Glass is a unique material 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.
The most crucial part of the annealing process. The strain point 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.
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).
When the glass has a viscosity high enough to prevent deformation under its own weight (very dull red).
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).
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 has a higher surface tension (bright yellow – white).
Physical Properties Involved in Lampworking
Gravity and Surface Tension
Physical properties involved in the forming of molten glass.
Proper Spinning Technique
Necessary to evenly distribute the effects of gravity on the piece.
An even distribution of heat. Heat base 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.