[quote="jamilz"][quote="DannyW"]I'm also seeing conflicting information on how fast to run the stirrer. Some say make a vortex, others say just enough to keep the yeast in suspension. What is the correct answer? If nobody knows, this is starting to sound like a great experiment![/quote]
You want surface exchange to be able to pick up the O2. Increase speed until you get a vortex going.[/quote]
The links below show that stirred starters will definitally outdo a non-stirred starter by many fold. "Continuous agitation/aeration can yield as high as a 10- to 15-fold increase in yeast cell number." This article states that 8-12ppm of O2 should be present in the starter at a temp of 77F. Having the correct temp is also a really important detail. He also recomments piching while the yeast are rapidly reproducing. This is actually a really good article.
Yeast Propagation and Maintenance: Principles and Practices
http://www.maltosefalcons.com/tech/MB_R ... turing.php
Graham Sanders says basically the same thing as jamil about dry yeast, their cell walls are weak and unable to correctly operate.
http://oz.craftbrewer.org/Library/Metho ... east.shtml
How to make your own stirplate.
http://brewiki.org/StirPlate
BTW, a good trick to use to prevent your stirbar from dumping into your wort is to use a strong (yes strong) magnet that you can hold to either (1) in your hands and place the stirbar at the edge of the flask or (2) run the stirbar up and out of the flask b4 pouring. Dont pour from where the stirbar ran out since the magnet would touch the top of the flask and is no longer sanitary.
