For some reason, I thought we’d already written a post on this very topic, but to my surprise, I couldn’t find it. So, I’ve decided to write down a very brief tutorial on the subject of making a yeast starter—or at least how I do it.

For those of us who brew, we’ve often seen yeast packs or recipes that recommend making a yeast starter for beers that are over 1.070 degrees gravity (i.e., the beer has the potential to reach the ABV level of roughly 9.2%, assuming full fermentation).  The reasons behind this are many.  For one, a higher gravity creates a more hostile environment for lower levels of yeast.  Secondly, the small level of yeast simply can’t uptake sugar and multiply fast enough to keep up with levels.  They can literally explode.  Furthermore, higher sugars mean higher viscosity, which means lower oxygen uptake.  Because of this, the smaller amount of yeast has more trouble feeding off the lower levels of dissolved oxygen.  Additionally, as the ABV levels rise, the yeast is in an even more hostile environment.  For all these reasons (and more), you’ll see that starters are advisable for higher gravity beers.

Think of it this way: say you had to weed your garden in very hot and hostile temps.  Imagine that the garden is huge and there are a ton of weeds to cover.  Would you prefer to do this job on your own?  In this case, you might not ever finish or you might even collapse from exhaustion.  Or would you rather have a whole army that could more quickly, thoroughly, and easily knock out the task?  I know which I’d choose.  Apply the same line of thought to yeast; get an army to do the job of a few soldiers.  You get the point.  But how do you make a starter?

The first thing you need is a vessel that works well for making a starter.  Your five or six gallon fermenter is overkill, and it may be too rich an oxygen setting for your small army.  I always use a gallon fermenter, which I also use for experimentation.

Following normal pitching procedures is probably the best way to approach the starter.  What I mean is, take the liquid yeast (re-hydrate first if it’s powder) and give it the normal 3-6 hours innoculation period.  From there, you need to maintain normal sanitation practices.  Clean the one gallon fermenter with the solution you use (chlorine and iodine solution in my case).  When you are getting ready to pitch the yeast, boil one quart of water a put in 3/4 a cup of pilsen malt.  (I suggest pilsen malt because it ferments cleanly and relatively neutrally.  You can do something else if you wish but there is no guarantee against off flavors from other sugars and subsequent yeast production.)  Boil for for about 15 min.  Cool the wort to proper pitching temps (around 70º or so), pitch it in, and give it a good shake.

Note:  Avoid putting anything in the wort to cool it.  Ice in particular is a bad idea.  An ice bath outside the pan is fine.  Just remember to make sure the water from the outside doesn’t get into the wort when you pour it.

Now you have a starter.  Making this the day before brewing ought to be just fine.  I always wait until my yeast settles, dump all but a little bit of the liquid out, shake the yeast with the small remaining liquid and pitch into the larger wort.  For really big beers, I’ve fed the yeast for up to a week.  The more the merrier.

Sanitation Note: Remember that the airlock you use can collect bacteria, so clean it up before taking it off.  Some suggest isopropyl alcohol and a lighter to get sterilization.  I’ve always found a good cheap vodka to work just as well.  Q-tips are just about perfect for a job like this.