I have started to reuse yeast from finished brews. It is so easy and of course its free.
The best thing about it is that I always have yeast available when I decide to start a brew.
There is nothing more frustrating then being excited when somebody give you surplus of produce but then you realize that you have no yeast. I have used bread yeast when I was stuck, which worked fine!
Now you don't need to wash the yeast, but it is helpful, if you don't want to pass on flavours from the previous brew, although this can be a benefit.
If you don't wish to wash it just use a few cups of wort from the previous brew.
Or you can just top up the uncleaned demi-john or bucket with your new brew leaving the original wort at the bottom. This is ideal if putting on a similar brew.
How to wash brew yeast:
Add a few litres of water to the wort and let this settle for twenty mins.
Then pour off the water/fluid into a clean jar, leaving behind the sediment.
Leave the jar in the fridge for a week or until you need it.
Then pour off the excess fluid and use the sediment at the bottom as the yeast.
There will be enough for several batches.
It will keep for a few months in the fridge. I have frozen some but have yet to try them.
I have 6 gallons of rhubarb wine on, one gallon of raspberry beer and in the next few days as the elderflower start to open I will be starting elderflower wine.
Our home-brew larder is starting to empty out as we have finished off the ginger beer, larger and yummy nettle beer. That leaves us stout and ale!
That will be a lot of bottles for cleaning this week!!
What are you brewing at the moment?