ss-blowers use a small carbon rod, about 3/16 inch in diameter,
as a flanging tool for tubes larger than about 3/8 inch diameter, and a
small iron wire or similar piece of metal for smaller tubes. In this
case the tube is heated as above described, and the rod or wire inserted
in the end at an angle and pressed against the softened part, as
indicated in Fig. 4, while the tube is rotated about its axis. For
large heavy tubes a larger carbon would be used.

=Rotation of the Tube.=--This is the fundamental manipulation in
glass-blowing, and upon it more than all else depends the uniformity and
finish of the work, and often the possibility of accomplishing the work
at all. Directions for it will be given on the assumption that the
reader is right-handed; if otherwise, the position of the hands is of
course reversed. The object of rotation is to insure even heating of the
whole circumference of the tube at the point of attack, to equalize the
effect of gravity on the hot glass and prevent it from falling out of
shape when soft, and to keep the parts of the tube on each side of the
heated portion in the same straight line.

In rotating the tube, both hands must be used, so that the two ends may
revolve at the same rate and the glass in the hot part not be twisted.
The rotation is performed by the thumb and first finger of each hand,
the other fingers serving to support the tube. As it is almost always
necessary to follow rotating and heating a tube by blowing it, the hands
should be so placed that it will be easy to bring the right-hand end up
to the mouth without shifting the hold on the glass. For this reason the
left hand grasps the glass with the palm down, and the right hand with
the palm turned toward the left. If there is any choice, the longer and
heavier part of the tube is usually given to the left hand, and it is
planned to blow into the shorter end. This is because it is easier to
support the tube with the hand which has the palm down. This support is
accomplished by bending the hand at the wrist so that it points slightly
downward, and then curling the second, third and little fingers in under
the tube, which is held between them and the palm. This support should
be loose enough so that the thumb and first finger can easily cause the
tube to rotate regularly on its axis, but firm enough to carry all the
weight of the tube, leaving the thumb and first finger nothing to do but
rotate it. The hand must be so turned,