Fulgurites

Examples of fulgurites or petrified lightning

The WebEcoist has a nice article on fulgurites which are a type of natural glass formed when lightning strikes silica-rich soil. From the article…

The word fulgurite is derived from “fulgur”, which means “thunderbolt” in Latin. That’s just part of the story, though, as the real action begins once the bolt hits the ground. The average lightning bolt packs up to a gigajoule of energy – enough to power an all-electric home for about a week, or around 300 kilowatt-hours. When a strike enters the ground it makes its presence known by vaporizing soil & sand along a downward, branching path that may be up to 20 feet long. Temperatures of up to 50,000 degrees blast sand (silicon dioxide) into a hollow tube lined with what is essentially glass: a fulgurite.

photo

Advertisements

November 4, 2009 at 4:26 pm Leave a comment

Glass Blowing

Glass blowing is a form of art which has existed for many centuries. Before the 1900s glass blowing was more of a practical glassware production technique rather than a dedicated art form. There weren’t any technological alternatives to making glassware other than hand blowing. In fact, many of the early chemists were proficient glass blowers because they hand to make their own custom glass to carry out their chemistry experiments. During the later part of the industrial revolution manufactures began to automate the production of glass products. It was at this point in history that glass blowing really emerged as an art form. However, interest waned in the new art form beginning in the early 1930s. It wasn’t until the 1960s, when glass blowing enjoyed a tremendous revival.

Today there are many artisans creating quality blown glass works of art in many different forms. Pieces range from glass vases and faucets to more decorative works of art. A great example of decorative art work is Dale Chihuly’s Fiori di Como. Fiori di Como is a very large series of flowers that hangs from the ceiling of the Bellagio Hotel and Casino in Las Vegas, Nevada. Fortunately, you don’t have to commission an artist to create blown glass artwork to be able to enjoy the beauty of hand blown glass in your home. Companies like Blenko Glass Company produce early collections of beautiful vases, decanters, bowls, bookends, pitchers, candle holders, and ornaments. You can also purchase tumblers and carafes as well. Most of these pieces of art can be procured for less than $200.

July 27, 2009 at 3:43 pm Leave a comment

How Flat Glass Is Made

We have a rough idea of the ingredients that make up glass, but how do these powders turn into large sheets of glass? The answer is a long production line known as a float glass process.

The raw materials are mixed together in a batch blending process. Then they are fed into a very large furnace. These furnaces are 140 feet long and 30 feet wide. In the furnace, the ingredients are heated to about 2700° F at which point they form into molten glass. The glass melt is then moved into a delivery channel where it is brought to a uniform 2200° F. The melt passes through a control gate and then is poured onto a shallow pool of liquid tin. This part of the process is the really cool part.

The glass melt floats on the pool of tin. This creates very smooth and uniform glass and is a huge improvement over past glass manufacturing techniques. Tin is really an optimum choice as the liquid for the flotation pool. Tin is relatively dense which insures that the glass melt will float on the surface of molten tin rather than sink. Glass and tin are immiscible. This means they will not mix together.

A byproduct of tin, tin dioxide, will adhere to the glass which is problematic. If tin is in the presence of a source of oxygen, air for instance, tin dioxide readily forms. Glass manufacturers keep oxygen away from the tin by using a pressurized mixture of nitrogen and hydrogen gas.

As the layer of glass floats across the surface of the pool, it begins to cool and solidify. Once the glass becomes solid, it is lifted off the bath and onto rollers at 1100° F. The rollers mark the beginning of a 350 foot long annealing chamber, a lehr kiln, that allows the glass to slowly enough to avoid cracking or otherwise damaging the glass. After the glass leaves the lehr kiln section of the manufacturing process it is ready to be cut into smaller panes.

March 19, 2009 at 4:22 pm Leave a comment

Antimony Trioxide

By adding sodium bicarbonate, calcium oxide, magnesium oxide, and aluminum oxide to silica, you can make very chemically durable glass. However the glass isn’t perfect yet. Tiny pockets of air tend to get caught in the melt while it’s being mixed and poured. The resulting bubbles can cause performance and aesthetic issues in the final product.

You need to add a fining agent to the mixture to get rid of the bubbles. An example of a common fining agent is antimony trioxide. The antimony oxide causes smaller bubbles to come together and form larger bubbles. The smaller bubbles raise to the surface of the melt very slowly while larger bubbles travel relatively quick. With the addition of a fining agent and a bit of patience, glass will be bubble free. Photo: wiccked

March 4, 2009 at 2:19 pm Leave a comment

Calcium Oxide

So sodium bicarbonate is useful in that it significantly lowers the glass melting point of silica. However, adding sodium bicarbonate also presents a serious side effect in that the resulting glass is water soluble. This means that if you tried to put something as simple as water in a drinking glass the water would start to dissolve the glass. Researchers discovered that one of the more popular uses for glass was to hold stuff, namely wet stuff. Something had to be done to fix this problem. Turns out including another ingredient does the trick

Adding about 5 percent calcium oxide to your silica and sodium carbonate mixture is very effect at improving the durability of glass. A major source of calcium oxide is limestone and hence, the “lime” portion of soda-lime glass comes into the picture. You can further improve the chemical durability of glass by a few percent or less of magnesium oxide and aluminum oxide.

March 4, 2009 at 3:09 am Leave a comment

Sodium Bicarbonate

Ninety percent of man-made glass is a type of glass known as soda-lime glass.  The soda-lime designation comes from some of the ingredients in the glass.  Although it is possible to produce and there are special applications for glass made from pure silicon dioxide or silica, it is a fairly complex and expensive process.  The inclusion of a few additives makes producing glass less expensive and simpler.

A primary additive is sodium bicarbonate.  Sodium bicarbonate is the soda in soda-lime glass.  Sodium bicarbonate is a very common chemical.  So common in fact, that you probably have some in your kitchen in a box labelled baking soda.  It is also known as soda ash.  The glass melting point of pure silica is 4300 °F.  If you add 15 – 20% soda ash to the glass mixture, you can lower the melting point to around 2700 °F. This is a significant reduction which results in energy savings and less expensive handling equipment.

March 2, 2009 at 12:10 am Leave a comment

Tektites

Another of nature’s natural glass production mechanisms is when large meteorites strike the Earthy’s surface.  the intense temperature and pressure that result from a meteor impact cause little pieces of rock to melt almost instanteously.  The molten rock is squeezed out of the forming crater and then cools as it travels, sometimes for hundreds miles, through the air into small pieces of glass known as tektites.  Tektites are usually black or dark green in color and rounded or irregularly shaped.  Even though a meteorite impact produces the tektites, it is generally believed that tektites are made from the rocks and soil that were in place before the strike.

February 24, 2009 at 6:08 pm Leave a comment

Older Posts