First time using yeast cake.

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Feb 11, 2020
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So this is my first time ever reusing yeast this way. I primarily brew NEIPA. I brewed this past Monday and my yeast starter was not looking good. I had a fermenter with the yeast and leftovers that had been sitting for about a week ( I do closed fermentations and transfers) so I put the wort into that fermenter and holy ****!! The craziest fermentation I’ve ever had. From .065 to .004 in 72 hours. I’m afraid this one might be too dry. Any tips or other experiences like this out there? By the way yeast is 1318 and temps got out of control it was 82 when I checked the second day put it in the basement where it’s like 62 ish and it was still 70 today.
Aside from the temp swings you will probably be just fine. Your beer will finish faster than normal, no biggie. Plenty of brewers do this. Anytime I have reused a yeast cake the fermentation is pretty explosive. An alternative is to toss the cake into mason jars or something to be used later. I like pint jars so I can have at least two jars from each batch to repitch if I want to. No starter needed.
You seldom want to use the entire cake.

I will occasionally use a full cake, but that's only when I'm brewing a very, very large beer (RIS or large Burton Ale) but in those cases, I'll use an entire cake from a very small beer (typically a mild or ordinary bitter). In other words, I'm using a very small beer as a 5gal starter for a substantially larger batch.

Back in Ye Olden Days when I was first learning how to reuse yeast, I started trying to narrow the gap between the first and second beers. I did this with great success (although it stressed the hell out of my temp control). Eventually, I got it into my head that there must be "a rule of ten." That is, if you pitch a beer ten points higher, you'll be okay.

This was incorrect. Terribly incorrect, in fact. Yeast are incredibly stupid. They don't know anything about math, much less our societal convention for base ten arithmetic systems. They are quite good at fermenting and when you pitch a 1.060 beer onto a 1.050 cake, they are jaw-droppingly good at fermenting--unfortunately they're quite bad at fermenting beer in such a circumstance. The result was a vile mixture of fruit cocktail and bacon. It was my only dumper, but perhaps these are prized qualities in a NEIPA? ;)

There are a lot of ways to re-pitch yeast, most are unnecessarily complicated. You certainly can go wrong, but you often won't go wrong by simply scooping out a pint-sized Ball jar worth of trub/yeast and re-pitching it the same day, or following weekend. If you're doing a lager, or a substantially larger ale, use two pint-sized Ball jars.

Also, this may be helpful in understanding how yeast work.

I hope you found this useful.
I've done a couple dumps in a row onto a full cake. Beer came out fine.

In retrospect I would have dumped about half the old cake each time.

From what I gather from other's conversations is that the yeast needs time to "adjust" or "modify" to the fresh wort and build it's colony back up before deciding what it wants to do. An overpitch will ferment out so fast that the yeast is still thinking it's the old style wort before it realized that it's a whole new wort.

when I harvest yeast for later I only do 1/2 pint jars. And only about 1/2 the jar actually makes it into the fermenter. From one cake I get 2-4 jars. I can then select the jar that does the best "sniff test".