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50L Braumeister - Poor Post Boil Gravity

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cliffo

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Hi All,

I've just finished my 3rd brew on my 50L Braumeister and am noticing a trend in relation to pre and post boil gravity readings.

My latest brew had a pre boil reading of 1.040 (Beersmith estimated I'd get 1.041 so near enough) but after a 90 minute boil and boil off of 12 litres (56L down to 43L) my gravity reading was a mere 1.042 (Beersmith estimated I'd hit 1.051).

Both readings were temp corrected to the 20 degrees of my hydrometer and my refractometer confirmed these figures.

Looking at the figures for my last brew, I had a pre boil gravity of 1.041 (bang on what Beersmith estimated) and post boil reading of only 1.043 following a 60 minute boil (Beersmith estimated 1.048).

Both times my volumes were either what I was aiming for or a little bit higher but post boil the gravity readings have barely moved.

Would anyone have any ideas about what is possibly going on here?

Cheers,
cliffo
 

QldKev

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What volume did Beersmith have for post boil?


edit:
Actually this doesn't add up?

1.040 @ 56L, reducing to 43L
40 / 43 * 56 = 52,
aka 1.052 so the same as BeerSmith...


double edit: are you measuring the left over crap from the kettle post-boil?
ie. vol in kettle post-boil or vol into fermenter.
 

tallie

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If you are confident with your volume measurements, then something is wrong with your hydrometer/refrac readings. In the same vein as what I mentioned in this thread, if you are really losing 12/13L to evaporation, you are concentrating the wort by an inversely proportional factor, so at least one of those numbers is wrong (assuming same environmental constants).

So,
  • Do both the hydro and refrac read 1.000 in water at 20°C?
  • Are you cooling the wort down to 20°C to take a reading, or are you using a calculator to make the adjustment?
  • If the latter, are you sure the calculation is using °C, and not °F?
  • How confident are you with the accuracy of your thermometer?

Cheers,
tallie
 

NewtownClown

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Sugar Gremlins. They get into my chocolate, as well...
 

cliffo

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QldKev - Vol is what is in the fermenter. I had 1.5-2 litres of crap left in the BM (have Beersmith set up for 2L losses to kettle). Whilst my volumes are indicating aliens are not stealing my beer, they may be stealing the sugars within!

tallie said:
  • Do both the hydro and refrac read 1.000 in water at 20°C?
  • Are you cooling the wort down to 20°C to take a reading, or are you using a calculator to make the adjustment?
  • If the latter, are you sure the calculation is using °C, and not °F?
  • How confident are you with the accuracy of your thermometer?

Cheers,
tallie
  • I've just checked the hydro and refrac in distilled water and both read 1.000 at 20°C (had to cool the samples to 20)
  • I did both - adjusted the reading using BS tool and also cooled wort to 20°C, both gave the same figure
  • Definitely in °C
  • I used the reading from the BM, probe in my fermenter and a stick thermometer. All were within 1 degree of each other.

It will no doubt be something simple that I'm missing or miscalculating but the fact that I hit the right pre-boil gravity but no where near post-boil figure is doing my head in.

If both readings were out I'd be questioning my measuring equipment.

Puzzled!

cliffo
 

Florian

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Sure your kettle loss is right? 2L would equate to next to nothing in height.
I'd check that first and then the markings on the fermenter.

my guess is that you didn't have much boil off and therefore not much gravity win. Still, those numbers seem odd.
 

cliffo

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Florian said:
Sure your kettle loss is right? 2L would equate to next to nothing in height.
I'd check that first and then the markings on the fermenter.

my guess is that you didn't have much boil off and therefore not much gravity win. Still, those numbers seem odd.
I fashioned a pick up tube from a copper elbow and two lengths of silicone tubing, the bottom of which sits just above the floor of the BM and drains it pretty well to the bottom level of the tube.

What's left is mostly trub.

Next brew I think I'll have to extra pedantic about all my measurements just in case I've missed something though I'm confident my volumes are sound.
 

lylo

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cliffo, did you solve your problem?
I have had the same thing happen to me and I am quite sure it was because I took my sample from the drain on the kettle without giving a good stir. I had EOB gravity readings go down !! because of this mistake.
BTW my BM 20liter is on its way from California and should have it in a couple of days!!
That is the main reason for this post. I can't wait!!
 

Screwtop

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Interesting............. How do you measure your preboil volume in the BM?. What volume of water did you use for mash in, and what weight was your grainbill?

Provided you are confident your measured mash in volume is correct, allowing 1L per Kg for grain absorbtion following removal should provide a guestimate of preboil volume. Physics at play here, not aliens :D

Screwy
 

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