Even though I've only been brewing for a few years, I like to think I'm pretty good at this.
That's what makes nights like this so humbling.
I made an Oktoberfest back in April. It spent about 2 weeks in primary before I transferred it to a keg for lagering, on April 28th. I left the yeast cake in the carboy, and stashed in a dark closet.
3 weeks later, this past Sunday, I brewed up an interesting beer that I thought would go well on top of that lager yeast cake, and I pitched it directly on top of it. I gave it a shot of oxygen, cooled it down into the lower 50s, and threw it in my fermentation chamber.
This was 4 days ago, on Sunday.
After two days without any signs of fermentation, I started to get a bit nervous. I've only made a few lagers, but I usually at least see a couple bubbles from the airlock, or the beginning of a krausen layer on the top. But I wasn't seeing anything at all. I ramped the temp up a few degrees into the mid-50s and waited another day.
Yesterday, I still wasn't seeing any signs of fermentation, so I dropped my hydrometer directly into the carboy just to see if the yeast was working, but working surreptitiously. No such luck - the hydrometer sat right at 1.060, which was exactly what the original gravity was when I pitched four days ago. I ramped up the temp a few more degrees, shook the carboy to try and get some yeast into suspension, and let it sit one more day, until today.
Tonight I came home, and still no signs of fermentation. The hydrometer is still sitting right at 1.060. I pulled a sample, and sure enough, it's still just sugar water.
So - here's where I have to have faith in my sanitation techniques. After four days, without a yeast colony eating the sugars and creating alcohol, it's an environment that's been ripe for bacteria and wild yeast.
I didn't want to write the batch off entirely. But I have to believe that 3 weeks at room temperature killed my lager yeast cake, based on the fact that it doesn't appear to be making beer. Filing that information away as an important safety tip (thanks Egon!), I decided to try and rack the wort off the lager yeast and onto some ale yeast. It just so happens that I have a yeast cake of S-05 ale yeast that I'd used for an IPA recently sitting around, so I racked on top of that.
I tried to leave as much of the lager yeast in the original carboy as possible, and tried to just bring over the wort, but I know I wasn't 100% successful. So I'm trying to ferment this bad boy as close to 60 degrees as I can. That'll be on the low end of the tolerable range of the ale yeast, but won't be significantly out of the range of the lager yeast. The goal here is that if any of the lager yeast did survive, I don't want them reproducing and creating off flavors in this beer.
To be frank, I did several things wrong here. The first was letting the lager cake sit at room temperature for three weeks without feeding it any fresh wort to keep it viable. The second was not having spare lager yeast on hand to pitch on top when I first started to suspect I had a problem two days ago. The third was using a yeast cake in the first place - you bring along whatever extra trub was left over from previous batches, as well as what's usually too much (or in this case, too little) yeast.
But, it's a hobby. If this batch goes kaput, I'm only out about $20, plus the time it took to make it. I can live with that.
Still. I really hope I can salvage this batch. At this point, my primary concerns are that something got into it and it's already too late, or that the lager yeast that got racked over will contribute off flavors.
I'll probably know more in a week or two. Until then, wish me luck.