Carnival was introduced by Portuguese settlers. The celebration is celebrated on each of the archipelago's nine inhabited islands. In Mindelo, São Vicente groups challenge each other for a yearly prize. It has imported various Brazilian carnival traditions. The celebration in SãoNicolau is more traditional, where established groups parade through the Ribeira Brava, gathering in the town square, although it has adopted drums, floats and costumes from Brazil. In São Nicolau three groups, Copa Cabana, Estrela Azul and Brilho Da Zona constructs a painted float using fire, newspaper for the mold, iron and steel to for structure. Carnival São Nicolau is celebrated over three days: dawn Saturday, Sunday afternoon, and Tuesday.
Three groups in São Nicolau make use of fire in the construction of what conveyance? 
a painted float