Yeast Basics: Making a Starter

Making a yeast starter is a necessary skill for someone who wants to brew beer. A yeast starter takes either a small quantity of yeast and grows it to the volume needed to ferment a batch of beer or takes a culture of yeast that is not healthy enough to brew a batch of beer and produces new cells that will be able to ferment the beer, or both.

In order to create a yeast starter you will need a few basic things...

1. Dry Malt Extract
2. A sterile vessel 
3. Tin Foil
4. A stir plate (not essential)
5. Yeast
6. A sterile toothpick of inoculation loop
7. Scale

Directions...

1. The first step is to make a wort that is about 1.030 gravity. This is easy to do using Dry Malt Extract, simply add 0.75 oz of Dry Malt Extract for every cup of water. 
2.  Boil the wort 10 minutes to sanitize it
3. Sanitize the inoculation loop and whatever you will be growing the yeast in
4. Add the wort to the vessel and place tinfoil over the top, allow the wort to cool to 80 F
5. Add the yeast, using sterile practices, to the wort (you will only need a very small amount of yeast, a few colonies will do)
1. If you have a packet from Wyeast or a tube from White Labs you can add the whole tube

A few notes:
The size of your starter is important. If you are starting yeast from a plate then you need to start them in a small volume of starter (100 mL) before you step them up to something larger like 500 mL or a liter. If you are trying to boost your cell count from a packet of Wyeast or a vial of white labs you are going to want to go big, like 1.5 L. Otherwise the yeast are not going to be able to do much dividing.
You can either pitch the entire starter or you can do what I do, which is place it in the fridge the night before to help the yeast floculate. Then you can decant the fluid and add only the yeast to your wort.