Lodge Dutch Oven
A year or so ago I bought a Lodge 6 quart Dutch Over. It’s a great pot and I’ve been very happy with it.
However, I’m curious about one of its features. There are 3 rectangular “bumps” or cleats on the bottom of the lid where it touches the upper edge of the pot. They are spaced 120 degrees apart around the circumference of the lid (see photo). There obvious purpose is to lift the lid off the pot allowing a gap between the lid and pot.
It would seem to me that you would want to seal the lid as tightly as possible to the pot to avoid the built up steam from escaping rather than condensing on the bottom of the lid and dripping back into the pot. In fact, a lot of recipes recommend placing a sheet of aluminum foil between the lid and pot to ensure a tight seal.
This design feature seems to ensure that the steam will in fact escape. Is this a safety feature to avoid an ad hoc pressure cooker or is there some other reason for it.
I contacted Lodge and asked them but never received a reply.
I checked a couple brands of enamel CI at TJMaxx. Chantal had the 3 bumps, almost identical to your picture. LC also had the 3 bumps, though they were more subtle. Definitely meant to be a stable 3 point support. Even if the fit was perfect when cold, the pot and/or lid could distort slightly when hot.
paulj’s correct. I should have pointed out that it is an enameled pot. The black surface shown on the lid is some sort of primer or undercoat. It’s not bare iron, so I don’t think rust is an issue.
I think Chemicalkinetics might be on to something. Making the lid rest on the three cleats assures that it won’t wobble when placed on the pot. This would compensate for a slight concave or convex surface of the lid bottom rim, the pot upper rim, or both due to the imprecise nature of the casting process.
Three is a key number. If there were four cleats, you could get a condition where only two of them touched the pot’s rim and the lid would wobble around their axis like a chair with one short leg. Three legged stools never wobble and can’t because of the design. The seat may not be parallel to the surface the stool is resting on, but it won’t wobble.
I've read threads where people worry about the LC or Staub lids rocking or not fitting perfectly. Some blame it on 'seconds', but I suspect perfect fit is not possible with this method of manufacturing.
Also, you don't need an air tight fit for dutch oven cooking. That's for pressure cookers with rubber gaskets. There are traditional methods that seal the lid with a strip of dough, but those work with really low heat applications.
Harold McGee advocates braising with the lid ajar, so the liquid stays below boiling. I often lift the lid off a dutch over or other pot and find the liquid bubbling away (which stops within a few seconds).
I agree with Piggin. Aside the from the rust thing he mentioned, I also believe it is to protect the seasoning surface along the edge. If you have the lid perfectly flat on the pot lid, then they will rub against each other all the time and the seasoning will get lost very fast and will easily get rusted. These tabs will ensure only the tabs areas are in contact.
Alternatively, it could be because it is too difficult to make a cast iron cookware completely perfect straight. Therefore, if you try, you will likely make a lid which waggle, so you make a three-legged tab instead. Much like the ancient Chinese Ding:
From an engineering view, a three leg design is easier than a four leg design, which in turn is easier than a circular leg design:
I cook a lot with my campfire dutch ovens and have never had a problem of too much steam getting out of the oven. These things are great! I would venture that the raised edges are to keep moisture out of the oven to prevent rust when they are stored with the lids on. Just having that simple gap would let any moisture evaporate out keeping it dry.