Yeast

Beer can be divided into two basic types: Beer made with Top fermenting yeast, and beer made with bottom fermenting yeast. Or, Ales and Lagers

Ales were the first beers made. Ale yeasts ferment at warmer temperatures, usually around 40-50 F. At that temperature, the yeasts contribute some flavors to the beer, usually a fruity taste.

Lager yeasts were mastered in Germany, and ferment at 32-38 F. These yeasts ferment out clean, contributing little flavor to the finished beer.

Generally, you can use ale yeasts in Lager recipes, and vice versa, but you will get some flavor differences.

You can also ferment Lager yeast at ale temperatures. That's what Anchor Steam beer does. Back during the Gold Rush, people from around the world flocked to California to make their fortune. Brewers brought their lager yeast and set up breweries. But they couldn't cool the fermenters, so they used open, shallow trays. This procedure created America's only indigenous beer style, California Common.

Today, you can purchase yeast in bags (or smack packs) or in little test tubes. to use the smack packs, you have to burst a smaller bag inside the bag a day or two in advance. The test tubes just brought just have to be brought to room temperature to be pitched.

It's still possible to get dry brewers yeast. But normally that only comes in kits.