skillet wobbles when heated

[Jeff Marchand]

Just cleaned and seasoned a #9 Brockville Smart's.  It sits flat when cold but wobbles when it heats up.  What's up with that?  Anyone else have one that does that?  Does it get better over time, worsen, or stays the same?

[Cheryl Watson]

Yup... everytime I think I've got a Griswold #8 Large Block smooth to use... I heat it on the stove, and suddenly... spinner....
I have two of them that do it!  >:(  (or is it three?)

Cold, they sit flat as can be. Same thing everytime, no change....

I just figured the Gris 8 LB smooths don't like me... [smiley=question-marks.gif]

[Jim Glatthaar]

Cheryl, I would say "send them my way" but I really have more Griswold #8 large block logos than I could use. :o

[Ken Davis]

I'm betting it has something to do with the size of the circles that make up the large logo.

[Jeff Marchand]

Ken, can you elaborate?  It does look like the logo is where a bump is formed when it heats up.  Doesn't help that there's a bit of pitting in that area as well.
Thanks,

[Ken Davis]

The incised rings that form the circles of the logo are the "right" proportion to the skillet. They create a "weak" spot in the skillet bottom and make it warp when heated. The same logo on a different sized skillet does not have the same proportion to the skillet to cause the warp.

Does that make any sense?

[Russell Ware]

I have a Favorite Piqua #10 skillet that is dead flat cold, but spins when warmed up on heat level 4 of a glass top stove. Maybe the center was ground down a bit more, or the outer thickness increases due to the heat ring. But the center bulges down when you heat it.

[Neal Birkett]

I have noticed the significant bulging when hot is not common (much less common than outright warped), and does not seem to occur with any particular brand or style.  I have used Favorite 8s, ERIE 2nd and 3rd 6 to 11, Griswold Block 5 to 12+14, Lodge 20, Griswold Slant 8 and 9.

The Griswold Block 11 is my example that bows when heated.  But only 1 of two 11's does this to a noticable extent.  Griswold 14 and the 20 do it a little, but that is kind of expected with the size of those things.

I suspect that this is simply a combination of characteristics of the different lots of iron, thickness of the bottom of the skillet, and prior overheating abuse of said skillet.  Intense hot-spotting may contribute. 

My big Wagner 1891 absolutely does not do this, but that thing is as thick as shipplate, and just as heavy.

I would love to hear from others with more perspective on this.

[Jim Glatthaar]

I use vintage cast iron for cooking, alot.  I don't appear to have a problem with cast iron pans bowing or warping when heated.  If I do it is minor and not noticeable.  That may be because I have a gas cooktop, which can mask some of a bowing problem.  I have a commercial grade cooktop and only used low to medium heat.  I'm also careful about allowing the skillet to cool gradually before cleaning it.  I also sometimes preheat the pan in the oven.  I do have one spinner (an ebay purchase when I was just starting my collection, so that was a mistake), and it spins freely, even with the burner off.

[Roger Muse]

I have two Griswold Large Logo Block in #8 and neither of them change a bit when at cooking temp.

[C. Perry Rapier]

It could be that metal expands and contracts when heat is applied or taken away. And when you put a skillet on a burner the middle is the hottest and so the middle expands and goes down while the outside is cooler and so does not go down like the middle. So when the middle goes down the skillet is higher on the outside and thus it sticks down further than the rest of the skillet and so it spins. When it cools it goes back in place.

[Tom Neitzel]

Here's an article from a current Swedish foundry.  It is aimed at cast iron cookware on a flat, ceramic cooktop, but it does talk about the heating and warping.