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Yeast Starter:
A yeast starter is useful if you are making a strong 5 gallon batch of beer or a 10 gallon batch of beer that might need more yeast cells than what comes from the original package.  Yeast starters are also useful when culturing yeast from a bottle.  The process is basically the same either way, just keep in mind that you want to begin the starter 1 - 5 days before brewing the beer that you will be pitching the yeast into.  This will give your tiny yeast army time to prepare for the feast. 

The most important part of making a yeast starter is to be sure you have everything sanitized that will be coming into contact with your wort.  This is particularly important if you are going to be culturing from a bottle.  The yeast in the bottle will be weak and you will not have many cells, so you don't want anything in the bottle growing faster than your yeast.  For equipment you will want to have a large enough flask or mason jar that fits the needs for your starter.  A stir plate is good to have but is not needed to make a good starter.  The steps below should be used as a guide to making a yeast starter.

  1. Begin by sanitizing a flask or mason jar to be used as a fermentation vessel.  Be sure to also sanitize anything that will be coming into contact with your cooled wort.
  2. Make a mixture of about 0.25 - 0.5 cups of dry malt extract to 1 quart of water.  You want the final gravity of the wort to be about 1.030 so that the yeast are not stressed. 
  3. Bring the mixture to a boil for at least 20 minutes to pasteurize the mixture.
  4. Cool the wort to pitching temperature, around 70 degrees Fahrenheit using an ice bath.
  5. Now transfer the cooled wort into the flask or mason jar and cover with a sanitized piece of aluminum foil.           Note: if you have a gas stove you can heat the wort while in a flask (not a mason jar), leaving less chance of contamination.
  6. Now transfer the yeast from the package or bottle into the flask and reseal with the aluminum foil or a stopper and airlock.  If transferring from the package be sure that the package is sanitized before transferring.  If transferring from a bottle make sure that about an inch of beer is left in the bottle to swirl around and get all the stubborn yeast off the bottom of the bottle.  Before transferring from the bottle be sure to flame the opening for less chance of contamination.  At this point you could also use some of the yeast to streak some plates or slants for yeast culturing.
  7. If you have a stir plate you can drop a sanitized stir bar in to the wort and use the stir plate to keep the yeast suspended.  If not just make sure to swirl the mixture around whenever you get a chance.  You should start to notice activity or yeast cake forming within a few days.
  8. Once ready you can either pitch directly into a waiting batch of beer, or cool the mixture so that the yeast will settle to the bottom, at which point you can then pour off the top liquid and only pitch the yeast into the beer.  Be sure to let the yeast warm up to room temperature if you will be cooling before hand.
Keep in mind that your starter could be infected, so if it looks or smells funny don't pitch it.  Chances are if you have taken proper steps to keep everything sanitized you will not have a problem, but as you know from brewing beer some times you get a bad batch.

Bottle Culturing:
Culturing yeast from a bottle is a technique used to culture brands of yeast that are not commercially available.  Keep in mind that most beers can not be bottle cultured, because they either have no yeast (filtered beers) or the yeast are dead due to pasteurization or high alcohol content.  Even if you find a beer that has been bottle conditioned, which you can tell by the yeast in the bottom of the bottle, chances are the yeast they used to bottle condition is not the same yeast used during the fermentation process.  The most popular beers used to bottle culture yeast is the Rogue Brewing Company's beer.  I believe Rogue actually mentions on the bottle if the desired 'pacman' yeast was used for fermenting their beers.  They use a different strain of yeast for the Lagers than they do for the Ales.  The steps for culturing yeast from a bottle start more or less the same way as making a starter.  This is done to wake up the yeast and get them to multiply by feeding them.  The only addition to the above steps are to be more cautious of contamination.  Yeast from a bottled condition beer are very weak.  In addition to the technique above you could also use lower gravity wort around 1.020 to do 'step ups'.  Doing a step up has the advantage of not stressing the yeast out.  Basically you perform the procedure above using a lower gravity wort as mentioned then after a few days add more wort at a slightly higher gravity.  This is done a few times until the desired results are achieved. 

Streaking/Slanting/Harvesting :

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