Originally Posted by Kilgore_Trout
Sounds like 10 gallon batches are in your future....
It will work OK as long as you can boil it well!
You'll get more boiloff from the increased surface area, but that's about it.
You got that right that 18" diameter has 254 sq/in surface area, a 12" cut top keggle 113 sq/in area, a 10" cut top keggle at 78.5 sq/in area.
A 10" to 18" 3.24 times in area increase, 12" to 18" 2.25 times in area increase. Wind, air temps, humidity plus boil time 60 or 90 minutes plus how strong of a rolling boil your boil losses may vary by a large amount. YMMV as they say. Time for a boil test with water, not exactly the same as with a wort boil. This brings up another question, respect to the original posted thread i'll start my own thread almost parallel to this topic.