Full Boil

So I am trying my first full boil batch in a couple of days. I am trying to base my recipe off of a similar recipe I have been reading in a book. This book says to start off with six gallons of water because throughout the whole process of steeping and boiling the wort it will evaporate down to 5 gallons. Does this sound correct? Does it have to be exact, because when I was doing kits and partial boils it said to make sure you add just enough water to be exactly at 5 gallons. So what would the consequences be of having too little or too much at the end of my boil? Thanks of the help and advice.

Consequences would be that you miss your target numbers. You'll be close enough though.

If you want to be sure. Take a gallon of water and bring it to a boil. Boil it for 15 minutes. Measure what is left. Take the difference and multiply by 4. Then you'll know exactly how much to add at first to end up with 5 gallons. (I would shoot for 5.25 gallons as hops suck some liquid up.)

I've been boiling 5 and topping off to 5 at the end.

You wont need to add much.

I do 6 or 6.25 and I get five gallons

The amount that boils off depends on several things.

1 - The size of your pot. If you have a tall and skinny pot it will boil off different from one that is shorter and fatter. This is relative to the surface area of the water.

2 - The length of time that you boil.

3 - The vigor of the boil. The more vigorous it is, the more water will be created to gas.

You'll only know how much to start with by trying it out. It can be very specific to your conditions.

eighteez said:

I've been boiling 5 and topping off to 5 at the end.

You wont need to add much.

Click to expand...

Technically, that is not a Full Boil.

Is the book called "Brewing Classic Styles?" If so, those recipes are designed for a 6 Gal full boil and, if I had the capacity, I would boil 6 Gal. The author (Jamil) is accounting on the volume lost in the boil as well as throughout fermentation.

I have used those recipes for partial boils (I don't have capacity for full boils).
I boiled 3.5 then topped off to 5.5 Gal (while checking OG to make sure I hit the target).

By the end of fermentation (omitting trub, volume lost to dry hopping, in the racking process, etc) I had just over 5 Gal going into bottles.

Hope this helps.