« on: October 05, 2013, 10:06:57 AM »
My first three attempts at Batch Sparging have resulted in poor extract efficiency: 64, 67, and 56% in 12 gal, 6 gal, and 12 gal batches, respectively. The first and third attempts were with a different mash tun (72 qt Coleman Extreme cooler) than the 6 gal batch (Gatorade 10 gal circular).
I have not done anything differently with my crush size (Barley Crusher) since my fly sparging days. Mash temperatures have been hit perfectly (152 F), each with volumes of ~ 1.3 qts/lb, and mashes are all held for 1 hr.
At the end of the mash, I slowly open the valve to set the bed, I recirculate until clear, and then crank wide open to drain. I have calculated that based on where my Bazooka T is connected, I have about 1 gal of deadspace (with grain/solids in there, obviously that volume is lessened, but I would still think that 1/2 gal of wort is trapped in the cooler after each run-off). After Run-off 1, I add essentially 1 gal more water than what I need to collect (to account for the deadspace) of near boiling water (200- 205 F) to raise the bed to 165-8, stir and wait for 30 mins, then repeat the slow drain, recirc and collect.
My first run-off on the last batch collected 7 gals (on 28 pounds) for the first run-off. I added 6.5 gals of water, stirred, waited, etc. Collected another 5.5 gals for my target of 12.5 gals in the kettle, and only got 56%.
I feel like the process is sound, but if I could guess what is wrong, I think it has to do with something in the second run-off, either the deadspace under the Bazooka T, or how much water is being added to collect the second run-off. The second run with a 6 gal batch anf a different mash tun was higher (67%) but still not great. The amount of deadspace in that cooler is much less.
I like the concept of batch sparging and want to get it right. There has not been any issues with the taste of the beer (as one could expect), and in the grand scheme of things, I could just add another pound of malt to hit higher gravities. However, I would like to maximize the efficiency of my system to at least 75% and be consistent with it. Any thoughts would be appreciated.