Reusing yeast

Yes, but how well it'll work depends. What was the OG or ABV of the first beer? Yeast are happier in a second batch if the first one is relatively low ABV style (≤ ~5%). How long ago is "the other day"? Has it been kept cold? If it's fresh, kept cool, and from a low ABV beer, it'll work fine. How much to use? See Mr. Malty.

 

I would not recommend reusing this yeast. Because it's been open for some time and the carboy is all headspace, the probability is high that the yeast has become infected. Racking the beer allows air to fill the space and we all know where those evil bacteria live. I have seen krausen residue on the sidewall of a fermentor start growing pellicle in as little as two days after racking.

But reusing yeast is very common and not especially tricky . . . if you do it the same time as racking. Here's a pretty good tutorial.

 

I usually take the extra step while racking and wash the yeast cake before putting it in sanitized jars. I'm doing my 6th saison of the year this weekend from the same smackpack of 3711.

 

I was going to post a similar question. I brewed a single hopped pale ale and want to just repitch on the yeast cake.

The question I have is I didn't use a hop bag. If I am going to re-pitch on yeast cake does that matter? I am going to brew another single hop pale ale.

 

Disregard my post above ^^. After further research I am going to wash and then repitch.

 

You can use an unwashed slurry with good results. Mr Malty says use ~ 1/4-1/2 cup to pitch.

 

Hmmmmm, that sounds a whole lot easier than washing yeast. Can I take slurry and save it to pitch a few days later?

 

I have. As long as it was a relatively bland wort and kept cold . . .

 

Nope. When racking, you immediately boil some water for sterilization purposes, cool then add to yeast cake. Agitate it, getting nice and fluid, put into sanitized jars/containers, do not seal completely, and let them stratify. Save the middle part of that slurry.

 

I wash yeast as sop. I will save usually 4 pint sized jars of yeast, when I use the last jar I'll wash again. I have 7 strains on hand and have never had an issue.