Homebrew Cryogenics

 One of the way to save some money on brewing is to reuse your yeast from batch to batch. With the addition of some simple equipment, anyone can harvest the yeast from previous batches. With only a few additional steps, you can freeze the yeast so you are able to build a "library" of strains that you can use at your discretion.
  This spring I made my first true lager with a Wyeast smack pack that I truly enjoyed and wanted to save this great yeast for another beer in the distant future. I read about this procedure to freeze yeast. So being the experimental homebrewer I wanted to see if I could perform this successfully. I froze my yeast and nine months later decided to revive the yeast.  Success!  It's alive!! alive!
 A couple rules of thumb that I followed and procedure that I performed.
-First, only re-use each original yeast sample 4 times max. Yeast begin to mutate over time, and it may change the characteristics of the strain, thus the characteristics of your beer.
-Secondly, be prepared to be a psycho about cleanliness. If at any time during your harvesting or freezing, a wild spore enters your yeast colony, that colony is ruined.
-Thirdly, I only harvest the yeast from the primary fermenter.
-Fourth, I use a 50/25/25 freezing solution (50% yeast, 25% water, 25% glycerin).
Finally, I don't bother harvesting yeast that was originally in dry form. At a couple of dollars per package, it's just not worth my time and effort.
  Preparation/Equipment
You'll need to do a little preparation in advance. You need to boil and cool a quart of water. Place the cooled water in a covered jar.
You'll also need:
·  A sanitized, 1 quart jar with lid to hold the yeast slurry you've harvested.
·  Something to hold the harvested yeast - I use sanitized White Labs tubes
·  Glycerin for the yeast freezing process (this protects the yeast cells, and prevents them from bursting). You can get this at any large drug store. I bought mine at CVS.
·  A small, sanitized funnel that will fit into the mouth of your yeast tubes.
·  A bowl of sanitizing solution. I use iodophor solution.
Procedure
 After you have racked your beer from the primary into your secondary, attempt to keep a little of the beer in the primary. This will help re-suspend the yeast.
 Then wash your used yeast. washing-yeast-for-reuse
Fill 50% of the yeast tube with the cleansed yeast.
Add an amount of glycerin equal to 25% of the total  tube.
Then fill the remaining 25% with the sterile water and close it up immediately.
It's now a simple matter of shaking the tube up to mix all of the contents, and placing them in the freezer.
 Here's an important note.
Most home freezers are frost free. They have a freeze/thaw cycle that will eventually thaw out your samples. Many brewers that freeze their yeast place their samples in a
 styrofoam cooler, loaded with freezer packs around the yeast samples so the samples don't go through the freeze/thaw cycle.
   Re-using Yeast (prepare 10 days prior to brew day)
  Now the process is one of increasing the population by making yeast starters while maintaining good sanitation throughout.
 -Remove yeast sample from freezer and place in refrigerator to thaw undisturbed for 3days.
 -Make a starter. how-make-yeast-starter
- After 3 days remove yeast from fridge and warm to room temperature.
- Gradually step-up the yeast production to brew day. Start with (2 oz.) of wort in a jar for 2 days.
- Then add one pint and occasionally swirl for 2 days.
- Now move to stir plate if you have one and add another pint of wort. Step it up more in a couple days if you like.
 When the beer is finished, you can repeat the harvest/freeze process up to 4 more times.