Pre Boil vs. OG

[Toy4Rick]

Hey gang,

Is there a direct corelation between Pre boil gravity and OG? Meaning, a 1 hour boil in same equipment, similiar boil rate... will produce "x" increase in gravity?

I seem to float between .05 and .09 over the past 6 brews. Today seemed to be of the lowest and I am not sure why

Thanks in advance
Toy4Rick

 

[pcollins]

Usually, yes.

Atmospheric pressure, humidity, temperature, etc., all have a bearing on your boil off rate. As you brew more you'll figure out your average but there will be lows and highs. It's not fixed.

 

[Xpertskir]

Yes but it's not linear in fact I think it's parabolic.

Gravity is the measure of the density of sugar in water so

A pre boil gravity of 1.040 is not going to increase as much over the same boil off rate as a 1.050 pre boil gravity.