Pre-boil Gravity And Hop Additions

[Dazza_devil]

Evenin Brewers,
Rather than doing full volume boils at the moment, I'm adding LDME and chilled water after the boil to achieve target OG. When formulating partial recipes from AG recipes, do I adjust my pre-boil gravity to the target gravity or somehow calculate a similar pre-boil gravity to that of the recipe to achieve the specific bitterness and hop profile?

 

[Rodolphe01]

The hop utilisation is based on the gravity of wort they are boiled in, so i'd be be basing it all on your actual (or predicted) boil gravity. The balance of the beer (i.e. bitterness, malt, sweet etc) should all work out once you dilute, I assume you are using beersmith or something, so just use that to ensure you final volume once diluted has the correct IBU and gravity.

You could also experiment with making your boil of a low gravity, thereby requiring less hops... Before I went full volume boil that was something I wanted to play around with, all to save $0.50 on bittering hops

 

[Dazza_devil]

The hop utilisation is based on the gravity of wort they are boiled in, so i'd be be basing it all on your actual (or predicted) boil gravity. The balance of the beer (i.e. bitterness, malt, sweet etc) should all work out once you dilute, I assume you are using beersmith or something, so just use that to ensure you final volume once diluted has the correct IBU and gravity.

You could also experiment with making your boil of a low gravity, thereby requiring less hops... Before I went full volume boil that was something I wanted to play around with, all to save $0.50 on bittering hops

I'm not using any recipe programmes.
With my method I adjust my pre-boil gravity with either water or LDME, whichever is needed to achieve the required gravity.
I just wanted to use AG recipes as they were, so I need to calculate the pre-boil gravity to use the same amount of hops that the recipe uses. Obviously the hop utilisation will be dependant on pre-boil gravity but when doing partials my boil quantities will be different as will my evaporation rates. Do I just attempt to achieve a pre-boil gravity using around 10% evoparation from the target gravity?