Pre-Boil to OG -Small Increase

[tbone]

The last two AG beers had what I believe to be small increases in SG from "Into the Brew Pot to Into the Fermenter". For example I did a Pale Ale that had a Pre-Boil SG of 1.043 and an OG of 1.048. Beersmith estimates were 1.036 and 1.051 based on 75% efficiency. I did a strong boil for 60 minutes. Assuming that my measurments are correct, what are the factors that could cause this?

 

[MN_Jay]

Are you asking why you are getting an increase or why it doesn't match beersmith? If its' the latter, a couple things come to mind, different pre and post boil volume than beersmith, also different evaporation rate than beersmith.

 

[Yooper]

When I first starting using Beersmith, my post boil didn't match either, but I changed the settings to my realistic evaporation rate. I don't boil off much, maybe .5 gallon, since I brew inside.

It could be that your preboil efficiency is off because of your efficiency, but the post boil could be off due to evaporation rate, stuff left behind in the kettle, etc.

 

[tbone]

Am I correct in saying that the more you boil off, the higher your OG should be because of less volume?

 

[MN_Jay]

Exactly. The wort is more dense, thus higher OG

 

[Ecnerwal]

Some water leaves (as vapor), the sugar stays put, things get more concentrated - that is the way it works.