When should removal of the head riser begin?

The removal of the head riser should begin when the tips have started to turn grey because this color change indicates that the molten metal has begun to solidify and is in a suitable condition for riser removal. It is essential to wait for this visual cue, as it signifies that the weld metal has cooled enough to maintain structural integrity but is still soft enough for the riser to be removed without creating additional cracking or damage.

Timing this process is crucial; if removal occurs too soon, while the metal remains molten, it could lead to defects in the weld due to disturbance in the molten metal. Conversely, waiting too long could result in complications related to excess heat retention or rigidity of the final joint.

Thus, the color change serves as a reliable indicator for the right moment to initiate the removal, ensuring that the quality of the weld is maintained while successfully discarding unnecessary material.