So I've been brewing partial mash batches for a while now, using DeathBrewer's approach except that I mash 6-7 lbs in a cooler rather than a kettle. With this approach I've been consistently hitting 70% efficiency, +/- 1%.
Last weekend I did my first AG batch, a cream ale that used 6 lbs 2-row, 1 lb minute rice and 0.5 lb table sugar. It's a 5-gallon batch, the estimated OG was 1.040 and I mashed for 90 minutes instead of my standard 60 minutes. My measured OG was 1.044, which beersmith calculates as 77% efficiency.
I've never brewed with rice or sugar before. This and the 90 minute boil are the only changes to my process. Grain crushed on the same mill, etc. Do you think the jump is because of the longer mash time, the rice/sugar, or just something random and not worth thinking about? I'm just trying to better understand the cause/effect of my process. Thanks.