A few weeks ago, I suggested that it would be a good idea to check the gravity of the final runnings to help determine the root cause of a low efficiency problem.
Kaiser correctly pointed out that this would not really be a useful check by itself, and suggested that to check for channeling, you could to do a batch sparge after the fly sparge was complete, and then compare the gravities between the final runnings of the fly sparge, and those obtained from the subsequent batch sparge.
Just to see what difference there was, I performed this yesterday.
Normally, I shut off the sparge water when I know there is enough in the sparge to make up the volume to the kettle. For the check, I allowed the sparge water to continue flowing into the mash until I had about an extra gallon. This left the mash loose enough to give it a good stir without introducing extra water which could reduce the batch sparge gravity.
At the end of the fly sparge, I took the gravity of the final runnings 2.25 Brix - 1.00844 S.G. (Actually, I used the refractometer because it's much easier.)
I gave the mash a good stir, and put the kettle onto the boiler.
10 minutes later, I returned to the mash, and gently drew off 1 qt of the mash. (This would have been below the false bottom, and would not be much affected by the stirring.)
I then checked the runnings again. They had dropped to 2.00 Brix - 1.00750 SG. I took several more readings as I drained the mash, and they all stayed at 2.00 Brix.
If I did have a channeling problem, I would have expected to gravity to increase quite substantially after stirring.
All in all, I was pretty pleased with this brew. O.G. was 1.074 from 12.25# grain, and 87% efficiency into the kettle, all in a 5g cooler and not collecting any more wort in the kettle than normally. :rockin:
-a.
Kaiser correctly pointed out that this would not really be a useful check by itself, and suggested that to check for channeling, you could to do a batch sparge after the fly sparge was complete, and then compare the gravities between the final runnings of the fly sparge, and those obtained from the subsequent batch sparge.
Just to see what difference there was, I performed this yesterday.
Normally, I shut off the sparge water when I know there is enough in the sparge to make up the volume to the kettle. For the check, I allowed the sparge water to continue flowing into the mash until I had about an extra gallon. This left the mash loose enough to give it a good stir without introducing extra water which could reduce the batch sparge gravity.
At the end of the fly sparge, I took the gravity of the final runnings 2.25 Brix - 1.00844 S.G. (Actually, I used the refractometer because it's much easier.)
I gave the mash a good stir, and put the kettle onto the boiler.
10 minutes later, I returned to the mash, and gently drew off 1 qt of the mash. (This would have been below the false bottom, and would not be much affected by the stirring.)
I then checked the runnings again. They had dropped to 2.00 Brix - 1.00750 SG. I took several more readings as I drained the mash, and they all stayed at 2.00 Brix.
If I did have a channeling problem, I would have expected to gravity to increase quite substantially after stirring.
All in all, I was pretty pleased with this brew. O.G. was 1.074 from 12.25# grain, and 87% efficiency into the kettle, all in a 5g cooler and not collecting any more wort in the kettle than normally. :rockin:
-a.
