If you have studied beer for anytime at all, or if you live in a reasonably educated and modern part of the world, then you know what yeast is and why it is important to beer. This is not a post about what yeast is or which of the many strains are best for this purpose or that, rather it is about how many of those little guys you need and how to get them.

One of the easiest things that you can do as a home brewer to improve your beer is to provide the correct amount of yeast to the sweet wort. The correct amount a yeast is a widely debated topic and is dependant on many factors such as volume of sweet wort, the amount of available sugar in the wort, how “stressed” you want the yeast to be for ester production, etc.  A good resource for information on this topic is Mr. Malty, and they even have a handy Yeast Calculator available at the website. However, all this being said, a standard rule of thumb is that you want active fermentation within 12 hrs. The reason being is that yeast changes it’s environment from aerobic to anaerobic during the process of fermentation which makes the environment (the beer) un-inhabitable for all the other little microbes. This ability to change the environment and survive the switch is unique to yeast (as far as I know) and is the major contributing factor as to why beer was the safe drink of choice for thousands of  years.

So how do I get enough yeasties to start the party in less than 12 hrs? There are two ways: you can simply buy more yeast or you can “make” more yeast.  In my opinion, the making more yeast approach at this scale of production is highly preferable. It is significantly cheaper, provides you with greater flexibility in yeast selection (you can “re-purpose” the yeast in the bottom of your favorite hefe for instance), and yeast from a starter is much more active than that out of the vial.

Making a yeast starter is much the same as making beer except the emphasis is on making healthy viable yeast instead of great tasting beer. Your starter should be similar in food source and strength to the intended use. So, if you are making a regular beer, use maltose as the food source. If you are going to be adding large amounts of other fermentables then add a proportionate amount to the starter. This will allow the yeast to become accustomed to eating those types of sugars. Do not worry about adding non-fermentable components of the final recipe, like hops or cinnamon for instance, because the yeast will not really care if it is there. A good recipe to follow for a regular beer is 1 gram of DME per 10 ml of water, so for a 2L starter use 200 g of DME. This should give you close to a 1.040 OG starter.

Our favorite tool for the job is a stir plate because it increases the yeast yield per quantity of starter medium used. Above and below are pictures of our stir plate made from a cigar box, a couple computer hard drive fans and some rare earth magnets.  Check back soon for a step by step build of your very own stir plate.