[Craig]

So I am curious about double pitching yeast. I have a stir plate so I am wondering if increasing the time on the plate would suffice, or just increasing the yeast starter would work or a combination of both?

[Bob357]

If you are talking about pitching twice as much yeast as a packet contains, that's what starters are for. There are several pitching rate calculators out there that will tell you how much yeast is needed for a batch based on volume, OG and whether it's am Ale or a Lager. They also tell you what starter volume you need and how much water and DME are needed to make it.

I use Homebrew dad's on-line calculator.

http://www.brewunited.com/yeast_calculator.php

You can google "yeast pitching rates" to find lots of information on the subject as well as links to several calculators. Whatever calculator you use, be sure to enter all of the available inputs.

[Richard]

Increasing the time on the stir plate is unlikely to help. Once the yeast have consumed all the nutrients they will not multiply any more, stirred or not. Increasing the size of the starter will help by giving them more to eat, so they will multiply more before running out of fuel.

I make a two-stage yeast starter. I make a 750 ml starter and let it ferment (on a stir plate) for 36 hours, then I cool it down in the refrigerator overnight. The next day I decant most of the liquid and use the slurry to make a 1.5 liter starter. The online calculator I use says that will make nearly twice as many yeast cells as just making a 1.5 liter starter in one stage. It does take two extra days, though.

[Craig]

Thanks for the information