induction questions: heat distribution vs. pan size, moisture

11 years ago

I bought a single-burner induction hotplate to try out induction cooking before taking the plunge on a whole cooktop, and discovered a couple of things:

First, my giant 12" cast iron skillet heats really unevenly - hot in the middle, and literally cool enough to touch on the edges. Not entirely surprising, as I imagine the induction element is I've tried starting on the lowest setting and letting it run for a while to let the heat even out, to no avail. Again, slightly weird when compared to cooking on an electric burner of similar size for a shorter period of time. (Though I suppose electric spreads out the heat to some degree by heating the air under the pan.) So I looked into heat diffusers, and discovered that a lot of them are made of (wait for it)... cast iron!

Before plunking down a bunch of money to try an aluminum diffuser instead, I thought I'd post here for advice about getting an oversized cast iron pan to work with induction.

The second issue is that I feel like everything I cook on the new setup comes out really dry. Melted cheese tends to be soft in the middle with a dry skin on it, rather than the gooey liquid I'm used to. This might just be the ambient humidity (it's winter, and I just moved to a new place with forced air heating). I can't think of a physics-based reason why it would be the induction... but I'm not a physicist, so I thought I'd check to see if anyone else has noticed this sort of thing.

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Comments (4)

meeotch
Original Author
11 years ago
p.s. - cool article on cast iron here: http://www.cookingissues.com/2010/02/16/heavy-metal-the-science-of-cast-iron-cooking

It discusses the fact that cast iron isn't really that great of a conductor. Hence the uneven heating, and the traditional wisdom of pre-heating in the oven.
llaatt22
11 years ago
Portable induction units work best with cookery that involves liquids and a compatible smaller fry pan with some sort of cover.
You can easily see by using water with such a setup that the power is concentrated in a three or four inch "bullseye" which underlines the necessity of using some liquid to evenly spread the heat beyond the center.
A 12" cast iron pan is not going to work due to the massive radiation of such a large pan causing very high heat loss.

It's like saying:
"I'm thinking of buying a 220v electric hot plate for use with my 20" cast iron pan but first I'm going to use a large candle to see what it is like."

This post was edited by laat2 on Thu, Feb 5, 15 at 13:06
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meeotch
Original Author
11 years ago
Thanks for the reply. You got me curious, since I was under the impression that most of these units had similar sized elements - something in the 6-8" range, with the cheaper ones probably being smaller. I probably should mention that the *bottom* of the pan is actually more like 10.5".

So I took the unit apart, and measured the element at 7". I know that there are commercial-grade single-burner units that presumably have larger elements, and that some full cooktops are available with one element larger than the others. I suppose it's possible that this unit is not heating evenly across the entire element - though this seems counterintuitive to me.

Any suggestions for specific models with larger elements would be welcome. (I'm going to stick with the single-burner for now, as I'm not ready to install a full cooktop.)

Your suggestion of liquid as a diffuser makes sense. In fact, I haven't tried cooking anything that both has a lot of liquid, and takes up the entire width of the pan. My test case has been 11" quesadillas, of which I eat a remarkable number in an average week.

But my original issue remains: that is, how to evenly heat a pan of this size on an induction burner? It really seems like I ought to be able to get at least as good performance as my former electric cooktop that had similar sized (open) burners.
llaatt22
11 years ago
Your original issue does not remain.
A lot of liquid still requires a lot of energy to heat it and is just as bad as trying to cook in an oversized cast iron fry pan with no liquid when it comes to 110v portable induction units.
The size of the element doesn't matter in most cases because most of the power of a 110v portable is focused on a small circular area near the center as I have already pointed out. If you want to see for yourself buy a compatible pan, put a half inch of water in it and watch the bubbles.

In a 220v induction cooktop, the different burners or elements not only have different sizes, different power output, but even different focus for the magnetic fields. The smallest elements have fields quite similar to that of a 110v portable unit while the larger, more powerful burners have fields that cover much larger areas with a more uniform field providing less power density at the "bullseye".

If you are more interested in the higher grade portable 220v systems, www.cooktek.com is a good site.

Here is a link that might be useful: theinductionsite.com -lots of great info

This post was edited by laat2 on Thu, Feb 5, 15 at 18:23