Glass and Windows

When I look to flesh out my worlds, to give them texture, I often turn to the materials of their making.  What do my people eat or drink?  What do they wear?  How do they construct their homes?  This leads me to dwell on their essential materials and where they came from, who first worked it out.  It's like the old idea of imagining the first person to see an egg come out of a hen's ass and say, "I want to eat that."  Many of the tools and materials humanity has used to build its world seem obvious.  I'm certain that stone, wood, and clay took little imagination to find their essential applications (though much artistry and brain power have been used to fine tune their uses).  One of those building-block materials that is a little harder to explain is glass.
    The basic foundation material for the creation of glass is silica (commonly found in quartz).  However, pure quartz takes some serious heat to make this change (over 1200degC), so we need a few additives to make it work.  Early recipes used quartz sand mixed with soda ash.  Impurities in the sand of certain regions  might give the glass a characteristic color, like the German waldglas, which has a green tint.  Eventually, recipes were also specifically developed to create various colors for decorative purposes (stained glass windows, mosaics, cameo glass, etc).  Lime, magnesium oxide, and aluminum oxide are common additives used to increase durability. 
    Like many great discoveries, glass is thought to have been stumbled upon as a byproduct, a beautiful accident.  Its origins may be as deep as 3500BCE in Syria, Mesopotamia, or Egypt.  At that time they were simply making beads or small decorative items.  Development may have occurred independently in other parts of the globe, but it seems to be found in all major population centers well before the Medieval period (which is what I generally care about, in terms of writing).  Around 1500BCE hollow containers started to be made by covering a sand core with molten glass.  Glass-blowing was discovered in the 1st Century BCE along the Syro-Judean coast.  Because of this, glass became less expensive than pottery for small containers and proliferated throughout the Roman Empire, though its making was a closely guarded secret. 
    Development of glass manufacturing in Europe came in fits and starts.  After the Roman Empire fell to bits, glass production decreased significantly until it was revived through Italian trade with Byzantium.  In Northern Europe, ca 1000CE, the widely available potash (do you remember this from a previous post?) came to replace the soda ash used in the South, significantly decreasing materials cost for production.  Around this same time, new methods were developed in Germany for producing sheets of glass from blown cylinders of glass (still relatively small panes).  The glass was thick and wavy, so while it would admit light, it was hard/impossible to see through clearly.  Windows constructed of this material remained primarily within religious buildings in Europe throughout the Middle Ages.  It took until the late 17th Century, around the time the Brits added lead oxide to the mix, for glass to become a common sight in windows of the common people of Europe.
    Local specialties arose throughout Europe, spawning some of the brands famous still on the market today.  Bohemian Crystal (rock crystal) production began in the mid 13th Century, with its intricately etched tableware (and later chandeliers and such).  The luxuriously colored Murano Glass was first produced in that Italian town in the late 13th Century (after the glassmakers were forced to leave Venice to protect it from fire).  In the 15th Century, a Murano glassmaker discovered how to make clear flat glass, making Murano the first glass mirror manufacturers in Europe at that time (though the technology quickly spread).  I'm sure there are other manufacturers of note, but this ain't no commercial. 
    Ah, what a thoroughly useful night of research.  It seems I'll keep shutters on my windows in general, but a lord may get some of those thick bottle-glass looking ones like those I loved in Prague Castle's majestic Vladislav Hall (thanks again Mr. Sula for the lovely book).  I can start putting my booze back in glass bottles (though earthenware jugs can be nice and characterful, especially for moonshine).  Glasses are a possibility for drinking out of, though I may stick with tin, pewter, or even horn for most regular folks.  As we discussed before, spectacles are generally off the list unless they're for priests.  Oh and remember people, if you want to manufacture glass, sand doesn't only come from the sea shore.  Take a wander sometime through Berlin's Grunewald for some nice sandy beaches (well sand and nudists around the Teufelsee). I hope you enjoyed this brief survey of the history of glass and that it made you think, just a little.

*as a side (er, end) note, much "stained glass" you see in churches is not colored glass, but clear glass which has been painted


good history - http://www.glasslinks.com/newsinfo/histppg.htm
muddle of history - http://en.wikipedia.org/wiki/History_of_glass
technical materials - http://en.wikipedia.org/wiki/Glass
general history - http://www.historyofglass.com/glass-invention/first-glass/
general history with techniques - http://timeline.cmog.org/
Murano - http://www.glassofvenice.com/murano_glass_history.php
for descriptions and diagrams of technique - http://mikegigi.com/tubeshet.htm
Bohemian Glass - http://mybohemia.com/glass_history.htm