In the medieval mind, swords stood above all other weapons. Knives, axes, bows, and spears were all adapted from tools for hunting or foraging. Swords stood alone because their sole purpose was fighting and killing other warriors. However, swords were also much more complicated than other weapons to make. To work effectively, a sword had to be both hard and flexible. Hard so that it would not bend when hit hard against other objects, and flexible so that it would not shatter under the same circumstances. Steel was hard but brittle. Iron was flexible but was easily beaten out of shape. The solution that medieval smiths came up with was to combine these two metals together. Thus, thin strips of both metals were combined together to make a blade that had the best of both qualities. In order to effectively weave the two metals together, though, it was essential that the temperature of each metal was carefully maintained during the creation process. The best indicator that smiths had for temperature was the color that the metal glowed — from red-hot to white-hot. In order to detect the smallest changes in temperature, the best blades were therefore made at night, when such minute changes in the glowing metal could be best detected. As a result, smiths were known to create the best blades in the dead of night, secretly working according to rituals and practices that the common folk did not understand. Thus, smiths were often seen by their medieval contemporaries to inhabit both the worlds of science, with their fine understanding of the physical properties of their materials, and magic, due to their arcane and mysterious practices.
– A few thoughts from your friend Saxo