

Should I not bother pitching a second pack of yeast?

[Mylo]

I'd pitch them both into a starter 24 hours before your brewday.


Mylo

[BDawg]

Or you can step 1 package up twice. Start it in a 500ml starter,then after a day, pitch it into a 2 L starter.

[SacoDeToro]

Old and even expired yeast can be propped up just fine if you have the equipment to do it incrementally. I've stepped up a vial of White Labs Burton ale yeast that was almost 3 years old for a 12 gallon batch. It fermented just fine with no problems. That said, the vial had be in my fridge the entire time.