Are there any secret tricks to avoiding an exorbitant amount of soot on the brew kettle after the boil?
We have been making all grain batches recently using a 20 gallon stock pot and a propane burner, but we can never get the pot clean afterwards, so I'm finding black hand prints all over the house for weeks after brewing. The most recent batch we attempted to cover the bottom with aluminum foil; this was minimally successful.
The flame on your burner should be set such that it is almost totally blue, with just an occasional bit of yellow/orange. The soot is coming from having the gas/air mixture off-balance. If you see mostly yellow or orange flame, you are pretty much guaranteed to get soot on your kettle.
This will also severely affect your gas efficiency.
You may need to take your burner apart and clean the element with a scrub brush and some oven cleaner.
As far as I've understood, propane soots excessively when burned with too little oxygen - does your burner have some method of adjusting inflow of air?
I'll also quote a random forum post:
I was a Scoutmaster for many many years and found Fells Naptha bar soap to be the best for coating pots before cooking and for cleaning them after, even if you did not coat them first. I liked to shred some with a grater, put it in a plastic bottle with some water, and then use it after it dissolved.
Perhaps you can try the same with some heavy duty soap next time, though I can't speak for its effectiveness.
Like other answers have said, your burner's flame should be mostly light blue. The more yellow it is, the less efficient you are burning. Modify your mix to allow more oxygen and less fuel by either turning down the gas a touch, or opening the fuel-air mixing doo-hickey that most burners have.
If that STILL does not take care of the problem, get a bottle of dish soap. You want something that is as thick as possible. Squeeze some into your hand and rub on the sides/bottom of the pot. I've done this in cooking on a campfire, and it works like a charm. Just hose off the pot after you are finished and you are good to go!
The excess soot is from incomplete combustion of your propane (C₃H₈ + 5O₂ -> 3CO₂ + 4H₂O) is the complete combustion reaction. You need to increase the amount of oxygen, not propane. The flame should burn blue and non-luminescent. A yellow or orange flame indicates incomplete combustion and by products such as carbon monoxide (g) "CO" and solid carbon (s) "soot" deposited on the bottom of your burner.
Try buying a can of Barkeepers Friend. It's sold in most grocery stores, as well as Home Depot & Lowe's. It's a gritty, Comet style cleanser that doesn't scratch surfaces. Once I had soot build up from 3 different batches & Barkeepers friend took it off with one vigorous wash! I swear by it!
Just before washing, I rub off excess soot on the grass,it comes off easily and then use a steelo pad, scourer and soapy water or whatever other method you choose to use. This saves your dishcloth and your bench getting dirty as we all know how hard it is to remove these marks.
