HI everyone-
Just finished a hellish brew day trying to make a clone of Kate the Great. Disaster, but that is another story.
I was trying to figure out how to calculate the pre boil gravity with BIAB, and I am not sure I am doing it right. My understanding was that BIAB efficiency was essentially just lautering efficiency, and that conversion of starch to sugars was pretty easy to do to get close to 95-100% conversion efficiency. Is this right?
For instance, the Kate The Great recipe counts out to 1034 points by my reckoning for a 7 gallon batch. With 2.5 gallons boiled off and 2.35 gal retained by the 29.4 lbs of grain, I needed to start with 11.85 gallons.
If grain conversion efficiency is close to 100%, then shouldn't expected preboil gravity just be 1034/11.85, or 1.087?
If that is correct, then I must be doing something very wrong. I didn't bother with an iodine test as the beer is pretty much black anyway, but I have done this in the past and it looked like I had full conversion. Today's pre boil gravity was 1.070 (about 64% efficiency per beersmith), and looking back at all of my previous records, the pre boil gravity usually correlates to about what beersmith calculates if you choose 80% efficiency. I crush fine and recirculate with a RIMS tube, and stir every 15 minutes, so I would HOPE that I would be getting pretty decent conversion.
So does this mean, then, that I am only converting usually 80% of the starch present into sugar, and in today's batch, only 64%??? I crush fine and recirculate with a RIMS tube, and stir every 15 minutes, so I would HOPE that I would be getting pretty decent conversion. Wouldn't the 20% of unconverted starch show up as positive on the iodine test?
Just finished a hellish brew day trying to make a clone of Kate the Great. Disaster, but that is another story.
I was trying to figure out how to calculate the pre boil gravity with BIAB, and I am not sure I am doing it right. My understanding was that BIAB efficiency was essentially just lautering efficiency, and that conversion of starch to sugars was pretty easy to do to get close to 95-100% conversion efficiency. Is this right?
For instance, the Kate The Great recipe counts out to 1034 points by my reckoning for a 7 gallon batch. With 2.5 gallons boiled off and 2.35 gal retained by the 29.4 lbs of grain, I needed to start with 11.85 gallons.
If grain conversion efficiency is close to 100%, then shouldn't expected preboil gravity just be 1034/11.85, or 1.087?
If that is correct, then I must be doing something very wrong. I didn't bother with an iodine test as the beer is pretty much black anyway, but I have done this in the past and it looked like I had full conversion. Today's pre boil gravity was 1.070 (about 64% efficiency per beersmith), and looking back at all of my previous records, the pre boil gravity usually correlates to about what beersmith calculates if you choose 80% efficiency. I crush fine and recirculate with a RIMS tube, and stir every 15 minutes, so I would HOPE that I would be getting pretty decent conversion.
So does this mean, then, that I am only converting usually 80% of the starch present into sugar, and in today's batch, only 64%??? I crush fine and recirculate with a RIMS tube, and stir every 15 minutes, so I would HOPE that I would be getting pretty decent conversion. Wouldn't the 20% of unconverted starch show up as positive on the iodine test?