Had my first bad brewing experience yesterday.

[Tpost704]

Yesterday I brewed my 7th batch of beer and it did not go well. I attempted to brew Yooper's Oatmeal Stout via the BIAB method. I crushed the grains to .030 and mashed for about 1 hour and 15 min. at 156 in 4.5 gallons of water in an insulated 15 gallon kettle. I added 1.4g of gypsum, 1.4g of calcium chloride, and 4.5g of baking soda to get the mash ph to 5.5 (Used RO water). The mash temp did drop to about 150 by the end of the mash. I dunk sparged in 3.5 gallons of 168 degree water for about 10 min. When I combined the sparge and mash water together, I ended up with about 7.25 gallons of total volume. I took a refractometer reading and it read 5.75 brix (1.0227 SG)! From my calculations, this was around 40% efficiency! I was taken back by this as my last BIAB batch was around 80% efficiency. I continued with the boil and finished with a SG of 1.035. It is safe to say that I totally missed the mark on this mash. With my head hung low I cooled the wort and pitched my yeast starter which took off in just a couple hours. I placed it in my chest freezer fermentation chamber and set to 65 degrees. Come to find out a few hours later that my fermentation is cooking along at 70 degrees and my chest freezer has failed me. It will turn on and run, but does not produce any cooling power. In a last act of desperation, I wrapped my carboy in a wet t shirt and placed a fan next to it to hopefully keep fermentation below 70 degrees. My pride is a little hurt on this one as I have never had a brew go this poorly before.

Just trying to figure out why the mash efficiency was so poor. I think it may have to do with how tightly the grains were compacted together in the bag. I mixed the grains when I added them to the strike water to eliminate dough balls, but I feel that 11lbs of grain in a 5 gallon mesh bag kept the grain packed pretty tightly together. This, in combination with my wide kettle probably did not let enough water get to the grains and extract the fermentable sugars. I am thinking if I get a much larger BIAB bag, that the water can flow more freely around the grains. Not sure if this is it or not, but its a though. Anyway, thanks for taking the time to read and feel free to chime in with any input.

 

[beerlover77]

I find my refractometer always reads low when making beer and I think that it is because it isn't pure sucrose in the liquid. Using a hydrometer at the proper temps gets me much more accuracy

 

[Yooper]

The grains should be very loose in the bag- almost like you aren't using a bag. You want to grains to be thoroughly wetted and in contact with the water to ensure conversion. Did you stir often? That could have helped if the grains were packed in tightly. Sometimes you may want to use more bags, or get a larger bag. I have a huge bag that I use to line my MLT.

 

[Tpost704]

I stirred during dough in but left it alone the rest of the mash. I definitely should have stirred throughout the mash.

 

[Lefou]

I find my refractometer always reads low when making beer and I think that it is because it isn't pure sucrose in the liquid. Using a hydrometer at the proper temps gets me much more accuracy

This is why multiple items are good for measurement.
I have two or three thermometers of different styles. Refractometers and triple scale hydrometers are some handy tools, plus they're relatively cheap.

On another note, I typically calculate my water-to-grain ratio for a thinner mash toward the higher end to account for grain absorption and the boil off of water, then adjust sparge water accordingly.