cut metal(copper) 
cut into small pieces 
punch 
use drilling bit to remove sharp part 
sanding direction 
opaque enamel is easy to burn black 
first, burn top glaze(fire burns from below). then use sand paper to polish oxide layer and wipe with alchohol to remove oil.(if not, enamel will not stick to metal横二竖二). second, burn bottom enamel(fire burns from above, burns enamel directly)
if you use gum(mixed in bottom enamel) to burn two sides together, the bottom enamel may fall off .横二竖一
try to use transparent enamel as bottom enamel
