Preparing a yeast starter from a culture

Step one to propagate yeast from a slant culture is to allow the slant to come to room temperature. Then make some wort to grow it in. 

Get out a couple of test tubes, foil to cover the containers, inoculation loop and a lighter. 

In a flask, measure out 58 grams of dry malt extract, for 500 ml of water.  This will make wort that it about 1.040.Carefully bring the wort to a boil to sterilize it. Allow it to cool. 

 Sterilize the test tubes and foil covers.

 Flame the inoculation loop, scrape some of the yeast off of the slant of growth media and put it in about 10 ml of the sterile wort. Put the test tubes somewhere around 75 F, and wait for signs of growth.

Once active growth is present (it will foam up when swirled) double the volume in steps, up to about a liter of active culture.  I put it on a stir plate once it's more than a test tube's volume to provide more oxygen for the yeast's growth.

 To verify the number of yeast cells present draw up 10 ml of the stirred culture and dilute up to 50 ml with water.

Put a drop on a hemocytometer. A hemocytometer is a special microscope slide with a counting chamber marked off in a grid. Each square is a known volume, so by counting the number of cells in a sampling of squares, accounting for the dilution and the total volume of the starter culture, the number of yeast cells can be calculated. In this case, my starter had 146 billion yeast cells.  The recommended pitching rate for a 5 gallon batch of 1.060 original gravity wort works out to 233 billion, so I'm a bit light on the yeast.