Beer Forum

I have upgraded to a 15 gallon kettle and will be using it for 5 gallon batches until I can get something setup for temp control for 10 gallon batches. I wanted to know if the surface area is going to increase my evaporation. If so is there a way to calculate this or should I just boil water for and hour to calculate the evaporation?

If there is indeed an increase in surface area and not just an increase in head space, then yes the evaporation rate will increase. I think there are complicated formulas out there to figure it but it will take less time and brain strain just to boil some water and figure it out there.

One thing to keep in mind is to figure your rate as a volume per hour rather than percent per hour. If you get a 20% boil off rate on 5 gallons, you will lose 1 gallon in that hour. If you boil 10 gallons in that same pot with the flame at the same intensity you will still lose only 1 gallon, not the 2 gallons that a 20% rate would indicate. Using the gallons per hour rate, you will have predictable evaporation loss regardless of the volume (again assuming same pot and same boil intensity).

Wayne

That makes sense. When speaking to some at my local homebrew store they were saying if I am using the 15 gallon kettle and doing a 5 gallon batch I would have more evaporation loss than using the same kettle for a 10 gallon batch due to the surface area. So if I wanted to end up with 6 gallons in the kettle I should start with 8-9 gallons and after an hour I would end up with the 6gallons. That seemed to be a bit high to me. I think I will just fire it up this weekend with water and see what happens.

Yes, measure accurately and you will save yourself a lot of headaches in the future.
Make a good measuring stick and use it, too.

I've got a big, long pipe that I use for measurement


Mylo

I have a good consistent boil off rate figured out so I measure carefully going into the brew pot. I check the gravity during the boil with a refractometer and stop the boil when I hit my target gravity. My final volume is always within a quart of what was projected, usually it is right on. I'm more concerned with the gravity than the volume.

Doing first wort hopping allows me to forgo the usual 15-20 minute additions so I don't have to worry about messing up the hop schedule if I have to cut the boil short or lengthen it.

Wayne

Mylo wrote:I've got a big, long pipe that I use for measurement


Mylo

Im gonna put my balls in it!!

The state was such a good show......Still waiting for the DVD release!