gravity and volume

[juskojj]

So kinda of a nub question but what's the difference between runoff gravity, meas pre-boil gravity, measured OG, measured FG. I'm pretty sure OG is measured when you transfer the wort into the fermenter, FG is measured right before bottling/kegging but what's the difference between runoff gravity and pre-boil gravity? When would you measure it? I would venture to guess that runoff is taken right out of the mash tun after sparging or is it before sparging? Then I'm assuming pre-boil gravity is before you turn on the burner to start boiling right? I would assume your runoff would be different if you measure it before sparging or if you have to add water after sparging to hit boil volume.

oh one other question how do you measure the temperature of your tun and grains if you don't have an IR temp gun? or do you assume they are the temperature that's in the room?

Do anyone have a good way of measuring your boil volume, post boil ect.. probably easiest is using a calibrated stick to your pot? I can't mark the pots because we also use them for cooking....

 

[Bathtubbrewer]

You're essentially correct about the OG and FG. Runoff gravity is just that; it's the gravity of the runoff from the sparge, normally a fly sparge. So it's really a snapshot of the amount of sugar you're still getting from your mash at that point in your sparge and an indicator of when you can/should stop. The pre-boil gravity is the totality of all of your collected runoff as a whole before you start your boil. Boiling will cause evaporation, which will obviously raise your gravity, so take that measurement before boiling.

This might help. Radius and height are of the container your wort is in:

Pi x (radius x radius) x height = y cubic inches

Then:

y cubic inches/231 = gallons in your container


Hope this helps.

 

[IslandLizard]

[deleted]: double post

 

[IslandLizard]

[...] y cubic inches/231 = gallons in your container.

I miss metric...

In my kettle, each 1.5 inches of wort height represents a gallon. My stirring spoon is marked at those intervals.