Way to much to boil

I must have figure my boil off rates way wrong, because on a american wheat five gal batch i put 12 gallons into the boil kettle. I did think anything of it at first so i went along with the first hop addition, an ounce of cascade. What will the effect be on the bitterness of the cascade? I did plan on a ninety minute boil, however I am ninety minutes in and i still need to boil off two more gallons, what a freaking night!

Well, you won't get any more hop utilization after a point, and you're going to get at on of malliard reactions, resulting in a more caramelized wort, but you can boil for that long. Just the things I said will take place. And you'll waste a lot of gas.

Umm...seriously? 12 gallons of wort and you're trying to get to 5G? What is/was the gravity of the 12G? If it is even remotely normal, I'd just say make a 10G batch instead and fix it next time.

I was using my new converted keg as a boil pot, and i was way to distracted. I thought i figured my boil off rate at 30% but i was way off. the gravity of the wert was 1.020 when i had about 10 gal in the pot. After a lot of boiling i got the wert down to six gal and hit my og right on 1.040. Needless to say i will be doing another boil off rate test today.

you should get between 1.25 and 1.5 gals per hour evaporation from a keggle. so with the 90 minutes you should lose 2-2.25 gals. if you are losing more then that you need to cut the gas back some. 5 gals + 2.25 = 7.25 gals + 4% shrinkage you can figure the 7.5 gal mark

I want the burner he's got!!! Seriously, you go down from 12 gallons to 7 in 90 minutes, that alone is impressive.