Troubleshooting Slow Heat-Up in a Kapton Heater System

https://heater-technology-guide.capitaljays.com/posts/pi-heater-basics-a-simple-guide-to-thin-flexible-heating-technology

In precision instruments, a kapton heater must deliver heat in a controlled way. It uses a resistive foil circuit laminated within polyimide film. One useful trait is custom circuit patterns. Still, hot spots can change the result