I get questions at the store all the time about making a yeast starter. Here is a brief question and answer to help guide you.
Do I need to make a yeast starter?
No, you do not need to make a starter, but it does help. There are circumstances when making a yeast starter is highly recommended. Most liquid yeast packs contain about 100 billion cells when fresh. Dry yeast packs usually have about 150 billions cells. But as these yeast packs age the cell count will degrade. So if you have a older or even an expired yeast, make a yeast starter. If you are doing a high gravity beer, you want a higher cell count. Also if you are making a lager, you want a higher cell count. Making a yeast starter will increase yeast cell count and give your high gravity or lager beer a better fermentation.
Do I need to use a stir plate?
No, you don't need to use a stir plate, but it helps. Using a stir plate keeps the yeast in suspension, so it doesn't settle in the bottom, making it easier to pitch. It also helps keep the yeast active. And pitching an active yeast into our wort is ideal. It will reduce lag time from days to hours.
If I'm making a high gravity beer, should I also use a high gravity starter?
It may surprise you to know that the answer is no. High gravity wort can actually stress the yeast somewhat. Ideally our starter gravity should be between 1.035 and 1.040.
Should I add hops to my yeast starter?
It's not necessary to add hops. On the other hand, there is no reason you can't add hops. If you decide to add some hops, keep the bittering down to about 25-30 IBU's.
When should I make a yeast starter?
You want your yeast starter to be still active when you pitch it into your brew. Since the yeast will consume the sugars in the starter within a day or two, make your yeast starter a day or two before brew day.
I made my starter, but I didn't see any activity in the airlock. Did it fail?
Maybe, but probably not. It's quite possible your yeast consumed all the sugar overnight. If you want to be sure, take a gravity reading with your hydrometer.
How do I make a yeast starter?
Basically you are making a miniature beer. Add about 1/2 cup of Dry Malt Extract (DME) to 1.5 quarts of water. Boil it for ten minutes. Cool it down to fermentation temperature appropriate for the yeast strain (generally 70 degrees for ales, 52 degrees for lager), pitch the yeast and cap it with an airlock. It is not necessary to match the wort composition of the yeast starter to that of the beer. You can just use a standard light malt extract. If you are doing a really light beer like a Pilsner, use Pilsner malt extract.
You can view a YouTube video from the American Homebrewers Association showing how to make a yeast starter here.