How to Average Gravities

[Weissbier]

I'm not even sure if this is possible, but is it possible to average specific gravities take with different volumes? I didn't take a gravity reading into my boiler, but did at different stages of my mash. Thanks!

I have..

2 Gallons @ 1.081
2 Gallons @ 1.044
3.5 Gallons @ 1.016

 

[Catt22]

IMO, not really, but you might be able to come up with a very crude approximation using those numbers. I don't see the point in doing so though. You can take both a gravity reading and a hydrometer reading and back into the OG with some brewing software such as ProMash. I have done this on occasion. I use Promash and I could plug the numbers in if you would like.

 

[Weissbier]

If you wouldn't mind. I think I am in the range of 1.041~

 

[Catt22]

Draw a sample and post both the refractometer reading and a hydrometer reading. Need both to back into the OG once fermentation is under way.

 

[Barc]

Assuming your hydrometer readings are accurate, you can just add totals of each volume times the reading and then divide the sum by the total volume:

2 X 1.081 = 2.162
2 X 1.044 = 2.088
3.5 X 1.016 = 3.556

Add the results.

7.806

Divide by 7.5 gallons.

= 1.0408

So, your OG reading (going into the boiler) should be somewhere in the neighborhood of 1.041...

Hope that helps!

 

[david_42]

It's a little easier to follow if you just work with the points:

81x2 = 162
44x2 = 88
16x3.5 = 56

306/7.5 ~= 41

and

306/5.5 ~= 56

Fairly close to my standard 1/2, 1/3, 1/6th (of the sugars).

 

[homebrewer_99]

Is this all the same batch? I'm assuming its not since the last one is almost twice the volume of the previous two.

By averaging gravities do you plan on blending them eventually?

If that is the case, then I can say with some certainty that at least one of the yeasts will continue to ferment out the higher gravity batches.

Unless you allow the yeast to re-ferment the other batches (out all the way to its FG) you may be setting yourself up for overpressures in the bottle resulting in bottle grenades.

Did you think about that?

 

[Weissbier]

Thanks for the help guys, I figured it was as simple as averaging them out but just wanted to make sure.

Is this all the same batch? I'm assuming its not since the last one is almost twice the volume of the previous two.

By averaging gravities do you plan on blending them eventually?

If that is the case, then I can say with some certainty that at least one of the yeasts will continue to ferment out the higher gravity batches.

Unless you allow the yeast to re-ferment the other batches (out all the way to its FG) you may be setting yourself up for overpressures in the bottle resulting in bottle grenades.

Did you think about that?

This actually was all the same batch, a very big Belgian Wit. 7lbs of Bel Pils, 4lbs flaked wheat, 2lbs flaked oats...I was working on bringing up the efficiency by double batch sparging and getting my OG to the estimated 1.064. Since I ended up with 1.060 after a 90 minute mash and boil I think I did pretty good.