Tempering

Bikes frames can be made from various materials these days - aluminum, steel, titanium, carbon. Steel is often prized by cyclists because it can be designed to balance various properties - strength, rigidity, flexibility.

Steel's properties are influenced by how it is cooled and then subsequently heat treated. Often, the first step in hardening the material is to cool the hot steel quickly (e.g. quenching in an oil bath). This creates a steel which is hard, but is also brittle and fractures easily. Essentially, the rapid cooling does not let the ingredients (iron, carbon, etc.) time to settle into comfortable positions. The atoms are 'frozen' into small imperfect crystalline structures. The material is full of stresses and defects. At this point the rapid cooling has produced a significantly harder steel - but its characteristics are not ideal. Though it's surface is tougher, the byproduct is weaker in many respects.

Tempering, however, can significantly improve the properties. In this step the quenched steel is put into an oven and baked slowly for a long period of time. The temperature is not nearly as high as before so the steel retains its hardness and fine crystalline arrangement, but the lower temperature allows the internal structures to begin to "heal". Defects begin to resolve. Fractured areas are filled. Much of the crystalline structure begins to reorganize and reform into more efficient arrangements. The steel is now allowed to cool more slowly. The new crystals are stronger and more elastic. The final product is more flexible - it has the ability to shoulder greater loads without breaking and yet retains the hardness it's acquired.

I feel like I was hardened by the loss last Winter, and since then I've been in the tempering stage - softening up and becoming more flexible all the time.