Pre-boil gravity much higher than predicted by Brewer's F

[DylanD]

Hi,
The last two brews I have made had the pre-boil gravity much higher than predicted. I have always been in the ball-park with my brews, but last two were wildly different.
My Munich Dunkel was supposed to be 1.037 before boiling but turned out to be 1.050 before boil!
Here is the link to the recipe.
<iframe width="100%" height="500px" src="https://www.brewersfriend.com/homebrew/recipe/embed/1342443" frameborder="0"></iframe>

• Nothing fancy, 90minutes mash @65C (was 63C towards the end)
• 4 kg Munich - Light 10L 33 10 72.7%
  1 kg German - Bohemian Pilsner 38 1.9 18.2%
  0.25 kg United Kingdom - Crystal 60L 34 60 4.5%
  0.25 kg Rice Hulls 0 0 4.5%
  
  
• Actual Lovibond on Munich packet was 6.2, is 10 on the calculator.
• I got the expected volume of 1st & second runnings.

Where the hell did all that sugar come from????
Any help much appreciated.
Dylan

PS The same sort of thing happened with my PILS recipe:
<iframe width="100%" height="500px" src="https://www.brewersfriend.com/homebrew/recipe/embed/1332569" frameborder="0"></iframe>
This one had a more ambitious triple decoction method, so harder to deconstruct I suppose, but still, wildly higher pre-boil gravity.

 

[Sandy Feet]

Was just the pre boil off or was the OG was off too?
I normally don't take pre boil readings anymore as I used to get high readings when the brew bag was in the kettle. I am also comfortable with my efficiency settings. The main reasons for getting different gravity readings are the grain crush (big reason), the mash temperatures, and adjuncts. If BIAB, squeezing the crap out of the bag will make some difference too.
I was all over the place when I had to change homebrew shops. Now, I am fairly consistent.

 

[Herm brews]

Do you mill your grains, or buy them already crushed? If you buy them crushed, maybe something changed with your supplier?

 

[Minbari]

When you measure, how much volume of product is there and what is expected by the program. If you have 4.5 gallons of wort, but it assumes 5 gallons, then the gravity will be higher than calculated

 

[DylanD]

Thank you all for for replying.
I didn’t measure post-boil OG. I panicked and started adding water as it was boiling, so I can’t easily work out whether boiling would have corrected it (I assumed it was going to rise like it did with my sweet Pilsner!). Looking back I should have just boiled it, taken the OG, and added some boiling water to bring OG down to what I wanted.
I buy ready milled grain, and mash without a bag. I will look into buying a mill, and some calming medicine to stop me making crazy decisions in the heat of brewing!
Thanks again
Dylan

 

[HighVoltageMan!]

Your efficiency in your recipe calculator is too low. It should be @ 84% not 70%. This will get you more accurate numbers.

 

[Craigerrr]

Welcome Dylan!

 

[DylanD]

Thank you for the tip with the efficiency, I will change it on my system when I get a chance, and thank you for the welcome & advice. Iechyd da from Wales!

 

[Craigerrr]

And good health to you as well sir (thank you Google translate)

 

[Donoroto]

The Google unites us all.