I brewed a mini-mash last week with three pounds of grain. Used my Igloo 5 gallon cooler with copper manifold (first time using the manifold) and batch sparged. My efficiency was only 71% so I missed my expected O.G. by a couple of points -no big deal, but I have been trying to figure out what's going on and think I may have found the answer. I'd like to see if you guys think this is a reasonable theory.
First, I think the conversion was good - temp was held between 153 and 155, crush was good, pH was OK, sparge water got the grain bed to 166, iodine test indicated total conversion, wort tasted sweet. I think my inefficiency came during lautering, due to dead space in the MLT.
I had previously tested the dead space using only water, and could drain all but about a half cup before the water level dropped to the slots in the manifold and broke the siphon. However, when draining during the mash and sparge, I noticed that there seemed to be quite a bit more water left at the bottom of the grain bed when the siphon broke. During most of the runoff, I had the outlet end of the tube from the MLT at the bottom of the brew kettle, so it would have been beneath the surface of the liquid in the BK, but I did lift it out a couple of times to check the flow rate, particularly toward the end of the runoff. It now occurs to me that that was probably not a good thing to do. I think what happened is that toward the end of the runoff, the flow through the grain was much slower than during my test without grain, even though I had the ball valve wide open. So when I lifted the tube end out of the wort in the BK, the flow rate wasn't sufficient to keep the tube filled, allowing air to enter the siphon from the BK end, something I hadn't even thought about. So the liquid level after the siphon broke could have been as high as the ball valve, leaving as much as 1.5 to 2 quarts (6 to 8 cups) of liquid over and above what was absorbed in the grain, instead of a half cup. Does this sound like a reasonable theory?
First, I think the conversion was good - temp was held between 153 and 155, crush was good, pH was OK, sparge water got the grain bed to 166, iodine test indicated total conversion, wort tasted sweet. I think my inefficiency came during lautering, due to dead space in the MLT.
I had previously tested the dead space using only water, and could drain all but about a half cup before the water level dropped to the slots in the manifold and broke the siphon. However, when draining during the mash and sparge, I noticed that there seemed to be quite a bit more water left at the bottom of the grain bed when the siphon broke. During most of the runoff, I had the outlet end of the tube from the MLT at the bottom of the brew kettle, so it would have been beneath the surface of the liquid in the BK, but I did lift it out a couple of times to check the flow rate, particularly toward the end of the runoff. It now occurs to me that that was probably not a good thing to do. I think what happened is that toward the end of the runoff, the flow through the grain was much slower than during my test without grain, even though I had the ball valve wide open. So when I lifted the tube end out of the wort in the BK, the flow rate wasn't sufficient to keep the tube filled, allowing air to enter the siphon from the BK end, something I hadn't even thought about. So the liquid level after the siphon broke could have been as high as the ball valve, leaving as much as 1.5 to 2 quarts (6 to 8 cups) of liquid over and above what was absorbed in the grain, instead of a half cup. Does this sound like a reasonable theory?
