Glass is a unique materiel that presents many possibilities to designers and engineers, as well as to artists.  Many of the unique possibilities that come with this material often are coupled with a large set of limitations.  Part of truly being able to control this material, for both artists and engineers, is to understand, the often complex processes involved in the heating, forming, and cooling of this material.

· Strain point:  The most crucial part of the annealing process, this is right below the annealing point, when the molecules can no longer re-arrange. This is when the majority of stresses due to improper cooling will be reintroduced to the glass.  With thicker glass this usually requires long soak times to make sure that all parts of the glass are cooling at the same rate.

· Annealing point: Relieves stresses induced by the shaping/forming processes.  There is inevitable stress due to the rapid and often uneven heating and cooling processes when forming glass at the torch.   This coupled with mechanical stresses; due to sharp angles in your form, or inconsistent thicknesses will be enough to crack your piece if it is not properly annealed. (lead into Polariscope  demo)

· Softening point:  When the glass has a viscosity high enough to prevent deformation under its own weight. (very dull red)

· Working Range: The variety of viscosities ranging from very stiff to very fluid.  Minute differences in viscosity caused by slight temperature changes give the artist a broad range of working properties. (dull red - bright yellow)

· Melting point:  This is the point at which the glass is very fluid, and moving almost uncontrollably fast.  The closer you are to the melting point, glass becomes more fluid, and there is a higher the surface tension. (bright yellow-white)

Physical Properties involved in Lampworking:

· Physical properties involved in the forming of molten glass: Gravity and Surface tension.

· Proper Spinning technique:  necessary to evenly distribute the effects of gravity on the piece.

· Heat Base:  an even distribution of heat, allows for symmetrical blowing and forming. If glass is allowed to cool slightly before forming, the heat will start to even out, allowing for more balanced forms.

Demonstration of Gravity and surface tension:

-Heat the end of a glass rod while rotating; watch as the glass rod begins to ball up into a spherical shape due to surface tension.

-Notice while the glass is molten, if you stop spinning the glass will droop down due to gravity.

-These are the most fundamental properties involved in forming glass at the torch.

Demonstration of condensing/stretching:

Condensing:

While spinning evenly and heating the middle of a rod, you can start to push your hands towards one another, and the rod should start to bulge out into a round form.  If you continue to push you hands together, the bulge will start to form into a more disk shaped form.  This very common form in lampworking is called a "Maria".  An even heat base that results from consistent spinning is the most important force in forming a perfectly shaped Maria.

Stretching:

The most dramatic example of stretching is pulling large gathers into small size stringers.  After pulling several stringers, we often have a small contest between the several groups participating in the demo.  Each group chooses one person to take a hot gather and stretch it as far as they can.  Because we are using a high expansion glass (104 C.T.E.) it stays malleable for quite some time, which allows for impressively long pulls.