Regarding random efficiency jumps...

I'm stumped guys. I have brewed about two dozen all grain batches, and every single time my efficiency is almost exactly 75% with my setup.

And then at random, yesterday my efficiency jumped to 80%. What gives?

My grain was crushed the same as always and I didn't stir it any more or less than usual. I did a few things differently this time but I'm not convinced any of them could have been responsible for the bump in efficiency.

1. I used Maris Otter for the first time (btw, this has to be the best smelling/tasting mash I have ever done).

2. I used reverse osmosis water coupled with mineral additions. I've done this for my last two brews too and they didn't have this efficiency boost.

3. I didn't use gypsum as one of the contributing minerals (ran out).

Other than that I really can't think of anything different whatsoever.

Atmospheric phenomenon?

I think your water may have played a part in it more than you think. Are you adjusting to certain pH levels? I did two batches of the same beer a few months ago. One of them, my pH was right at 5.2, the other was at 5.8. The 5.2 seemed to have converted a bit more than the other. There could have been other factors in there, but I didn't really dig into it too deeply.

I think it's the Maris otter. I consistently get 77-79% efficiency with 2-row based bills and I've made about forty all grain batches. So far I've made 6 Maris Otter batches. I've gotten 92, 94, 71, 65, 64, 69% with Maris otter. I've been avoiding MO because it is unpredictable for me. The size of the grain is larger so it seems to crush more fine because of this. But as you can see I get far below good efficiencies sometime as well.

The one thing that I can think of is that British 2 row malt like Maris Otter has about 5% higher yield that US 2 row (38 pppm vs 36 pppm). If you didn't take this into consideration then without any change in your efficiency, you will achieve a gravity increase of about 5%.

-a.

Interesting ajf. I had been operating under the assumption that US 2 row was 38 ppm instead of 36 ppm as you suggest. Seems like I might have had a higher efficiency this whole time and didn't even know it! Cool!

mighty ... i use this a good bit.

https://www.homebrewtalk.com/wiki/index.php/Malts_Chart

I have observed higher efficiencies when I've used Marris Otter, based on figures supplied / calculated by BTP.