OG before top off

[kirbykollege]

How much us it affected adding 1/2 gallon of water? Do you usually take it before or after?

 

[WoodlandBrew]

OG should be measured with the full volume of water before you pitch the yeast. There is a linear relationship between specific gravity and water volume. So if you measure before toping off with 1/2 gallon (in a 5 gallon batch) the number you measure will be 10% high.

 

[Golddiggie]

I wouldn't bother adding just 1/2 gallon to my batch.

 

[Unibrow]

Always take your OG reading AFTER topping off + mixing it in well if you want the most accurate number.

 

[Odin_Brews]

Your OG is taken after topping off and a really good stir to make sure the wort is mixed and homogeneous (so you dont get a false reading). How much it is affected depends on the actual SG and volume. TO calculate;

Measured OG in pts / Final Volume * Meaured Volume before top up = Final OG in pts

OG in pts meaning 1.050 is simply 50. It's basically the ratio: Volume before/Volume After multiplied by pts gravity...get it? You can also play around with it and say measure your post boil gravity and then calculate how much water to top up with in order to achieve a desired OG for the batch.

Hope that makes sense, Cheers