We have many, many discussions here about pan evenness, but short of FLIR thermographic imagery, how do we *really* assess and compare evenness? Using IR and contact thermometers will drive you crazy, and there is no easy way to depict and appreciate the result. Comparing how a strip of bacon or long tri-tip steak cooks sorta/kinda works, but if I say X, how does some other Hound replicate my result or see how *their* pan compares? Anecdotal reporting about evenness isn't very helpful, frankly.
But there is a basic thermographic tool that anyone can do at home: a scorchprint. The first ones I saw were the work of Dave Arnold, mastermind of Cooks Issues. Dave demonstrated quite powerfully how uneven cast iron pans can be, and how uneven induction hobs in general can be. See, http://www.cookingissues.com/2010/02/...
Basically, a scorchprint requires that something, usually flour, but sometimes parchment rounds or other things, be placed in a pan. The pan is then heated, and a visual record is made of where the pan browns, burns and where it doesn't. The resulting photos (or crispy parchment) can be graphic, enduring proof that Pan A is even or that Pan B hot-spots on Hob C. I do a fair number of scorchprints every month in evaluating and reviewing pans and appliances.
Of what value is this to a home cook? Well, we all want the best pan within our budgets, and even pans are better pans. And, it turns out that any given pan may be more or less even on one type of home hob than on another. For example, a Demeyere Proline 5* may be less even on induction, but more even on gas, than is a Fissler Original Profi skillet. See, accompanying photos. Why would you risk wasting your money on a pan that won't be even on your own cooktop?
I encourage anyone who is interested in assessing evenness for themselves to learn to do scorchprinting. And I want to suggest a way of doing it that hopefully will make reporting of results here on Chowhound more useful for more users; if we all do it in a similar way, it will facilitate meaningful discussions, and reduce battles of anecdote and bare opinion.
Here's the way I suggest:
1. Lightly grease the pan with shortening. By "lightly" I mean only slightly more than you would wipe onto a cast iron pan to season. Make sure it's evenly and smoothly coated and evenly spread on both floor and sidewalls. Greasing is important if you want to see how the sidewalls do or don't heat, or whether your pan also suffers from "Ring of Fire" unevenness.
2. Dust the whole interior with flour. In fact you can dump in a large quantity of flour into the pan. It will look uneven, because it is.
3. Tipping the pan, shake it to move the loose flour onto all the greased surfaces. A well-placed rap with a wooden spoon will knock excess flour loose and allow you to get a very uniform coating. A thin uniform coating is important because the scorchprint needs to accurately reflect differences in browning--uneven flour can result in bad imagery and ambiguous conclusions.
4. Before putting the pan on the heat, invert it over the trash and rap it hard a couple times with the wooden spoon. If the coating looks uneven, repeat Steps 2-4.
5. I like to place the pan on a cold hob and set a low heat. I think it's a fairer test to preheat the pan this way, since many pans are so thick, and modern hobs are so powerful, you can create a hotspot scorch in just about anything by blasting it with too much heat too fast. Make sure you take care to perfectly center the pan. I keep the pan on that low heat until I smell the flour toasting. This gives the pan a chance to already have some heat out at the edges and sidewalls.
6. When I smell the flour, I boost the heat to medium or medium high. On induction, I like a setting like 65/100 or 6/10.
7. Then just watch and/or take photos. Remove the pan from the heat before the flour turns true black, and DO NOT QUENCH THE PAN IN WATER--allow it to cool on a trivet.
Following this process has given me consistent results. I hope you try scorchprinting, and I hope you find this useful.