Post Boil OG confusion.

[Sarhoş Karga]

Hi all,
I might be doing something wrong but couldn't figure it out.
Today I have brewed a Baltic Porter.
All went accordingly to the recipe calculator until the post boil OG.
I have ended up with 10 points less OG (1.070 instead of 1.082)
I'd like to know what to check because even the sizes are correct.
Cheers,
Arslan

 

[Nosybear]

Hi all,
I might be doing something wrong but couldn't figure it out.
Today I have brewed a Baltic Porter.
All went accordingly to the recipe calculator until the post boil OG.
I have ended up with 10 points less OG (1.070 instead of 1.082)
I'd like to know what to check because even the sizes are correct.
Cheers,
Arslan
View attachment 8162

Likely the default conversion efficiency. The bigger the beer, the lower the efficiency but the default doesn't change. For really big beers I reduce the efficiency to between 65 and 68% and hit numbers. I don't know if there's a formula that relates efficiency to OG but if there is, worth looking into (hint, hint).

 

[Sarhoş Karga]

Likely the default conversion efficiency. The bigger the beer, the lower the efficiency but the default doesn't change. For really big beers I reduce the efficiency to between 65 and 68% and hit numbers. I don't know if there's a formula that relates efficiency to OG but if there is, worth looking into (hint, hint).

Thank you

 

[Pricelessbrewing]

The efficiency used by brewersfriend is either brewhouse (target: fermentor) or mash (target: kettle). This scales with the amount of grain per volume of wort, in an almost linear manner for most brewers on average, if you keep very good notes you can determine your scale.

The relationship between lbs of grain and lauter/mash/brewhouse efficiency can be found by charting data from places like braukaiser, or using his batch sparge spreadsheet.Or just go to https://pricelessbrewing.github.io/BiabCalc/#EfficiencyEvaluation, and scroll down where I did the work for you and take a look at the graph.

@Nosybear I don't think BF uses conversion efficiency anywhere, but if it does let me know because I haven't found it! Typical values would be 90-95%.

As far as not hitting your gravity, if the volume is correct then either the efficiency needs to be lowered to hit your target OG, or your process can be changed to improve the efficiency.

 

[Nosybear]

The efficiency used by brewersfriend is either brewhouse (target: fermentor) or mash (target: kettle). This scales with the amount of grain per volume of wort, in an almost linear manner for most brewers on average, if you keep very good notes you can determine your scale.

The relationship between lbs of grain and lauter/mash/brewhouse efficiency can be found by charting data from places like braukaiser, or using his batch sparge spreadsheet.Or just go to https://pricelessbrewing.github.io/BiabCalc/#EfficiencyEvaluation, and scroll down where I did the work for you and take a look at the graph.

@Nosybear I don't think BF uses conversion efficiency anywhere, but if it does let me know because I haven't found it! Typical values would be 90-95%.

As far as not hitting your gravity, if the volume is correct then either the efficiency needs to be lowered to hit your target OG, or your process can be changed to improve the efficiency.

First entry into a brew day, mash complete, gives the conversion efficiency.

 

[Pricelessbrewing]

First entry into a brew day, mash complete, gives the conversion efficiency.

Right, for measured values, but not as a user input for recipe formulation.

 

[Nosybear]

Got it, there's the profile and you can override it in the recipe builder.

 

[Sarhoş Karga]

Thank you for the answer.

As far as not hitting your gravity, if the volume is correct then either the efficiency needs to be lowered to hit your target OG, or your process can be changed to improve the efficiency.

What I couldn't really understand was, all numbers were matching (the highlighted part) until the end of boil. That is why I have asked the question.

 

[Stephane Maillet]

I believe I have encountered the same problem as you and I believe this is an issue with the software.

From your screenshot above, your pre-boil volume is 23 litres and your post-boil volume is 19 litres indicating a 4 liter boil-off. You then specify your batch size as 18 litres (fermenter volume) likely to represent that you are leaving 1 litre in the kettle. You specifying 18 litres in fermenter as opposed to 19 litres is likely causing issues for you.

Please see the attached pdf document. I have included descriptions and screenshots that support my argument. Bottom line, the original gravity should be based on the post-boil volume - not the fermenter volume if you have chosen to make this lower that your ending kettle volume. Because I chose a fermenter volume 1.5 gallons less than my ending kettle volume, I undershot my OG by 0.005.