You don't have to keep buying new vials and packets of yeast from the homebrew store! You can re-use your yeast pretty much as often as you'd like if you follow proper harvesting and washing techniques. In this video, Chad gives you a quick overview of how it's done.
Here's the steps (a for kegging, b for bottling):
1a. If you're kegging your homebrew, siphon the sanitizer from the keg to the bottling bucket (this sanitizes the siphon which you'll need for Step 2a). Place 5-7 pint sized mason jars in the sanitizer solution. Place the jars full of sanitizer on a towel. Place the lids in a container of sanitizer.
1b. If you're bottling your homebrew, fill your bottling bucket with sanitizer and sanitize the bottles in that solution. Also, sanitize 5-7 pint sized mason jars and lids in the solution. Place the jars full of sanitizer on a towel. Place the lids in a container of sanitizer.
2a. Rack your homebrew from the fermenting bucket or carboy to the keg.
2b. Empty and quickly rinse the bottling bucket. Siphon the homebrew from the fermenting bucket to the bottling bucket. Complete the bottling process.
3. When kegging or bottling is complete, boil a half gallon of tap water at a rolling boil for 15 minutes. Allow to cool to room temperature. NOTE: when pot cools down to about 150 degrees you can put it in the fridge or freezer to speed up the cooling process (especially in the summer).
4. When water has reached (approximate) room temperature, pour it into the fermenting bucket or carboy (whichever contains the yeast cake and trub). Agitate the mixture for a minute or until it's homogenized.
5. Pour the yeast "pudding" into the bottling bucket. Spray the spigot of the bottling bucket with sanitizer.
6. Fill four mason jars with the yeast/water mixture, cover. NOTE: the mason jars should have been full with sanitizer up until this point, and there should still be 1-3 unusued jars still full of sanitizer.
7. Place the mason jars in the refrigerator. Wait 30-60 minutes for the yeast and trub to separate. The jars will look like beer parfaits with two or three different, distinct colors and textures. The yeast is the thin, lightest layer on the top.
8. Carefully pour the yeast from the top of each jar into an empty mason jar. You should be able to get 2-4 jars into one empty jar.
9. Label the jar and place in the fridge. This is your harvested and washed yeast. You can use this to brew within the next six months. Be sure to make a starter for your next brew, though. Yeast over six months old may be unreliable depending on the strain and the gravity/desired ABV of the brew.
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