heat treating

Today at ESSA Larry Williams helped us in heat treating the blades for the carving knives we're making. Despite what we have all been told about watching for the color change in the steel, Larry instructed us to look for other, more sophisticated signs that the steel had reached the optimum temperature. You begin to see circular shapes, like two dimensional bubbles of iron forming on the surface of the blade which are still visible after the steel is quenched and as shown below. Watching the bubbles of iron form on the surface of the blade is like watching sunspots form on the surface of the sun, but fortunately not as bright.  When the spots form, quench. Continuing to heat will cause pitting of the blade. Tomorrow the knives will be completed with handles and put to use.