Partial Specific Gravity?

[Wwiillburr]

I appologize because I'm sure this has been answered somewhere, but I'm not exactly sure how to search for it cause I dont know what I'm talking about.

But my question is, if I boil 1.5 gallons and take the specific gravity of just that 1.5 gallons, how can I know what the specific gravity of all 5 gallons would be?

Thanks!

 

[ericm]

assuming you don't lose any wort, and assuming your volume measurements are accurate,

gravity of 5 gallons = (gravity of 1.5 gallons * 1.5)/5

(gravity1*volume1 = gravity2*volume2)

edit: forgot to mention, just take everything after the decimal point for the SGs (ie; 1.110 becomes 110, 1.048 becomes 48; so if you get 54 when you solve the equation, that means 1.054)

 

[dbowdit16]

You should be able to just do a weighted average. Multiply the SG of each fluid by the number of gallons of each fluid, add that together and divide by the total volume of the combined fluid.

Example: 1.18 (SG of wort) * 1.5 gal + 1 (SG of water) * 3.5 gal = 5.27/5 gal of total fluid = 1.054 SG of 5 gal mixed wort

 

[Wwiillburr]

Thanks for the quick responses! Looks like my original gravity is 1.049. That sounds about what I expected.

I'm in the process of making a MLT so I am excited about going AG, but in the meantime I wanted to do a quick extract brew and it had been 2 years so I had forgotten a bunch. Thanks again