The volcano strikes an ominous presence on the horizon - one of countless sleeping giants in Iceland that might one day stir, sending torrents of fire, rock andash raining down.
Afterwards Mr Cai and his assistants damp out the fire using long poles tipped with sponges, and then smudge the lines of ash so that the portrait looks like a huge charcoal drawing on the wall of the museum's reception hall.
"I am advised that the fire is contained and we hope that there will be significant improvement in the situation with smoke andash in the next few days, although the site may not be able to be cleaned up for some weeks, " he said.