Kettle Shopping
I’ve been shopping kettles recently – actually I’m in the process of a brewery upgrade. I already have a really great kettle for boiling – a 15 gallon stainless steel Megapot. The marketing spiel on the Northern Brewer site describes it like this –
Northern Brewer’s famous Megapots are a homebrewing standard. These are high quality Stainless Steel kettles with a thick three layer bottom – an aluminum layer is sandwiched between two stainless steel layers for superior heat dissipation. This protects against scorching and hot spots when heating a mash or boiling wort. The 15 Gallon pot is 15″ tall and 19″ in diameter. Wall thickness is 1.2 mm.
It’s great. I couldn’t be happier. It’s very wide which is perfect for boiling off volume and the width makes it very stable on the burner (which is an important feature with scalding hot liquids!) It doesn’t retain heat well thought. There is too much exposed surface area. I’m looking for other options for a mashtun/lautertun application.
I looked at the Blichmann BoilerMaker™. They have a great website – lots and lots of sizing and volume information. One of the notes is “the height to diameter ratio is the ideal 1.2 to minimize boil-off and also prevent boil-overs.” Which is an interesting point, but I’m not looking for a boil kettle.
For a mashtun, my Rubbermaid “Gott” coolers have served me well for years. I have come to appreciate the height-width ratio and their ability to retain heat. This started me looking for a kettle that was taller than wide for my mashtun. The main reason I didn’t buy the BoilerMaker™ is this comment from their website… “While the clad bottoms look impressive, they add cost, but no real benefit to the brewer.” I call B.S. on that one – I know for a fact if you are adding direct heat to a kettle without a clad bottom you get hot spots and localized scorching. The tri-clad bottom is important to me.
After kettle geometry, the next important factor is the metal the kettle is made from. I won’t go into a discussion on the suitability of aluminum kettles, just suffice it to say I won’t use one. Call it a personal preference. Stainless steel resists corrosion, is passive and can be cleaned with all the caustics or oxygenated cleaners you want.
Regarding tri-clad (tri-ply) bottoms, it turns out there are several types of wafers used in different kettles – from copper to aluminum to iron core. A quick reference of “thermal conductivity” ratings (measured in Watts per Kelvin Meter) for different metals shows one of the worst heat conductors is Stainless Steel, followed closely by Carbon Steel. Copper, not surprisingly, is the best by far.

Copper: 401 W/m*K
Aluminum: 237 W/m*K
Cast Iron: 80 W/m*K
Carbon steel: 51 W/m*K
Stainless steel: 16 W/m*K

There are some ratings for stainless steel that you will see if you go shopping online. You might see a rating of 304 SS. This refers to the alloys and additives used in the steel – 304 contains 18% chromium and 8% nickel. 316 contain’s 16% chromium, 10% nickel and 2% molybdenum. The “moly” is added to help resist corrosion to chlorides. Similarly, if you see 18/8, the first number is the amount of chromium that is contained in the stainless – 18% chromium, 8% nickel. 18/10 is 18% chromium and 10% nickel. The higher the numbers, the more corrosion resistant the material.

You will also see mm, inch and gauge ratings. These all refer to the thickness. Thinner kettles heat quicker and are easier to move and clean. Thicker kettles maintain heat, distribute heat more evenly and are more durable. It’s a matter of preference and the intended application.

gauge inches mm
16 0.063 1.6002
18 0.050 1.27
20 0.038 0.9652

I’m still looking for the perfect kettle. I think the best I can do in the 50-60qt range with a tri-clad bottom is equal height/width. A word of warning – if you’re buying online, watch out for restocking fees. Vollrath wants a 25% restocking fee! And you have to pay for return shipping. It’s an unexpected hidden hazard of online shopping.

Update – the kettle(s) I settled on are as follows:

Vollrath 47725 Intrigue 53 qt. Stock Pot.

Thanks to its 18-8 stainless steel construction and 1/4″ thick stainless steel clad aluminum base, this Vollrath 47725 Intrigue 53 qt. stock pot heats evenly and can stand up to years of heavy use.

A stock pot’s tall, narrow profile also helps preserve liquids longer and forces them to bubble up through the ingredients in the pot, maximizing flavor transfer. The Vollrath Intrigue stainless steel induction 53 qt. stock pot is NSF Listed, and oven and dishwasher safe. See Companion Items for a compatible cover.

Dimensions:
Inside Diameter: 15 5/8″
Inside Depth: 15 5/8″
Gauge: 16

Vollrath 47778 Intrigue 15 23/32″ Stainless Steel Cover with Loop Handle

This Vollrath 47778 Intrigue 15 23/32″ stainless steel pot / pan cover features a satin finished outside, and a mirror polished interior. A durable welded loop handle is comfortable to grasp and enables easy hanging. NSF Listed. See Companion Items for Intrigue cookware that this cover fits.

Dimensions:
Nominal Diameter: 15 23/32″
Gauge: 16