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Accounting for boil off

I’m looking to end up at 2 gallons of wort for a graf how do I account for boil off so I can reach this?

You will need to test boiloff in your system. The easiest way to do this is to boil a given volume of water in your system (dependent on your kettle size) for one hour. Then measure the remaining volume after it cools. The difference is your boiloff rate. Then you would apply this to your graf recipe to get your starting volume you would need to end up with 2 gallons at the end. You may need to account for volume loss in the kettle and post fermentation trub in the fermentor if you want to actually finish with 2 gallons but it depends on how specific you want it to be. For most of my beers I aim for .25 to .5 gallon over my 5 gallon target depending on hop load and my system boils off 1 gal/hour so for a 5 gallon batch, I start around 6.25 gallons into the carboy.


Amount of boil off depends mostly on the vigor of your boil and the shape of your kettle. Applying a lot of heat to the kettle so you have constant mini volcanoes will have a higher boil off rate than when only half of the surface is kept at a rolling boil.

A larger diameter kettle will have a greater boil off rate than a narrower kettle. This is a function of the surface area of the wort.

Best way to determine your boil off rate is to boil water for the same amount of time you would boil your wort and measure the volume remaining.

thanks, I’ll do that my next brew day.

Helps to have volume markings in the kettle or something to measure with so you can adjust the heat according to where you want to finish.

good idea, I’ll look for that in a kettle when I buy a larger one

Not too hard to etch the inside of a stainless kettle with volume marks - there’s a really good article out there, hit up your favorite search engine and it should be right at the top.

Oh that will be fun! Thanks

I do lose about. 1/2 gallon during the boil. End up with 5.5 gallon of brew at the end of the session. Start out. With. A6.5 gall boil. Me did a experiment. Did boil. 6.5 gall water for 60 min. Than did transfer to messure bucket. Right at the 5.5 mark

well I lost a little under a gallon. so now I know, thanks for the future proofing tips everyone. I hope I can afford a burner/10 gallon kettle soon.

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