WET AND WONDERFUL, LIQUID YEAST
   
 
Each of these yeasts comes in a foil packet inside which is a separate smaller packet containing the yeast starter solution, in other words a small amount of malt extract. This inner packet is surrounded by the liquid yeast. Four or five days before you are ready to brew, follow the directions on the packet, you press the foil pack to break and release the starter solution into the liquid yeast. You then leave the packet lying flat in a warmish place for one to three days. In that time, the yeast will start to multiply in the malt extract solution just as it would in a real wort. The carbon dioxide it gives off makes the packet swell and that’s when you know the yeast is ready for the next stage. You can use it just as it is, pitching it into your wort just as you would do with a dried yeast but you are best to go through another stage first.
 
Because there isn’t enough yeast in the packet at that stage to start off a full fermentation quickly enough to be safe, the best thing to do is culture it up until there is. That’s easy enough. You must make up a starter solution by adding a dessertspoonful of malt extract to 250ml of water, bringing it to the boil then cooling it rapidly down to 28C.  This is easily done by immersing the pot in which you boiled the solution in cold water, making sure you don’t get any of the water into your solution.
 
Now take a cleaned and carefully sanitized 750ml bottle and pour the starter solution into that. Next you must cut the yeast packet open and pour its contents into the bottle, taking care not to allow contact with unclean surfaces. Stop the bottle either with a rubber cork and airlock (sanitized of course), or some cotton wool, give the whole thing a good shake then leave it somewhere warm to go to work. In two or three days (even less if the yeast is fresh), there should be strong signs of activity and the yeast is ready to be pitched into your fermenter.
 
The normal temperature for ale ranges from 16 to 24 degrees C. A few strains ferment well down to 13 degrees C but 20 degrees C is about average. Lager strains normally work between 0 to 16 degrees C but performs best from 10 to 12 degree C for primary fermentation with a slow reduction to  0 degrees C during secondary fermentation. Fluctuations in temperature such as cooling and warming from day to night can adversely affect yeast performance. Each yeast strain ferments different sugars to varying degrees, resulting in higher or lower final gravities which will affect the residual sweetness and body. Some yeasts are also better than others at setting  out and leaving the beer clear.

 

 
       RE-USING LIQUID YEAST
 
There are many ways to reuse yeast, some brewers use techniques involving slants & microscopes, which theoretically would allow reusing the yeast infinitely. The method I have used successfully is to remove half a litre of vigorously fermenting wort two to three days into the fermentation,(there is lots of fresh yeast in it) into a plastic 1.25litre soft drink bottle. Seal & allow to sit at room temperature for a few hours then transfer to the fridge.
 
When you want to reuse the yeast, remove from the fridge a couple of days before  intended use and allow to sit a room temperature for 12 hours. Check to see if fermentation has commenced (pressure in the bottle).    If not, add a solution of one tablespoon of malt extract or sugar mixed in some boiling water and then allowed to cool. Pour this into the bottle a shake vigorously & ensure strong fermentation has commenced before making your next brew.
 
I have reused yeast which has been stored up to 3 months, but a few weeks are probably safer.With each generation, more risk of infection or problems with yeast are likely to occur so this is why a figure of 4 to 5 times is generally quoted as a maximum of reusing yeast unless laboratory techniques are used.
Many people like to make a number of cultures from the packet or from the first brew.

 
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