For his indigo-dyed batik, Zahir Widadi mostly uses cotton or silk as they both absorb natural dyes really well. Beforehand, the fabric needs to be washed by soaking and lathering it with a mix of water, peanut oil, and rice straw ashes. Batik artists, natural-dyed enthusiasts, researchers, university students, fabric/textile designers, and batik collectors from all around the world frequently visited his workshop (that is set up in the front, side, and backyard of his humble abode in Pekalongan), to learn the ancient wisdom and technique of natural-dyed batik.