Glass is an ancient material. Its historical origins go back more than 5,000 years to early Egypt, but I shall confine these remarks to very recent developments in glass technology -- to those modern products of the research chemist's crucible which we may appropriately call today's glass.

Today's glass is as different from the glass of fifty years ago as the radar is different from the wig-wag signaling of the 19th century. The uses of yesterday's glass were limited because the glassmaker did not know the secret of controlling its color, its strength, its resistance to the passage of electricity, and its other properties. Today practically every characteristic of glass is alterable at will by the research chemist. Glass is no longer just a substance for windows, lamp chimneys, beakers and tumblers, and other traditional uses. It has become a widely versatile material, an essential material, on which we depend to give safety, ease, convenience, and comfort to our way of living.

Because its applications are so many and so varied, today's glass is, in reality, thousands of glasses, each with one or more of its properties enhanced to adapt it for a specific use.

Today's glass in all its infinite variety and uses is determined by the chemicals that are melted together to make it, by the forms into which it is shaped, and by the temperature changes these forms are subsequently made to undergo. In fact, today's glass is whatever the glass research chemist and his co-workers in physics and engineering will it to be.

It is well known of course, that ordinary white light, such as sunlight, is a blend of all the colors of the rainbow, ranging from red to violet. Certain types of modern glass will select particular radiations specified by the chemist, and transmit only these. For example, if our chemist wishes objects to appear a pyre red, today's glass will eliminate the orange, yellow, green, blue, indigo, and violet, and pass undiluted red. If a wholly yellow world is wanted, or a green world, or a blue world, today's glass will halt the unwanted colors and give the pure tint that is desired. The chemist has made this modern colored glass serve wherever color is desired. It furnishes effective traffic signals on land and sea and in the air -- and provides the color by night for the "Broadways" and "Main Streets" throughout the world.

Another modern glass will halt all radiations which are visible to the eye, and pass only the heat rays. The infra-red glass will send and receive a beacon ray that can neither be seen by the eye nor intercepted by radio. Still another glass is opaque to both light and heat but transparent to those high-frequency vibrations which we designate as ultra-violet. This ultra-violet glass transmits radiation to sterilize our food, to produce suntan, and to make visible to the airplane pilot at night the luminous dials of his instrument board.

Enclosed within a shield of glass, the x-ray tubes of our hospitals cannot send forth their rays except through the small uncovered window of another type of glass that forms the tube itself. Glass thus confines the searching and healing x-rays to the path desired by the operator without danger of excessive exposure to himself.

Because of its high resistance to the passage of electricity and its low power loss, glass is a vital part of every radio, television set, and radar installation. This modern glass, endowed by science with enhanced electrical properties, insures the fidelity of music and speech as transmitted by telephone and radio.

Sometimes the prime requirement, after transparency, is strength. We desire that the windshields of our automobiles, the goggles for our eyes, the windows for our fighting tanks, and the crystals for our watches, be capable of standing hard knocks. By a process similar to that by which steel is hardened, glass is tempered and made resistant even against bullets.

Sometimes weakness is desired. A device used during the war to attach extra fuel tanks to the fighter airplanes was a sharp elbow of glass tubing. The glass was purposely made weak so that it would break at the first tug and thus relieve the plane of the now empty and useless receptacle.

Today's glass expands with heat and contracts with cold, little or much, according to the formula of the glass research chemist. The manufacturer wants a pipe line to carry hot and cold chemicals, brines, or juices through some industrial process. The housewife desires utensils in which she can prepare food and at the same time witness pies or bread in process of baking, potatoes boiling, coffee percolating, eggs or meat frying. One type of glass, with low expansion on heating, satisfies these desires. Another type of glass goes to the opposite extreme, and with an expansion equal to that of iron, meets the requirements of the vacuum tube in which glass and iron must be tightly sealed together.

One form of modern glass has the texture of angle-food cake. it starts out as quite normal looking glass, is then ground to a flour like consistency, and after being mixed with carbon soot the glass dough is baked at a high temperature. As it bakes, the glass rises under the influence of millions of tiny gas bubbles, and as it cools the glass hardens into a texture so light that it will float on water. This angel-food glass is used as a heat insulating material for refrigerator cars and cold storage rooms.

Glass is being spun into fibers finer than the thread of the silk worm's cocoon. These fibers are being twisted into yarns. and woven into cloth. The resulting glass textiles are used to make fireproof curtains, insulation for electrical transmission wires, and even comforters, quilts, and sleeping bags.

Today's most remarkable glass a monument to the ingenuity and skill of the glass research chemist, is of pure silica. Like the beautiful luna moth which emerges from the lowly caterpillar, this glass is an end result of evolution, a creation brought into being by the chemist as an otherwise useless member of the glass family is destroyed.

The glass begins as any normal glass -- a mixture of molten oxides including sand. Sand, I may add, is the oxide of silicon. In this molten stage of the mixture the glassmaker can fabricate any vessel, beaker, flask, tube, or other useful article of glass for the laboratory, the home, or industry. Let us assume that the thing being made is a beaker, a simple glass vessel of a sort which the chemist uses constantly. As the beaker cools and becomes rigid, the chemist arrests the cooling at a chosen temperature. Gradually, under this temperature control, the oxide of silicon separates from the mixture and forms the walls for a labyrinth of invisible connecting tunnels leading through the entire thickness of the beaker, from outer surface to inner surface.

The tiny tunnels are not empty, however -- the mixture of remaining oxides fill them. Fortunately, these remaining oxides are removable, for by nature they are soluble in dilute acids and water. So now, by the simple process of immersing the beaker in a bath of weak acid and washing it with water, the contents of the tunnels are removed. The beaker, its shape maintained by the silica tunnel walls, is now reheated to a high temperature. Under this extreme heat the silica walls of the labyrinth shrink and coalesce to form a beaker only two-thirds the size of the object which began the evolutionary process.

This new glass is very extraordinary. It is clear and transparent, and readily transmits heat rays and ultra-violet radiations as well as light. It possesses strong resistance to the passage of electricity, and withstands rapid heating and cooling to a greater degree than any other glass. It can be heated red hot and then plunged into ice water. The severest temperature shock will not break or even crack it.

It has been possible in this brief talk to review only a few of the developments and applications of today's glass. Strange and fanciful as they may appear, already in the glass-research laboratories they are being supplemented by stranger and more fanciful substances that will become the glass of tomorrow.