• Welcome to the new forum! We upgraded our forum software with a host of new boards, capabilities and features. It is also more secure.
    Jump in and join the conversation! You can learn more about the upgrade and new features here.

Pre-boil gravity question

wizardofza

Apprentice
Joined
Mar 15, 2008
Messages
7
Reaction score
0
I'm noticing that the pre-boil gravity isn't what I expect it to be.

To take a simple recipe with only one grain, the pre-boil gravity is different than what I expected.

Pre-boil volume : 8 gallons
Extract Efficiency : 75%
10 lbs Belgian Pilsner Malt w/ extract potential of 1.036

BS gives me a pre-boil gravity of 1.043.  :eek:

This differs with the way I'm used to calculating gravity, which is :

extract potential in GU * amount in lbs / volume in gallons * extract efficiency %
( (36 * 10) / 8 ) * .75= 1.034

Where's the discrepancy?  Anyone have any ideas?

 
Can you attach that recipe?  I entered it into BS and est pre Boil is 1.034.

Mark
 
It's because your est mash efficiency is 94.6%.  Take a look at your mash tab.  Pre boil gravity uses est mash eff.  The 75% you have on the main page is total brewhouse efficiency which also takes fermenter losses, etc. into consideration.

(10*36*.946) / 8 = 1.043

Mark
 
Update your equipment profile.  BS uses brewhouse eff and loss to trub/chiller in there to calculate est. mash eff.  There may be more to it than that but this is what I have noticed. 

I set loss to trub/chiller to zero so that est mash efficiency is same as total efficiency.  I do have 3/4 gallon of loss under fermenter loss as that does not impact est. mash efficiency.

Take a gander here.

http://www.beersmith.com/forum/index.php/topic,5141.msg21417.html#msg21417

Mark
 
Mark - thanks for the quick reply. What sized batch and which type of fermenter do you loose 3/4 gallon?
 
Welcome!

It's just a worse case scenario.  I make a lot of IPA's so you do lose a bit more due to all the hops.  I drop hop with 5+ oz.  I do 5.5 gallon batches and use 6 gallon glass carboys as fermeters.

Mark
 
Back
Top