It's cold and draughty, but they need a big space to work and a big door to get the finished lanterns out and the owners have provided this free of charge.
In line with this year's theme, "creatures of the sea", gigantic sea-horses, clams, shells and other sea creatures are taking skeletal shape.
Bamboo is used for the structure with cane for the contour lines, held together with masking tape so they are strong and light and safe, Katrina says.
For safety, up to 10 candles wired inside the structures have to be a certain distance from the cane and covering tissue paper which acts as a diffuser.
Holes are left above the candles for chimneys and small doors in the sides allow them to be lit.
It means the structure has to be part of the design as the cane is seen as a shadow.
It's like drawing in 3-D with cane, Karan says.
The artists won't see the full effect of their work until the carnival procession when the enormous lanterns will be lit for the first time.
