This was my third biab brew day and the first one where I tried the recipe listed above. I got a new kettle for Christmas so not only am I still learning the process for biab but I also had to get to grips with the kettle.
The brew day actually went very smoothly. The pre boil Gravity was 1.040 with the estimated value being 1.041. I was happy with this and knew that I had managed to keep a reasonably constant temperature throughout the 90 minute mash.
After the 90 boil I took another reading to see where I was up to with the og. The estimated value was 1.058, mine was 1.050. I'm hoping his will simply be down to a boil which wasn't as vigorous as it maybe should have been. Or potentially he evaporation figure needs to be tinkered with in BIABacus. Any other issues that I should be considering?
Given that it's only my third biab I'm not actually too concerned at being short on the og. I'm still learning and I know that once I have refined the processes I will be closer to the target values.
Post #2 made 10 years ago
c_squared...We really wouldn't be able to diagnose what happened without some more detail, but I'm not sure that is what you're looking for. If it is, a few things that occur to me...
1. You don't post any volumes... did you hit your pre boil and VAW numbers? Maybe the low gravity was due to low evaporation, and maybe not. If it was due to low evaporation, note that that figure can vary greatly from brew to brew.
2. How do you measure gravity? If it is with a hydrometer, are you measuring at 20°C? Are you measuring a few different times? You can't really trust 1 measurement with one instrument. Plus, if you are measuring gravity while the wort is still warm... your numbers will be low. If your pre boil volume and gravity were spot on at 20°C, and gravity of ambient wort was low but VAW was on... you have a measurement problem.
3. I agree with you not to sweat it. I wouldn't either... It could be a number of things... it could be nothing but inaccurate measurements. The beer will still be good!
Congrats on the brew and show pics when its done!!!
Jeff
1. You don't post any volumes... did you hit your pre boil and VAW numbers? Maybe the low gravity was due to low evaporation, and maybe not. If it was due to low evaporation, note that that figure can vary greatly from brew to brew.
2. How do you measure gravity? If it is with a hydrometer, are you measuring at 20°C? Are you measuring a few different times? You can't really trust 1 measurement with one instrument. Plus, if you are measuring gravity while the wort is still warm... your numbers will be low. If your pre boil volume and gravity were spot on at 20°C, and gravity of ambient wort was low but VAW was on... you have a measurement problem.
3. I agree with you not to sweat it. I wouldn't either... It could be a number of things... it could be nothing but inaccurate measurements. The beer will still be good!
Congrats on the brew and show pics when its done!!!
Jeff
Missed my og on NRB's Amarillo apa
Post #3 made 10 years ago
Thanks for the reply safebrew.
I hadn't posted any volumes because I wasn't sure I had them worked out accurately. I measured the headspace left in the kettle and used the conversion on BIABacus. The pre boil estimate was 20.74l, with my headspace measurement I was getting a value of 23.28l. I also forgot to take the VAW reading as I got focused on the transfer into the fermenter. However I know that my volume at flame out was 19.72, again, this was measured with headspace.
Maybe what would help is that the estimate for VIF was 12l. I've got 13.63l so quite a bit over.
I'm happy with how the brew day went and know that I can learn more with each brew I do. Hey, I may have slightly lower abv beer, but on a plus, I have more beer than I had originally planned.
As for he gravity readings. I had previously read about how temperature can throw the reading. For both pre and post boil I cooled the sample down to 20degrees before taking a reading. What I didn't do is run three or so samples so that's something I can consider for future brews.
I hadn't posted any volumes because I wasn't sure I had them worked out accurately. I measured the headspace left in the kettle and used the conversion on BIABacus. The pre boil estimate was 20.74l, with my headspace measurement I was getting a value of 23.28l. I also forgot to take the VAW reading as I got focused on the transfer into the fermenter. However I know that my volume at flame out was 19.72, again, this was measured with headspace.
Maybe what would help is that the estimate for VIF was 12l. I've got 13.63l so quite a bit over.
I'm happy with how the brew day went and know that I can learn more with each brew I do. Hey, I may have slightly lower abv beer, but on a plus, I have more beer than I had originally planned.
As for he gravity readings. I had previously read about how temperature can throw the reading. For both pre and post boil I cooled the sample down to 20degrees before taking a reading. What I didn't do is run three or so samples so that's something I can consider for future brews.
Post #4 made 10 years ago
c^2, It sounds like your main issue was that you had less boil-off/evaporation than expected. As safebrew said, this can vary considerably depending on the wind, temperature, or other conditions. 12/13.63 * 58 = 51, so your FG of 50 (1.050) is close to expectations. However, some of your measurements are questionable. A pre-boil volume of 23.28L vs 20.74L estimate is too big an error, and I seriously doubt you then had a VFO of 19.72L, as that's very little boil-off reduction. Finally, 19.72 VFO doesn't correlate with 13.63L VIF. 19.72 VFO should be ~18.9 VIF, which would mean you had an unusually high 6.3L KFL.c_squared wrote:The pre boil estimate was 20.74l, with my headspace measurement I was getting a value of 23.28l. I also forgot to take the VAW reading as I got focused on the transfer into the fermenter. However I know that my volume at flame out was 19.72, again, this was measured with headspace.
Maybe what would help is that the estimate for VIF was 12l. I've got 13.63l so quite a bit over.
So the bottom line is you probably just had lower evaporation, and you need to be as anal as possible in recording your volumes.
Last edited by cwier60 on 02 Feb 2015, 10:27, edited 1 time in total.
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Missed my og on NRB's Amarillo apa
Post #5 made 10 years ago
Thanks for the reply. I knew the volume measurements appeared all over the place. It's the first time I have tried to measure volumes so I know I have some work to do to get better at it, or just to simply make it work!
Missed my og on NRB's Amarillo apa
Post #6 made 10 years ago
Something else which has become a factor with the volume measurements. I hadn't measured the kettle dimensions, I just took what was quoted off the box and threw it into BIABacus. I decided to double check and the kettle is actually 1cm shorter in height than what the manufacturer stated. At a glance on biabacus, that reduces each volume value by just short of a litre.
Post #7 made 10 years ago
Yeah. it's really worth accurately measuring and even calibrating with some water and known volumes. Once you do that, assuming that the sidewalls of your kettle are straight (vertical), then you can accurately convert cm of depth or headspace to volume (except for the very bottom which is slightly different due to the curvature. Some people make a measuring depth stick and others just measure the headspace to the wort level.
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Missed my og on NRB's Amarillo apa
Post #8 made 10 years ago
Yep, the kettle has vertical sides. I was thinking about doing a calibration exercise to be able to know for certain what volume I had.
This may seem like a totally crazy question but should I do that calibration for both hot and cold volumes or is that a step too far?
This may seem like a totally crazy question but should I do that calibration for both hot and cold volumes or is that a step too far?
Post #9 made 10 years ago
That's unnecessary. You just need volumes. BIABacus accounts for the volume difference due to temperature (which typically is ~2/4% increase in volume from typical ambient and typical mash or boil temps). For example SWN & TWN are the same volumes at different temps, as are VFO and VAW.c_squared wrote:This may seem like a totally crazy question but should I do that calibration for both hot and cold volumes or is that a step too far?
Last edited by cwier60 on 03 Feb 2015, 04:56, edited 1 time in total.
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