Grantville Gazette - Volume V (36 page)

Two related methods of reduction by solution have been developed. In the "hot" silvering method, the ammoniacal silver nitrate solution was boiled, and the condensing steam was reduced with tartaric acid (more precisely, with Rochelle salt, the sodium-potassium salt of tartaric acid.) This deposit method is slow; it may take an hour to form a thick film. For this reason, the "hot" or "Rochelle Salt" process is favored for making "one-way" mirrors, which have a partially reflective surface (Newman, 317, 322). In the "cold" method, the reducing agent is sugar (Gregory, 158). This is also called the Brashear process.

An improvement on the basic method is to sensitize the glass so it more readily accepts the metal. This is usually done by "tinning"; treating the glass with a dilute stannous chloride solution (Newman, 15, 314).

Originally, silvering solutions were poured onto the glass. However, they can be sprayed on, instead. Typically, two jets are used, one supplying the ammoniacal silver nitrate and the other a fast-acting reducing agent such as hydroxylamine sulfate (Schiffer, p. 7).

There are alternatives to silvering, such as aluminizing, but I don't expect them to be duplicated within the near term in the 1632 universe.

Optical glass must be homogeneous. Curiously, the importance of stirring the melt, so that the ingredients were efficiently mixed, was not recognized until 1790, when Pierre-Louise Guinand pioneered the use of a refractory ceramic stirring rod. (WBE, 218). This is one of those ideas which was long in coming, but was readily implemented.

It is also important to inhibit the formation of bubbles. This can be done by the addition of a fining (degassing) agent. Several are mentioned by the
Encyclopedia Britannica
(EB): arsenic oxide, sodium nitrate, sodium chloride, sodium sulfate and sodium nitrate (EB 300).

Early glass furnaces used wood as fuel. England needed the wood for shipbuilding, and, once the English figured out how to make a coal-fired furnace, they banned further use of timber (1610-1615). The new furnaces could achieve higher temperatures, which allowed for use of higher-melting glass compositions.

There is plenty of coal in the USE, but up-timers may find it advantageous to burn natural gas instead. It is readily available in the Grantville area, it is a more intense energy source, and it facilitates manufacturing. For automated feeding, the glass must have the correct viscosity, which in turn depends on temperature. It is easier to control the temperature of a gas-fired furnace. (Douglas, 42).

Important energy savings result from the use of a regenerator. Essentially, the flue (waste) gases are used to heat a brick "checker work" (shown in Fig. 4 of the
Encyclopedia Britannica
"Industrial Glass" article, and also discussed by the 1911 EB), which in turn is used to preheat the combustion gases. Heat regeneration was first used in the 1860s and reduced fuel consumption by about 90%.

A major continuing expense for a pretwentieth-century glass factory was the pot used to hold the molten glass. In early nineteenth-century America, this pot cost about one hundred dollars, and took eight months to build from clay. It was able to resist the tremendous heat, but its life span was only eight weeks, and so the pots had to be replaced over and over again (Polak). Modern glass furnaces use highly refractory ceramics. (Different glass melts may necessitate different ceramics.) The
Encyclopedia Britannica
has two helpful comments on this point. First of all, it teaches that "clays of a high alumina-to-silica ratio, with minimal impurities," are more resistant. Secondly, it singles out the "electric-arc fusion-cast" ZAC refractory (35% zirconia, 53% alumina, 12% silica), developed in 1942.

Alumina is aluminum oxide. One major alumina ore, bauxite, is available in France and in Ireland. Please note that we aren't proposing to extract aluminum, but rather to use the bauxite, a claylike mineral, directly. A possible alternative to bauxite is kaolinite (aluminum silicate). According to the 1911 EB article on "kaolin," there is kaolinite "near Schneeberg in Saxony."

Modern glassmaking operations employ a tank furnace. The raw materials are fed in at the loading end and the molten glass is removed from the working end. These tanks can be operated continuously, while pots process glass one batch at a time, which is less efficient. The first continuous furnace was constructed by Friedrich Siemens in 1867.

While the Grantville Library provides critical information concerning both lead-alkali and borosilicate glass, the fact remains that quality control is going to be an ongoing problem. The mineral content of sands, ashes, and so forth are going to vary from source to source and even from lot to lot.

In the short term, USE glassmakers will keep careful records as to which raw materials were mixed together, in what proportions, to obtain a particular batch of glass, and the physical and chemical properties evidenced by that glass. If a particular batch does not pass muster for its intended purpose, it can be used for some less demanding task, or remelted. (A significant portion of the input to modern glass furnaces is rejected glass, called "cullet.")

The high school chemistry laboratory also should be capable of performing qualitative tests for some metals, using the standard flame and bead tests. I would expect the high school science teacher, Greg Ferrara, to know about these assays.

Grantville glass companies can make glass production more predictable by purifying the silica and the glass modifiers, so that the glassmakers know just how much of each ingredient they are adding to the melt.

Also, as the USE develops capabilities for production-scale inorganic chemical synthesis, it will be able to use alternative starting materials which are cheaper or more readily available. By way of precedent, the late eighteenth-century French government wanted to eliminate its dependence on Spain as a source of soda. (A Spanish seaweed, when burnt, provided an ash that was 20% soda.) The French offered a 2,400 livre prize, which was won by LeBlanc in 1787. LeBlanc synthesized a purified soda (sodium carbonate) from sea salt (mostly sodium chloride).

Laura Runkle has pointed out that "in order to make pharmaceuticals, the people of Grantville need stainless steel, or glass-lined vessels." ("Mente et Malleo: Practical Mineralogy and Minerals Exploration in 1632,"
Grantville Gazette
Vol. 2).

In
1632
, Greg Ferrara commented, "Sulfuric acid is about as basic for modern industry as steel" (Chap. 40). Where, exactly, do you put sulfuric acid? Clearly, you need a corrosion-resistant vessel, whether that be glass, lead, or steel. If you want to play with hydrochloric acid, you need glass, a molybdenum-rich alloy, or tantalum.

For laboratory scale chemistry, glass is clearly superior to stainless steel and various exotic metals. Not only is it corrosion-resistant, it can be made transparent, so you can observe the chemical processes as they take place. Or it can be amber-tinted, to protect photosensitive chemicals. Glass is used extensively in the bottles, graduated cylinders, beakers, flasks, pipettes, condensers, test tubes, watch glasses, burets, funnels, crucibles, and retorts of modern chemical laboratories.

Borosilicate glass, such as that sold under the trademark Pyrex, is preferred, because it is especially resistant to acids, high temperatures, and sudden changes in temperature (thermal shock).

Another form of specialty glass is optical glass. Dutch Admiral Maarten Tromp, awaiting the approach of the Spanish fleet, enviously remembers his brief experience with up-time optics: "The stunning visual clarity, featherlight weight, and exquisite craftsmanship of the binoculars had been convincing evidence of the marvels of which American artisans were capable." (
1633,
Chap. 19). King Gustav II Adolf of Sweden was equally impressed with Julie MacKay's spotting scope (
1632
, Chap. 48). And the nearsighted cavalryman Andrew Lennox appreciated his new American-made spectacles (
1632
, Chap. 16).

Like window glass, optical glass must be transparent. However, the real power of optical glass is realized when the glassware has a curved surface, creating a diverging or converging lens. Optical glass makes possible not only better spectacles and telescopes, but also microscopes. The latter is extremely important if medicine is to advance.

The preferred optical glass is a lead-alkali glass, which has a higher refractive index (a measure of the ability of the glass to alter the path of light which strikes its surface obliquely) than soda-lime glass.

Letting light escape, while keeping air from entering, is the function of the glass bulb of an incandescent light. The down-time master glassblower Hensin Hirsch is making light bulbs by hand, evacuating them using a vacuum pump scavenged from a refrigerator. (Gorg Huff, "Other People's Money,"
Grantville Gazette,
Vol. 3). If the up-timers can duplicate the ribbon machines of our time line, then they can mass-produce light bulb shells.

In a fluorescent tube, the glass enclosure confines the mercury vapor. Electricity causes the latter to emit ultraviolet light, and this in turn stimulates a phosphor coating on the glass to absorb the light energy and re-radiate it as visible light.

Down-time glassblowers can certainly duplicate the tube itself, and mercury was available in 1632. The issues are how to inject the mercury safely, and how to obtain and apply the phosphor. I don't consider fluorescent lamps to be a practical development target for the USE, at least in the short-term.

A logical extension of the normal architectural use of the window is the greenhouse, which has glass walls and ceiling. Greenhouses would allow the USE to grow plants that can only thrive under tropical conditions, or to obtain additional crops of plants that die back or become dormant in the northern European winter. Soon after the Ring of Fire, "medicinal and ornamental plants were [being] grown in the glass-roofed conservatory" of Grantville's hospital (Ewing, "An Invisible War,"
Grantville Gazette,
Vol 2). If USE explorers venture into Latin America, they can bring back seeds of the
Hevea brasiliensis
rubber tree for greenhouse cultivation, and ultimate transplantation to a tropical country friendly to USE.

The concept of the greenhouse is not entirely foreign to seventeenth-century Europeans. De Serre protected individual plants by covering them with glass "bells" in 1600. There are also reports that orangeries with glass windows were established in Pisa (1591) and Leiden (1600) (Muijzenberg, 45). The greenhouse is quite practical if we can produce the necessary plate glass; "seconds" from the window glass factories would be probably be good enough.

Glass can be used in the windows of military vehicles and structures, but then we need to worry about the effect of enemy fire. A relatively low-tech way of reinforcing the glass is to use wire glass, which is sheet glass buttressed with a wire netting. Wire glass is made by lowering a wire mesh into a stream of molten glass. (Or by laying down a ribbon of glass, then the wire mesh, then another ribbon, and finally rolling them together.) Wire glass won't keep out a cannonball, but it will give some protection against, say, flying debris.

We should also be able to learn how to make tempered glass. The glass is heated to a high temperature and then cooled rapidly. The process increases the strength of the glass several fold, and also alters how it breaks; it powders, rather than forming dangerous shards. The duplication of tempered glass is a matter of determining, whether by library research or experiment, the necessary parameters, such as tempering temperature and cooling rate.

Both auto windshield "safety glass" and "bulletproof" glass are actually laminates of glass and plastic, and therefore must await the creation of a plastics industry.

One of the largest twentieth-century markets for glass is in the manufacture of fiberglass. Coarse glass fibers were made and used in pre-Roman times, but merely for decoration of tableware. In 1870, John Player developed a process for mass producing a glass wool, useable as insulation. A fire-retardant cloth, with interwoven silk and glass fibers, was announced by Herman Hammesfahr in 1880.

Grantville's
Encyclopedia Britannica
briefly describes a method of making fiberglass in which the liquid glass enters a spinning, perforated cup, the fibers are extruded through the holes, and blasts of air fragment the fibers. Another approach, set forth in the
World Book Encyclopedia
, is to melt glass marbles in a furnace with a perforated bottom, and collect the threads onto a spinning drum. The tension created by the pulling drum helps draw out fine glass fibers.

The USE should be able make simple glass wools and cloths, but fiberglass composites, such as those used in the hull of the speedboat
Outlaw
, require a mature plastics industry.

There are some military uses of mirrors which were not well established in 1632, but which could now be exploited by the USE. These include the following:

Periscopes 

The trench periscope, used extensively in World War I, was invented by the Polish astronomer Johannes Hevelius (1611-1687) in 1637. The first naval use of the periscope was in the American Civil War, where one was improvised by Chief Engineer Thomas Doughty of the Union ironclad
USS Osage
during the Red River campaign of April 1864. (A periscope would have come in handy during the
Monitor
-
Merrimac
engagement, as Captain Worden of the
Monitor
was blinded when a shell struck near the viewing slit of the pilot house.)