Pre Boil and Post Boil

[J1791Hernandez]

Can someone please explain to me what Boil Size Pre: and Post: mean when editing recipes.

 

[Silver_Is_Money]

Pre-Boil Volume - Boil-Off Volume = Post Boil Volume
(Where all volumes measurements are taken at room temperature)

If you don't yet know your systems actual boil-off rate/volume, a Boil-Off rate of ~1 gallon (~3.8L) per hour of boiling is a generally safe starting presumption for a "rolling" boil. A mild boil may reduce this down to ~0.75 gallons per hour of boiling. The width of the kettle has a lot to do with the boil off rate. A wider kettle will boil off at a higher rate than a narrower kettle...

Volume as measured "at boiling" is 'roughly' 1.041 times volume as measured at room temperature.

 

[Craigerrr]

You could do a test of your boil off rate with a measured amount of water, boil for one hour, then measure remaining water. The difference in the two volumes is your boil off rate.

 

[Hawkbox]

Basically what they said. Pre is before you boil, post is what is left over after.