Hello! That’s a great question. I just saw a demo video on the internet where the person uses fingers to touch and feel the tackiness / readiness. 😵‍💫 The wait is also for urushi to settle down (self-leveling) so you will have a flattened and prestine surface to receive the gold powder. The wait is about 15-20 mins in the muro. (Temperature and humidity controlled). When the urushi surface looks even with no hint of brush marks or bumps, then it is ready for powdering.