Another newbie hydrometer question

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Chris-18

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Alright, so I have another newbie hydrometer question.
I posted a question about adding water to the wort before fermenting a while back, which made me think about a potential mistake I made.

When brewing, I can't figure out how you adjust specific gravity.
When you finished the boil, the gravity in my brews have always been way to high because I boiled off water. And the recipes called for adding water afterwards. And I did so I ended up with the amount of liquid the recipe called for. But one time the gravity was supposed to be 1. 054 and I had 1.46. So I must have added too much water.
But how do you guys figure our exactly how much water to add? How much that boils off, must vary from time to time.

The only way I can figure out, is to take hydrometer readings all the time after you add x amount of water. But that seems like a big pain in the ass.
Is there a smarter way that I just haven't thought of. Or do you just work with the gravity you get, no matter if it's too high or too low?
 
If you're using extract, you just use the top up water to get to the volume specified in the recipe.

Since water boils off, but sugar does not, if a recipe using extract says to expect 1.050, if you use that recipe and top it up to 5 gallons, the OG has to be 1.050. Extract has a set amount of sugar in it that doesn't go away.

I have volume markings on my kettle. I put it on with old nail polish, so it wasn't fancy, but others etch or otherwise mark their kettle. I also put volume markings on my fermenter. So I can see at a glance how much I have and how much I need.

For all grain brewing, water is not usually used to top off at the end of the boil so any adjusting is done pre-boil.
 
Although @Yooper is correct that your recipe should give you the exact volume at the specified gravity, since sugar doesn't boil off, there can be trub losses. Any amount of trub left in your boil kettle, usually hop pulp in extract brews, is suspended in (high gravity) wort that doesn't make it into your fermentor, and is lost, unless you can reclaim it. There are ways.

I would use a hand or online calculator or spreadsheet function to find out how much water to add to an x volume of y gravity wort to obtain your target recipe original gravity (OG). It's really simple:

V1 x G1 = V2 x G2
or
V2 = V1 x G1 / G2

V2 - V1 would be the amount of water to add.

Just use the last 2 (or 3) digits in your gravity calcs, e.g., for 1.058 use 58, also called "points."
 
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