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Cookware with a flat pan

Pan to burner size mismatch

Why do you need to match your cookware to the burner size?  I received a great question recently about the standard recommendation stating your pan size should match the burner or heater size of the cooktop.

“HI, I just bought new double oven range with the ceramic top.  It has a ” bowtie ” between two burners.  Measures top to bottom burner 17 1/2” and 7″ side to side.  Because of the bowtie I would like to use a griddle, but the Manufacturer say’s you should never go beyond 1 inch of the burners.  If I do, what could happen to my stovetop(crack)?  I saw griddle that measures 21 by 12 inches.  The overlap is there.  Can I use this griddle safely with out worries of my ceramic stove top?  Thank you!”

First off, no worries about cracking cooktops with a mismatch, at least not right away.  Let’s look at the way the burner and pan orient themselves in my simple sketch below.

Example cooktop with pan

Example cooktop with pan

If you look at the cross-section of the pan on the glass, over the heating element, you see how the pan is perfectly flat and rests evenly on the glass!  This is great…but not always reality.  Perfectly flat allows for full contact of the hot glass and the cookware.  For a radiant cooktop, this is important as a good percentage of the heat transfer is by conduction (contact) from the hot glass to the pan.  For induction, this is not so critical.

Cooktop with FLAT Pan & too large

Cooktop with FLAT pan & too large

A full contact surface between the pan and the glass does two things.  First, what your are cooking heats faster!  Second, the heat leaving the glass to go into the pan keeps the ceramic glass panel cooler.  (by cool, I mean below 1,100ºF /600ºC).  This is the temperature the ceramic glass can begin to age and then eventually crack.

Cooktop with "poor" contact and too large pan

Cooktop with “poor” contact and too large pan

Here is a picture of a poor contact surface between pan and glass-ceramic.  You can see the “too large pan” has contact points outside the heater perimeter below.  So, the fast heat transfer via conduction is not there and the ceramic glass just keeps getting hot.  If the thermal limiter below the glass catches the high temperature, it will cycle it off and on more often.  This makes cooking slower you frustrated.  The limiter is only in one place under the glass, so it’s probably not catching the hottest spot, and in those areas, the glass can age more quickly leading to an eventual break.

Unless the cookware is really warped and uneven, this process will take quite a bit of time to age the glass.  The immediate problem is the poor cooking speed!

Obviously with a bowtie type heater, cookware is seldom a direct match.  Just be sure to look for cookware that is really flat.  Some cheaper cookware will actually bend when it gets hot. Best is higher quality cookware with a very slight concave surface.  As this material gets hotter it will bow to flat.

So if your cookware doesn’t match in size, at least make sure it’s flat.

Keep in mind, the pan (and your food) will not be evenly heated in this scenario…but you probably already figured that out.

Hope this helps!

Ted

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2 Responses to “Pan to burner size mismatch”

  1. Agnes March 7, 2016 at 12:05 am #

    This is very informative explanation of why the size mismatch or gap between the pot and cooktop surface may not be the best idea. Thank you!
    Unfortunately, “my” (rental) cooktop has only 8 in and 9 in diameter burners. Since most of my pots are one-person sized, a few have bottoms smaller than 8 in, and only one pan is large enough for 9 in burner. So I either mismatch things, or don’t have enough burners to use at the same time… Oh, yes, and my favorite cast iron pan is small AND has a ring on the bottom 😉
    So here is the question: would some sort of heat diffuser plate help? Would it prevent the glass-ceramic from overheating?

    • Ted Wegert March 16, 2016 at 1:43 am #

      Good question and I understand the lack of correct pan sizes for a rental. Generally, I would say a heat diffuser is not worth the effort, but honestly in your case with the supportive ring around the pan you are missing the direct pan to glass contact. With the heat diffuser the problem is the material used. If it is a soft metal like copper, you run the risk of that soft metal rubbing off on the glass. Efficient heating, or remotely fast in this case, can only come with good full surface contact of the diffuser to the glass and the diffuser to the cast iron pan. So, it would have to sit nicely inside this channel. Might be difficult to find such a match and have adequate metal hardness the diffuser. I’m not so familiar with diffusers though. I will look into it…

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