Thermal Mass

Thermal mass is the capacity of an object to store thermal energy. It's a function of the object's mass and specific heat capacity. A heavier object made of material that stores energy well (like cast iron) has more thermal mass than a lighter object (like a thin stainless steel pan).

In searing, thermal mass determines how much the pan's temperature drops when a cold steak makes contact. A 12-inch Lodge cast iron skillet weighs 8 pounds and stores an enormous amount of thermal energy at 650°F. When a 1-pound room-temp steak hits it, the pan cools by about 80°F (to 570°F). A thin stainless pan might cool by 250°F — dropping to 400°F, which is far below optimal searing temperature.

Why this matters: The Maillard reaction rate roughly doubles every 18°F. A pan that maintains 570°F produces crust roughly 8x faster than one that drops to 400°F. This is the primary reason cast iron outperforms thin pans for searing — not thermal conductivity (cast iron's conductivity is actually poor), but thermal mass.

Carbon steel vs. cast iron: Carbon steel pans are thinner and lighter but made of a similar material. They have less thermal mass and will cool more when a steak is added. However, they recover temperature faster because they're thinner. For searing, cast iron's mass advantage generally wins.

Practical tip: Preheat cast iron for at least 5 minutes on maximum heat. The mass needs time to fully absorb energy. Under-preheating wastes cast iron's main advantage.