Pre Boil vs. OG
 

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

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.

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.