"Simply hold it steady, for now," he explained, collecting the mortar full of the ground, black powder and a brightly coloured paper packet of something. He handed the latter to her.

"When I am not pouring, add the contents of that. Enough to cover the surface."

The said contents seemed to be some brightly reflective metal powder.

"...Like a layer cake," he added offhandedly. Perhaps thinking about something more pleasantly mundane would keep the young lady calm.