I found this information written in a board in the palace with the title: Ripples on Steel: The art of watered steel blade
The watering effect on blade, or jauhar, as it is called in India and Persia, shows a pattern of dark undulating lines, waves or knot like nodules on the entire length of the blade, thus revealing a beauty inherent in the structure of the metal. These watered blades came to be highly prized and sought after by swordsmen all over the world. The pattern is the result of either pattern welding or the use of crucible steel, which in South India is known as wootz.
The process by which the jauhar or watered effect was transmitted to the blade was by the old Indian steel preparation method. The furnaces have been described as the pits dug in the ground and the fire was kept up by four bellows, which forced a blast of air in to the furnace and heat was applied for a considerable period. Carbon in the form of teak or bamboo charcoal was then mixed with iron, and the mixture was put through the heating process once again till the iron became partly re-carbonized. It was afterwards allowed to cool very slowly, resulting in a crystalline effect in the metal which showed up as watering patterns and combination of dark and light metal.
Pattern welding method: Strips of high carbon and low carbon steel were welded in to one bar which were then hammered, twisted, folded, cut and put through a complex forging process. This produced a strong blade with a patterned surface showing strands of light and dark metal.