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I would like your input as to why my FG was far from the theoric on from brewer's friend calculator.

All Grain Pale Ale:

  • Maris Otter 4.7k
  • Roasted Barley 94 gr
  • Chinook 12 aau min 60
  • Cascasde 5 auu min 5
  • S-04 re-hydrated in one cup of water at room temperature

Batch Size 20L
- Wort: 12.9L
- water ph:6-7 I didn't have the machine yet, only with the papers
- Sparge:14.7L
- ph_wort_preBoil: 6
- ph_wort_postBoil: ~5

I use brewer's friend calculator and got these numbers for theory:
- OG_theory:1.053
- FG_theory:1.013

These are my real gravity numbers:
- OG_real:1.058
- FG_real:1.027

I use refractometer with ATC to meassure gravity.

Fermenting temperature was between 18°C and 22°C. I didn't have any problems during boil temperature-wise

From what I read, it could be the yeast so I was hoping you will have any input as to why I didn't get closer to the FG (I understand theory is only theory but still I'm far I think)

Thanks!

  • Is that preboil wort pH a measurement or calculation? pH6 seems high – brewchez May 15 at 23:46
  • yes, but it's aprox since I only had the strips then – D4n13l4 May 16 at 10:01
  • after you have transferred to a secondary, the fermentation rate goes down, and so ususally does the temperature. Boost the temperature up to 22-23 C and the fermentation should pick up until it slows down again. It should take less than a week in the secondary – Ken Dere May 17 at 15:15
  • 1) Did you shake or air-rate your work when or before the fermenter? 2) Did you test efficiency pre-boil? 3) fermentation time / length? – zatbusch May 18 at 9:32
  • 1.- Maybe not that much, after cooling when mixing the yeast with the wort I do it. 2.-nop, I'll read more about this because it wasn't considered. 3.-I started on May 1st and OG didn't changed since 8th (maybe 7 I don't have those days with me now) so I bottle on 14th. – D4n13l4 May 20 at 9:34
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Your pH of 6 preboil indicates that your pH was off the target during the mash. This likely favored alpha amylase activity over beta amylase. This led to a more dextrinous wort which would increase the amount of non fermentables, contribute more body and finally lead to a higher than anticipated/desired FG.

  • 1
    Except his actual FG is probably <1.010, see my other response. He used a refractometer for FG and did not adjust for the alcohol content. – dmtaylor May 20 at 13:49
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Refractometer does not read correctly when alcohol is present. It is important only to measure in Brix, never specific gravity. Then use the following conversion calculator to determine the true final gravity and alcohol by volume. Very very important fact that many people miss!

https://www.brewersfriend.com/refractometer-calculator/

Based on this calculator, I'm willing to bet the actual FG is very close to 1.009-1.010.

  • I have this one (aliexpress.com/item/…) – D4n13l4 May 16 at 9:23
  • I have that one too. Regardless, you need to follow my instructions above and the instructions at brewersfriend.com/refractometer-calculator – dmtaylor May 16 at 11:22
  • got it, but then it only means I'm farther from the FG so any ideas for how to fix this? – D4n13l4 May 16 at 12:33
  • Lots of ideas to try: Mash 2 C higher, mash for less time, try a different yeast, calibrate your mash thermometer. – dmtaylor May 16 at 13:35
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I would suggest using a temperature of 22-23 C, especially towards the end of the fermentations

  • what do you mean by end? after what days aprox? – D4n13l4 May 16 at 9:59
  • Please add more information to answer the question or post this as a comment. – Philippe May 24 at 16:57

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