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rtr

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So...I took my first shot at re-using yeast slurry a few weeks back. Things seemed to go fine for the first 2 days, but then the krauesen went and dropped back in before a full 3 days.

I thought, maybe I underpitched. But I decided to give it a little while to do its thing.

On day 10, I took a hydrometer reading. 1.021. OG was 1.046. Well, maybe it's just taking a while.

I went out of town for a few days. Came back on day 14...1.021 again.

So...obviously I've waited a little long on this, but is it possible to pitch a little more yeast at this point? And if it is possible, what are the downsides?

And how do I figure out if I pitched enough yeast slurry in the first place?
 
You should have made a starter.

Check out the yeast pitching calculator on mrmalty.com for all your yeast pitching needs.
 
Re-pitching sounds like your best bet. The down side is more work, but hey that’s homebrewing right?

A couple quick questions: 1) what was the OG of the first batch? 2) What was your aeration procedure for this batch?
 
For the re-pitch to work I think you will need to get it active. Make a starter and pitch that at high krausen.
 
The OG for the original batch, I believe, was about 1.065. I had intended this one to be about the same, but wound up adding a bit too much top-up water at the end.

As for aeration, both times I have poured the cooled wort into the fermentor, put a lid on it, then shook the hell out of it until there was a huge head of foam on top.

Glad it's not too late to repitch...though, that does raise a few questions.

1. Is it bad to re-aerate the partially fermented beer?

2. Do I need to let it wait for another week or two before it's finished?
 
The OG for the original batch, I believe, was about 1.065. I had intended this one to be about the same, but wound up adding a bit too much top-up water at the end.

As for aeration, both times I have poured the cooled wort into the fermentor, put a lid on it, then shook the hell out of it until there was a huge head of foam on top.

Glad it's not too late to repitch...though, that does raise a few questions.

1. Is it bad to re-aerate the partially fermented beer?

2. Do I need to let it wait for another week or two before it's finished?

1. yes very bad

2. maybe if your lucky
 
The reason I ask for the OG of the first batch is because typically you want to step you yeast up from a lower gravity batch to a higher one. If you do that in reverse there’s a good chance your yeast are too depleted from the higher gravity batch. 1.065 is probably a bit higher than ideal to reuse.

If you repitch now DO NOT re aerate and you you’ll just have to wait as long as it takes for the new batch of yeast to finish their sugar dinner.

I had a similar situation with a cream stout last fall. I reused yeast that I probably shouldn’t have and had an under attenuated batch. I simply bought more yeast, repitch and let them do their thing. In the end everything worked out, just on a slightly longer time line, and the beer was great.
 
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