Is efficiency calculated before or after boiling the wort?

[javert]

This has been killing me. Last batch we were using an all-grain stout recipe, aiming for 6 gallons of wort for boiling and after the 1 hour boil we got 5 gallons so 1 of those was probably lost on evaporation.

The question is: are the gallons to be used in the PPG calculations supposed to be the ones before boiling (6 gal) or the ones after it (5 gal)? I'll try to explain myself with an example of our last batch:

8 lb 6 row base malt
0,5 lb crystal malt 60 °L
0,5 lb chocolate malt (YES: we screwed up here by weighing it twice instead of 0,5 and 0,5 lb of roasted malted barley)

Given yields of 35, 34 and 28 PPG, I would expect a OG of 1,052 for 6 gal and 1,062 for 5 gal or wort.

Which quantity should i use for calculations? Should I use the final 5 gal of wort and use 1,062 as the 100 % reference efficiency or should I use the 6 gal of preboil wort and use a efficiency factor that comprises both mash efficiency preboil and overall efficiency after boil?

EDIT: it was 0,5 lb of the other two malts and not 1 lb. My bad. The previous 1,064 value is now 1,062.

 

[Jim311]

You use the final product (wort) and measure the gravity of that if you're trying to determine your brewhouse efficiency. In this case, that's the 1.064 number. Note that the gravity increases as the volume of wort decreases. This is why boil off is important in brewing when you build your recipes.