What does boil gravity mean?

[Rat Terrier]

I am currently reading John Palmer's How to Brew and in the book he has a chapter with a few of his favorite recipes. On each recipe he has the following, "Boil gravity for x gallons" (x being the number of gallons).

For example on recipe "Confident Bastard - American Strong Ale" Version : Extract and Steeping Grain" he has listed under Wort A, "Boil gravity of 3 gallons" 1.059.

What does boil gravity of 3 gallons 1.059 mean?

 

[Nosybear]

That means the three gallons of wort you are starting your boil with has a specific gravity of 1.059. The wort is more dense than water (specific gravity 1.000), the specific gravity is a measure of how much sugar is in the wort (dissolved solids, actually, because all of them contribute to the density of the wort).

 

[GFHomebrew]

Thatd be the same as brewersfriends pre boil gravity.

 

[Chaos home brewing]

It is measured with a hydrometer or refractometer.

 

[GFHomebrew]

It is measured with a hydrometer or refractometer.

Both or either will suffice.

I've not got a refractometer but less wort is needed to measure gravity and it's pre fermentation so no alcohol in suspension to scue the reading.