First, I apologize that this is so long. Second, thank you to anyone willing to slog through it and tell me how I screwed up. I expect to dump my last 3 brews, 25 gallons, due to severe under attenuation.
These brews were my 57th, 58th, and 59th batches. All were primarily extract, although two involved a mini-mash with a tiny amount of Munich.
I brewed a pale ale first, with an OG of 1.043. I made a 1-liter starter (1.035–40) with a very fresh pack of 1056 the night before on a stir plate, and pitched the entire starter. FG 1.024, or about 48% attenuation.
Second was a big red ale (Gordon clone attempt), using the amount of slurry called for by the Wyeast calculator. When fermentation had slowed down, I found it very underattenuated, and pitched two different dry yeasts in an attempt to help if finish, to no effect. It had 50% attenuation.
My third batch was a RIS. It was obvious that the 1056 was not attenuating, so instead of using the slurry from the red ale, I double-pitched S-05 dry yeast (2 packs per fermenter, rehydrated before adding). The fermentation looked normal, lasted a normal time, but attenuation was 46%. I added Wyeast yeast nutrient per directions to the red and RIS.
For all, pitched at 65-70F, I kept the fermentation chamber (temperature controlled freezer) at 68F (max), but for the red ale and RIS I increased the temperature to 71 from days 3-5+. All were allowed to remain in the fermenter for 2 weeks. I tried rousting the yeast for the red, but didn’t bother for the RIS.
All this convinces me that the wort had very low fermentability. I have brewed two of the three recipes before with good results. The last time I brewed the same RIS recipe, the attenuation was 86%.
Trying to figure out what went wrong, I made a chart of my latest 20 brews, comparing attenuation, recipe type, and whether extract or all-grain. The lowest 5 attenuated brews were all extract, counting these 3. 4 of the top 5 attenuated brews were all-grain, save only the RIS I mentioned at 86%.
All this led me to the conclusion that the Breiss Golden Light DME I used for most of the fermentable was seriously defective. I know I will never brew with it again. I suspect that it was a bad batch, as I know that many have brewed successfully with it. But I wasted a lot of money, effort, and time using it, and see no other explanation that the Breiss DME had very low fermentability due to errors in production.
I would love to learn that I am overlooking a flaw in my process, though, and am not afraid of criticism. I’m just afraid of bad beer! And I have 25 gallons of it in my beer fridge!