jerryc41 Loc: Catskill Mts of NY

I don't like mysteries. Since getting a new stove, I have a mystery. The stove is one of those black, flattop units. Unfortunately, not all of my pots have a perfectly flat bottom. They have a raised center, as if someone hit them from the inside with a ball peen hammer. When I put a pot of water on to boil, the pot will begin to rock back and forth rhythmically at the rate of several times a second. It will start doing this as soon as the water gets hot. It doesn't have to be boiling. I can stop it, but it will start up again. Why does this happen?

A mystery I solved - Did you ever notice the smell of rain? Occasionally, when it begins to rain, I know it's raining because I can smell it. I did some research and discovered that the smell is called petrichor, a fairly new term.

https://en.wikipedia.org/wiki/Petrichor

dpullum Loc: Tampa Florida

Jerry said..."It will start doing this as soon as the water gets hot. It doesn't have to be boiling."
Jerry, it may be a supernatural event... the spirit of your grandmother who used to cook for you as a child. Oh! My god, that was a Republican answer... anti-science.

The low side heats faster than the elevated side, but the water is at the same level. As the hot side heats and expands it shifts more water to the hi side so as to maintain water level. in so doing the hi side water is denser and so heaver and the pan rocks to the heavy side. This theory would not work if the elevation difference was great.

Science sadly takes the romantic supernatural away from describing an event ... as when you were young and told that sex was a religious experience and not to be practice with Sara down the street who was the spiritual awakening partner to many of the boys. Or in the case of freshly falling rain the smell .. better-called perfume aroma, Petrichor... Well, to know does not diminish the experience.... tho the research and reading of it was an experience in its self. Caution... enjoy the aroma without recalling details of the research is advisable.

jerryc41 Loc: Catskill Mts of NY

Excellent answer, and I'm ashamed I didn't think of that. It makes perfect sense.

As for your supernatural idea, I thought this phenomenon might be because my house is built over the burial ground of aliens who arrived here from another galaxy several thousand years ago.

dpullum Loc: Tampa Florida

I smile

Architect1776 Loc: In my mind

Interesting on the rain. Not sure how that works in desolate desert areas where there is a smell though but it is interesting to know why one can smell the rain.

tommy2 Loc: Fort Worth, Texas

Another characteristic of the fittest who survived:
"Some scientists believe that humans appreciate the rain scent because ancestors may have relied on rainy weather for survival."

DirtFarmer Loc: Escaped from the NYC area, back to MA

If your pots have a bump on the bottom on which they can rock, turn them over and hit the bump with a hammer hard enough to make the bump an indent. That way they won't rock back and forth.

speters Loc: Grangeville/Idaho

I've had one of those over 40 years ago and I liked it and was impressed with it. I could put my hand on the stove and it would not burn, but the pot next to it would heat up, interestingly, an empty pot would not heat up as well, only the ones with stuff and or liquid in it would!

newtoyou Loc: Eastport

Cast iron and other metals get larger as they heat.
The center will pucker as bottom expands.
Modern cookware works on a glass top stove.
Made to do so.
DO NOT TRY to beat a cast iron pan flat.
It may crack.
Good excuse to get new cookware.
As to why it happens?
Unevenn heat.
And air expands faster than water. Weight shifts around a center.

Bill

pmorin Loc: Huntington Beach, Palm Springs

I would use a wood block centered on the convex surface and the hit it dead center of the pot. Otherwise you may end up with a noticeable dent in the bottom of the pot. Or use a rubber hammer with a 2” face.

bobmcculloch Loc: NYC, NY

I've been told the bump is the result of heating pots and pans too fast, eventually the metal changes shape, no cure, just prevention, preheat slowly BTW most amusing on a coffee pot, rock and perk at the same time.

geezer76 Loc: Prineville, Oregon

Confused!! What part of Photography is this subject?????

AirWalter Loc: Tipp City, Ohio

The part about pots and pans. What's not to understand since this is the section used for things that are not about photography!

olddutch Loc: Beloit, Wisconsin

I believe this happens because with the pucker factor most pilots are familiar with this.

Papa Joe Loc: Midwest U.S.

Hi Jerry,
I have the same 'ghost' in my kitchen. Actually, it only takes place with my aluminum kettles, so little by little I've purchased replacements to the heavier, 'no stick' type and they behave nicely. As an 'extra', I have learned since we began using the 'black, flat' electric stove top , that keeping the bottoms of the pots clean is just as critical as cleaning the insides. Prevents a lot of unnecessary stove-top cleaning. (Temporary help: Grasp the dancing kettle firmly by handles on each side and bear-down firmly. Sometimes stops the dance by 'popping' the bulging bottom into a flatter shape!)
Good Luck,
Papa Joe