----Cradle of the Sun Tips

Glass Cutting - Soldering - Leading - Glass Creation/Selection - Tools Supplies/Equipment - Puttying- Misc

Glass Creation and Selection:

The main component of glass is quartz sand. Alone it has too high a melting point so other materials are added. These are soda, lime and potash. At this point the mixture, melted at a very high temperature, is clear. Metal compounds are added to create various colors.

There are two major divisions of glass according to the method of manufacture. They are Antique or blown glass and rolled glass.

Antique glass is so called because it is the method used to make glass since the Middle Ages. Through several steps, a long cylinder is blown, the ends opened up and the cylinder is then scored with a cutter down the side. The piece is then reheated in a furnace and the cylinder opened and flattened out creating a sheet of glass which is then gradually cooled in order to anneal the glass. Antique glass is usually varying slightly in thickness and has happy accidents such as varying sized bubbles and other irregularities which addd interest to the glass. Normally antique glass will have striations on the surface which adds life to the glass making it vibrant in natural light.

Flashed glass is a varient of blown glass that has had the gather -which would be a pale tint or clear- dipped into molten glass of a darker color. The resultant sheet will have a paper-thin layer of color (the flash side) on a thicker base (the clear or pale tint side). Flashed glass can be sandblasted or acid etched on the flash side removing the color and exposing the base creating a complex design in a simply shaped piece of glass. This was especially helpful back in the early Middle Ages before the invention of glass cutters.

GNA or FNA (German or French New or Near Antique) glass is made in the Vertical Draw Method. Molten glass is pulled vertically through a slit in a refractory block that's floating on the molten glass. The annealing lehr is mounted vertically over the draw chamber. This glass is ment to simulate antique glass. There are striations on the surface that are mechanically imparted to the glass. There are no bubbles in the glass normally. The limitation to GNA/FNA glass is the limited color range. The are about 25 colors of GNA glass (none of which are "hot" colors) but hundreds of shades of full antique glass. Return to top:

Rolled glass is made by putting molten glass in a hopper that feeds into a pair of rollers. As the flatten the glass comes out the rollers it is laid on a tray moving forward under the rollers at the same rate as the glass is comes through the rollers. (Picture) The sheet is then placed into an annealing lehr. If the bottom roller has a pattern on its surface, the negative of that pattern will be transfered to the bottom side of the rolled glass. One side of the glass is always kept smooth for the glass cutting wheel to be able to roll and score the glass. Exceptions would be drapery glass or Job glass which need to be cut with a glass cutting saw.

I divide rolled glass into a couple of classifications based on how the light is transmitted through the glass. I define cathedral glass as rolled glass that needs light coming through the glass to your eye in order to be able to readily see the color of the glass. At the other end of the scale is opalescent glass which is more opaque than cathedral. It not only glows with transmitted light but also shows color from reflected light. There are many degrees of variation between one extreme and the other resulting is varying degrees of wispy glass.

In selecting glass, I try to avoid having all the glass in a panel be opalescent. I want to maintain a greater feeling of transparency and avoid having your eye stop at the plane of the glass. I try to avoid having the panel look like a wall painting. I want the fact that the panel is made of glass to be obvious. Therefore if I'm using opalescent glass I confine it to areas that would be best represented by a more solid feel such as mountains, plants, the main design in a geometric design or a border. The more ethereal parts of the panel I would use non-opalescent glass. These would includes areas representing sky, water, background and so forth. An instance where all glass should be opalescent would be in the case of a lampshade. You should try to avoid having "hot spots" where the bulb would show through. Other than that, have fun.Return to top: