Making the frame for the open end
needed careful measuring and planning. The cardboard frame had to
be cut to just the right size in order to hold the balloon open. Two wires
were attac
hed
vertically and horizontally in the frame so that they crossed in the
centre. A small piece of cotton batting was placed in the centre of
the wires. When the time came for lift off, the cotton batting would
hold the fuel! The edges of the end
of the balloon were then wrapped around the frame and it was all glued
together.
The frames were all rectangles, but
there were many 
different
sizes. Each group had to work out how to get the frame into the balloon.
After the frame had been installed, the groups wanted to test the balloons. They used the heating vents in the gym floor as a source of hot air, and held the balloon in place to see if it would fill up. Some holes in the paper were found in this way, and were patched up with tissue paper and glue.
It was exciting to see the balloons fill up with air. It proved that tissue paper balloons actually could hold hot air and made success in flying them seem more possible.
As the different groups saw each other trying out things, ideas spread. Other groups tried out the testing.