Predicting when food will be "just done" often feels like more of an art than a science. When you double the thickness of steak, does it take twice as long to finish? Or perhaps four times as long, to cook? If it takes an hour to bake a chicken breast in a 350F oven, will it take 30 minutes or 45 minutes at 450F? Does weight matter more than thickness, or vice versa?

The answer is simple- it depends. It depends on three important factors:

• Thermal diffusivity of the food
• Shape of the food
• Evaporative cooling

In previous articles we've demonstrated how evaporation may cool food so effectively, the temperature stops rising entirely for hours at a time. Or how doneness is really a surrogate for residual moisture content.

The interaction between all three effects is NOT simple, and does not lend itself to simple prescriptions. This article will discuss the first contribution, thermal conductivity.

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In the practice of all-things barbecue, we appreciate the support and conversations with Meathead at AmazingRibs.com, Sterling at BigPoppaSmokers, along with numerous competition pitmasters and backyard chefs.