This video is a demonstration of partial heating with a Halogen Point Heater that blocks light with a frame.
Please check the following site for more information.
Related page:
Partial heating on a piece of wood-star-shaped ★ 
Heating of wood series 1 – Spruce 
Heating of wood series 4 – Paulownia 
Heating of wood series 8 – Summary version 
Heating of wood series 5 – Agathis 
Heating of wood series 3 – Japanese cypress 
Heating of wood series 2 – Japanese cedar Sugi 
Heating of wood series 7 – Balsa