A few weeks ago I brewed my first batch of beer. I used the Zombie Dust clone recipe on here. I used the mill at my LHBS, and did a triple crush. I got about 54% brewhouse efficiency.
The mill at the LHBS looks like it has seen better days, so I elected to purchase my own mill hoping I could improve my efficiency with a better crush. I bought the Monster Mills MM2-Pro SL (the one with helical slotted rollers). I milled my grains with my new mill and brewed my second batch of beer yesterday. I followed the same recipe because I wanted to keep all the variables the same and see if my efficiency improved. The only change I made was to add 0.75 gallons to my starting water volume as I didn't collect the full 5 gallons on my first attempt.
The second time around I did collect a full 5 gallons, but my brewhouse efficiency remains at 54%.
The OG was lower on my second batch - 1.047 vs 1.053. I'm trying to hit 1.062 as called for in the recipe. The weird thing is that my gravity at the end of mashing was higher for the second batch than the first - 1.033 vs 1.023.
I'm starting with RO water and adjusting with gypsum and CaCl to hit the balanced water profile on Brewers Friend. That amounts to 1g of CaCl for both batches, 5.5g gypsum for the second batch, 5g gypsum for the first batch. I'm adjusting pH with 2mL 88% lactic acid, and confirmed my pH during mash was 5.35.
I'm hitting my mash temps, and for the second batch I did a better job of keeping the kettle insulated. Starting mash temp was 153F, and it was still 151F 30 minutes into the mash. I'm stirring the wort for several minutes at mash in, and at 15 minute intervals throughout the mash.
I'm spending several minutes squeezing the bag after the mash is over. For my second batch, I lost 0.75 gallons to grain absorption/evaporation during the mash. With a 12lb grain bill, that amounts to 0.06 gallons per pound of grain.
Given all the steps I've described above, the only thing I can think of that would be contributing to such low efficiency is my grain crush. With the Monster Mill, it came set from the factory at a 0.045" gap. I'm using a pretty beefy low-RPM, high-torque Makita corded drill, and I couldn't get the rollers to turn at that setting. I backed it off to 0.050" and while the drill was working pretty hard, the crush that I got looked better, and a little finer, than the crush I got running my grains through the LHBS mill three times.
What is a typical mill gap for BIAB? I'd be happy if I could hit 70% efficiency, but that's a long way away. I suspect the mill gap for a helical roller is a bit different than a knurled roller, but at least I might be able to get a better idea of what I need to be doing. I don't think I can mill at a lower setting than 0.050" for the first crush, I may need to start there then adjust the mill to a lower setting and crush a second time. I would prefer not to have to mill twice, but it's the only thing I can think of that could be holding back my efficiency.
Here is a picture of the crush on my second batch. All grains were broken into multiple pieces, and there was a good deal of flour in the crush as well. I conditioned the grain prior to crushing.
https://dl.dropboxusercontent.com/u/16976040/2016-09-03 15.08.35.jpg
Any input appreciated, thanks!
The mill at the LHBS looks like it has seen better days, so I elected to purchase my own mill hoping I could improve my efficiency with a better crush. I bought the Monster Mills MM2-Pro SL (the one with helical slotted rollers). I milled my grains with my new mill and brewed my second batch of beer yesterday. I followed the same recipe because I wanted to keep all the variables the same and see if my efficiency improved. The only change I made was to add 0.75 gallons to my starting water volume as I didn't collect the full 5 gallons on my first attempt.
The second time around I did collect a full 5 gallons, but my brewhouse efficiency remains at 54%.
The OG was lower on my second batch - 1.047 vs 1.053. I'm trying to hit 1.062 as called for in the recipe. The weird thing is that my gravity at the end of mashing was higher for the second batch than the first - 1.033 vs 1.023.
I'm starting with RO water and adjusting with gypsum and CaCl to hit the balanced water profile on Brewers Friend. That amounts to 1g of CaCl for both batches, 5.5g gypsum for the second batch, 5g gypsum for the first batch. I'm adjusting pH with 2mL 88% lactic acid, and confirmed my pH during mash was 5.35.
I'm hitting my mash temps, and for the second batch I did a better job of keeping the kettle insulated. Starting mash temp was 153F, and it was still 151F 30 minutes into the mash. I'm stirring the wort for several minutes at mash in, and at 15 minute intervals throughout the mash.
I'm spending several minutes squeezing the bag after the mash is over. For my second batch, I lost 0.75 gallons to grain absorption/evaporation during the mash. With a 12lb grain bill, that amounts to 0.06 gallons per pound of grain.
Given all the steps I've described above, the only thing I can think of that would be contributing to such low efficiency is my grain crush. With the Monster Mill, it came set from the factory at a 0.045" gap. I'm using a pretty beefy low-RPM, high-torque Makita corded drill, and I couldn't get the rollers to turn at that setting. I backed it off to 0.050" and while the drill was working pretty hard, the crush that I got looked better, and a little finer, than the crush I got running my grains through the LHBS mill three times.
What is a typical mill gap for BIAB? I'd be happy if I could hit 70% efficiency, but that's a long way away. I suspect the mill gap for a helical roller is a bit different than a knurled roller, but at least I might be able to get a better idea of what I need to be doing. I don't think I can mill at a lower setting than 0.050" for the first crush, I may need to start there then adjust the mill to a lower setting and crush a second time. I would prefer not to have to mill twice, but it's the only thing I can think of that could be holding back my efficiency.
Here is a picture of the crush on my second batch. All grains were broken into multiple pieces, and there was a good deal of flour in the crush as well. I conditioned the grain prior to crushing.
https://dl.dropboxusercontent.com/u/16976040/2016-09-03 15.08.35.jpg
Any input appreciated, thanks!