Re: Kettles, Cleaners, Conductivity.

Jim, Not trying to debate science but your response generated a question that I hope is easily answered about thermal conductivity. Possibly an experiment over a beer would be helpful. Trying to better understand the aluminum vs SS debate. Some folks use Rocket Engines to heat kettles. Others use electrical elements. A few of us rely on small gas burners that seem to outperform many of the higher BTU producers. According to your statistics, aluminum is 11.25 times more conductive than SS. Is it accurate to state that an aluminum stock pot would transfer 11 times more heat to the liquid that the SS version using the same external heating device? Would it be logical to conclude you would use 11 times less input heat with aluminum than SS to achieve the same degree of "rolling boil?" To validate this, would a "heat to boil race" be appropriate? Two gallons in aluminum, two gallons in SS. Original water temperature 60°F. Similar profile containers with identical burners (15 kbtu). Both burners started at the same time. If the aluminum boils in 5 minutes, then the SS boils in 56 minutes? I have never had trouble with scorching but use a diffused flame source with about 100 single hole jets. I do notice more accumulations of beer stone, hard calcium deposits (white), and general brown crud directly over the iron supports. They must significantly help with heat transfer. The false bottom for boiling is usually used only when you bitter with whole hops. The nice thing is it does not need to be in the boil for the complete cycle but performs very well with Irish moss. If it is not yet installed, you can scrape clean the bottom of the kettle and cut back even more on your input BTU's. If you leave a little space between perforated plate and edge, you get a great roll in your kettle and the perforations appear to hold the hot break quite solidly. Must be experiment time. Stay tuned - don't touch that dial! I look forward to data about flame impingement and actual heat transfer! Thanks Jim for kicking this off again! Rick O Rick Oftel Greetings, I started out w/ Keg-kettles w/ heating elements and spigots. I direct fired the kegtle, in addition to the electircal heat. Never did a decoction in these elemented kettles, can't really stir w/ the element in place. The Polarware SS Kettles are much better than converted kegs. For a direct fired brew kettle, I find aluminum to be superior to stainless. Isssues as I see 'em. 1. Conductivity, hot spots, scorching: Materail Conductivity Cost (W/m-^C) (From Matweb) Copper 360 $1kb? Aluminum 180 $100 400 SS 27 $100 300/18-8 SS 16 $200 I've never used copper, but in my experience, aluminum is a superior conductor compared to SS. Granted the Al needs to be a bit thicker, so the actual conductivity may be only 5 times the values for the Polarware pot. The chances of scorching are much lower w/ aluminum. Aluminum works much better for decoction mashing. A thicker, better conductor means fewer/no hot spots. 2. Cleaning. Commercially, aluminum is not a good option since the commercial cleaners (strong caustics) dissolve aluminum, but few compmercial operations are direct fired. Also, commercial brewing is a high risk occupation. (get the numbers from OSHA if you don't believe it.) Number one hazard is burns, from the strong caustics used in cleaning. My question is this. What sort of chemicals are you using on your home brew kettle? Why? My aluminum kettles take a bit of beer stone, and keep it until I over-do the acid/pH adjustment. 3. I'm not a fan of spigots in the brewkettle. Impossible to clean, and easily plugged. I like the siphon/duck/whatever. 4. I'm not a fan of false bottoms. Never worked that well in the mash tunn (Sabco), so I'm back to slotted pipes in a cooler. In the kettle, I've had trouble w/ scorcing under the false bottom (Sabco). Quite possibly, that issue is reduced or eliminated w/ a "real" kettle. (e.g. Polarware). 5. Flavor: Not an issue. See Jeff Donahue's article on same. My keg kettls are wired for heat (1100 watts at 110v) and have spigots. I've retired them "upstairs) to HLT use, and they work fine for that. A spigot on the HLT is very convenient. I'm as big a fan of stainless as the next guy, but it's not a very good conductor. Cheers, Jim -- ------------------------------ * * Dr. James Lee Ellingson, Adjunct Professor jellings(a)me.umn.edu * * University of Minnesota, tel: 651/645-0753 fax 651 XXX XXXX * * Great Lakes Brewing News, 1569 Laurel Ave., St. Paul, MN 55104 *