One
advantage of fusing over leading or copper foiling is that shapes
impossible to cut as a single piece can be made from multiple pieces.
However these joints often show up in the finished work.
You
are always more likely to have the joints show when the cut coloured
glass is on the bottom. The infra-red heat of the kiln elements goes
through the clear glass to the coloured below, allowing it to soften
first. As the glass underneath softens and pulls in, it allows the
top glass to sink into the space. Upon cooling the seam is kept open
even sometimes showing a clear line at the joints.
Putting
the clear as the base and the jointed pieces on the top has a better
chance of having the joints fully fuse together. There is no glass
above to spread the pieces apart.
When
you need the joints to be concealed, you can put a line of powder the
same colour of glass over the joint. This line should be slightly
rounded above the surface along the joint to account for the
reduction in volume as it fuses. When it is two colours meeting,
using powder of the same colour as the darker glass is most
successful.
Fusing
to a contour fuse for 10 minutes is normally hot enough, but taking
the piece to a flat fuse – again for 10 mins - will certainly be
enough to fully melt the powder into the joint.
