weighing wort to determine volume

[martinworswick]

i did a search for this and couldn't find anything which surprised me.
i want to accurately determine the amount of beer in my fermenter for pitching rates etc,if i know the weight of my empty fermenter and then i weigh it again with the wort in,deduct the weight of the fermenter and divide the remainder by the gravity am i correct in thinking this will give me an accurate measurement?
(i'm working in metric if that makes any difference)

following are assumed figures

fermenter is 5kg
total weight is 45 kg
wort is 40kg/1.050
=38.095 ltres

correct?

 

[Ryush806]

i did a search for this and couldn't find anything which surprised me.
i want to accurately determine the amount of beer in my fermenter for pitching rates etc,if i know the weight of my empty fermenter and then i weigh it again with the wort in,deduct the weight of the fermenter and divide the remainder by the gravity am i correct in thinking this will give me an accurate measurement?
(i'm working in metric if that makes any difference)

following are assumed figures

fermenter is 5kg
total weight is 45 kg
wort is 40kg/1.050
=38.095 ltres

correct?

You are correct. Just keep in mind that the accuracy of your calculation will be determined by the accuracy of your scale.

 

[martinworswick]

cheers,

i thought so but there was doubt in my mind,any scales would be more accurate than my current method of guessing the amount of trub left in the bottom of the kettle!

 

[Ryush806]

cheers,

i thought so but there was doubt in my mind,any scales would be more accurate than my current method of guessing the amount of trub left in the bottom of the kettle!

You could always measure out 5 L (or whatever measurement) and pour it into your carboy. Then mark that spot and repeat until you fill your carboy. That way you can get a pretty good estimate of the volume to use as a sanity check after you make your calculations.

 

[martinworswick]

i use stainless kegs for fermenting so the more obvious/easier methods don't work so well when you can't see inside,i'mm now going to go and search for cheap accurate scales! preferably the luggage type so i can hang the keg from them.

 

[Ryush806]

i use stainless kegs for fermenting so the more obvious/easier methods don't work so well when you can't see inside,i'mm now going to go and search for cheap accurate scales! preferably the luggage type so i can hang the keg from them.

Ah that makes sense. Good luck on your scale hunt!

 

[CastleHollow]

If you have enough room to insert a graduated dipstick or retractable ruler into the keg, you can still go with Ryush806's suggestion. Pour water in liter increments and take measurements as you go.

 

[martinworswick]

i could do but its another thing to sanitise then another thing to clean,both of those are on my list of unenjoyable brew day jobs

 

[Ryush806]

i could do but its another thing to sanitise then another thing to clean,both of those are on my list of unenjoyable brew day jobs

I hear ya there! Once you get your scale, you might think about putting a known volume of water in there and weighing it to check the calculations. If the scale is off a bit, you could make note of how much its off and compensate for it later. If you want to get super sciency you could even make a calibration curve from say 35-45 L. Just depends on how exact you want to be with it. Really for using this to calculate how much yeast to pitch it really doesn't matter too much as long as you're close.