DarwinsMonkey
Member
- Joined
- Oct 22, 2012
- Messages
- 8
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Hey guys,
First things first, love the HBT forums, you guys have answered so many of my questions over that past 6 months. That being said, I have a major annoyance I was hoping someone could help me out with. I can never accurately calculate my post boil gravity, no matter how accurately I measure my preboil. Here's yesterday's batch as an example:
Preboil was at 1.037 (9.4 brix) at 10 gallons (exact)
Postboil was at 1.048 (12.3 brix) at 6.85 gallons
Boiled off 3.15 gallons over the 70 minute boil.
Left about a gallon in the brew kettle (trub/hops).
5.8 gallons into the fermenter.
If I calculate the projected postboil volume from the preboil numbers, I get 370 gravity units in preboil. This divided into the postboil volume says that my postboil gravity should be 1.054. I measure 1.048, why?
My measurements are pretty accurate and samples are cooled to the hydrometer's calibration temp (68F). I also use a calibrated refractometer while actually brewing. The two instruments always tell me the same numbers. Also, my volume measurements are accurate within about 0.1 gallons (maybe 0.25 at worst).
Any ideas where my GUs are going? This has happened for all my batches and isn't a linear error. Sometimes real bad (18 points low on a RIS), sometimes not (1 point low on a blonde ale). Thanks!
First things first, love the HBT forums, you guys have answered so many of my questions over that past 6 months. That being said, I have a major annoyance I was hoping someone could help me out with. I can never accurately calculate my post boil gravity, no matter how accurately I measure my preboil. Here's yesterday's batch as an example:
Preboil was at 1.037 (9.4 brix) at 10 gallons (exact)
Postboil was at 1.048 (12.3 brix) at 6.85 gallons
Boiled off 3.15 gallons over the 70 minute boil.
Left about a gallon in the brew kettle (trub/hops).
5.8 gallons into the fermenter.
If I calculate the projected postboil volume from the preboil numbers, I get 370 gravity units in preboil. This divided into the postboil volume says that my postboil gravity should be 1.054. I measure 1.048, why?
My measurements are pretty accurate and samples are cooled to the hydrometer's calibration temp (68F). I also use a calibrated refractometer while actually brewing. The two instruments always tell me the same numbers. Also, my volume measurements are accurate within about 0.1 gallons (maybe 0.25 at worst).
Any ideas where my GUs are going? This has happened for all my batches and isn't a linear error. Sometimes real bad (18 points low on a RIS), sometimes not (1 point low on a blonde ale). Thanks!