So following advice of the last few days’ posts, I mashed at a little higher temperature than usual (152F instead of 148) and with a higher end ratio of 1.8 quarts per pound. My end runnings were 1.017 and my grain bed was rock solid (so I knifed it with my mash paddle as it was draining to get the last half gallon of the wort). 11 gallon batch - the highest efficiency I have ever experienced.
I’m assuming the flow rate for your run off was slower than usual? If so, that is likely the reason your efficiency was improved. If you are willing to spend the time, high efficiency is possible.
Maybe a little slower, but not substantially. It seemed to be the thinner mash that made a difference in how the bed set so solid on the second run after the batch sparge water was added. And I stirred it well after adding the sparge water…but now that I think about it, my neighbor borrowed my mill recently and he took it apart and reset the gap - that was likely part of it, too. I don’t have anything to measure the gap, so I trusted him when he said he set it at 39 thousandths!
New mill setting, higher temp, and looser mash were all factors. Hard to say which was mainly responsible.
Probably a combination of all of the above, so now. To replicate those results consistently … That will be the key!
I don’t know it’d be the mill setting, unless he reset it tighter than you had before, whatever the factory settings were. If it’s a barley crusher, of course most of us know, that those are factory set to .039". But I don’t know if I’d conclude that mashing at 152 versus 148 was what gave you the higher efficiency. Either way, it’s nice to get better than expected efficiency. I always get bummed out when I miss my OG by a couple points. But it’s really not a big deal.
Highly unlikely that flow rate will result in any improvement in efficiency for a batch sparge. Unless, perhaps, if it results in a slightly longer mash.
Crush, temperature and thickness, however, have all been shown to effect mash efficiency. Get it all right and you get reliable mash efficiency because it is always the result of complete conversion. Then, grain weight becomes the only variable between batches.
I know that when I went to 2L/lb my efficiency went up. Personally I like a thinner mash and unless I run out of room I always shoot for 2L/lb, sometimes even a bit more if I miss my strike temp and have to screw around with the temp.