So today I was brewing a very large Belgian style beer, BIAB style. I had ~17lb of grain.
This is my 5th batch using BIAB. The first two I got 70% efficiency, and the second two I got 60% efficiency.
This time I got a grain mill and ground the grain finer than the previous two times. I even did a small sparge to try and bump up my efficiency, especially because I had more grain.
Everything seemed to be going well. My thermometer was reading mid to high 140's instead of 150 which was my target, but this was near the surface, in the very middle, so I didn't think this was a big deal.
After my small sparge I checked the gravity, it was reading 1.02, I couldn't believe it. I took the gravity a couple more times, stirring between each time, and even check the meter against water.
We decided to continue to sparge the beer, and even mashed it for a little bit longer. By the end we got the gravity up to 1.035, which was 35% efficiency. This is a terrible efficiency, does any one have any idea why it was so low?
The only thing I could think of was the temp, it was cold out, ~5C, so I did keep the burner on low to try and counter this. Any ideas for what I could do next time to improve my efficiency? I am just thinking of converting a cooler to allow me to mash in doors.
Your help is greatly appreciated!