[jimrod]

I need to step up my starter one more time to get the correct yeast cell population. How long does it take to complete each step? Or how long do I leave the yeast on the stir plate before I decant and add more DME?

[Stevie]

It takes as long as it takes to be done. In my experience, ale yeast starters are done in 24-72 hours.

[Wort-H.O.G.]

I need to step up my starter one more time to get the correct yeast cell population. How long does it take to complete each step? Or how long do I leave the yeast on the stir plate before I decant and add more DME?

certainly depends - stir plate? OG? Yeast? yadayadayada. I'm generally done in 24 hours give or take a few.

[gmac]

I'm doing the same thing right now. I leave it until the krausen subsides. I'm on a stir plate too but you can still see foam on the edges and in the vortex. Usually 24 to 36 hrs for my 1.5L starter at 1.040 OG but it also depends how old the vial is. There can be some build up time before you see any action.

I pitched yesterday at 2 and it is going well now, 18 hrs later but I've had lagers take a long time and over due vials take 48 hrs to see activity. I intend to crash tonight and step it tomorrow AM for a beer on Sunday.

[S. cerevisiae]

Ideally, one wants to step at high krausen.  Stepping at high krausen ensures that the culture is in peak health with ample ergosterol and unsaturated fatty acid (UFA) stores.  Waiting until the krausen falls ensures that the culture has entered the stationary phase where the cells will have to rebuild their ergosterol and UFA stores when stepped (i.e., the culture will have to go through another lag period).   If one wants to decant the supernatant (the clear liquid above of the solids) before pitching, one should force the yeast out of suspension at high krausen by chilling the culture.   This practice mimics the practice of cropping yeast at high krausen

As an aside, one of the reasons why skimmed top-cropping yeast can be repitched almost indefinitely is because it is cropped at peak health (Harvey's in the UK has repitched the same culture for over fifty years).  The practice of skimming also tends to naturally separate domesticated yeast from wild yeast and bacteria.  Dr. Max Emil Julius Delbrück developed a technique that mimicked the effect of top-cropping for non-top-cropping yeast strains that he referred to as "natural pure culturing" (a take on natural selection).  Max Emil Julius Delbrück duked it out with Emil Christian Hansen during the introduction of lab-isolated pure cultures.  Delbrück's method had the advantage of not requiring a propagator.

[gmac]

Ideally, one wants to step at high krausen.  Stepping at high krausen ensures that the culture is in peak health with ample ergosterol and unsaturated fatty acid (UFA) stores. 

Good to know. I've waited until krausen drops based on absolutely nothing but an assumption that division would have been completed by then.  I will cold crash the next one at high krausen.  With no way to quantify the yeast population, I am sure that both ways will be better than nothing.

[beersk]

I usually give mine 3 or 4 days, crash cool, decant, then add the step up wort, give that 2-4 days, crash cool, decant and pitch into wort. I do my step up starters a week and a half in advance, typically. It's kind of a pain, but ya gotta do what ya gotta do, I guess. I might try was S. cerevisiae suggested and just pitch the step up wort on top of the starter that's going and skip the first crash cool step.

[S. cerevisiae]

It should not take more than a day under the worse conditions to propagate the contents of a White Labs tube to a culture that is large enough to pitch five gallons of high-gravity beer or ten gallons of normal gravity beer.  I can grow a loop or two of yeast taken from a slant to a pitchable culture in two to three days.

Yeast cells divide approximately every ninety minutes during the log phase, which means that the cell count increases approximately by a factor of 2¹⁶ (65536) every 24 hours until the media is exhausted or maximum cell density has been reached, which is approximately 2 x 10⁸ (200 million) cells per milliter for S. cerevisiae.  The maximum cell density that 1L of wort can support is 1000 x 2 x 10⁸  (200 billion) cells.  The average White Labs tube contains 70 billion viable cells, which means that a 1L starter can only support a 3-fold cell count increase before maximum cell density has been hit.   Accounting for normal cell death, a 200 billion cell culture can be propagated from a White Labs tube in less than eight hours.

[theoman]

What's the consensus on lager yeast?