Glass, who invented glass?  Where did it come from?

Pontil on Glass being blown 

Well, it is believed that glass was invented around 3000 BC during the Bronze Age.  It is formed when certain rocks melt due to high temperatures and cools and then solidifies rapidly.  From the discovery of glass, I believe is the proper theory, many products have been produced; windows, glasses, bottles, mirrors, decanters, dishes, and jewelry.  Glass has been used as weapons and tools.  Glass has become an integral part of our daily needs.  We all have at least one mirror in our home, and personally I dare not leave the house without viewing my image.

There are 3 main steps to making glass.

1.  Sand (which apparently is the main ingredient 75%) and other raw material (sodium carbonate 10%, limestone 5%, and alumina 5%) are heated in a furnace to about 1500C.  When this melts it forms molten glass.

2.  The molten glass is transferred , molded or shaped and placed in a kiln.  You have the "blow blow" techniques.  (Of course I am describing today's methods) This technique uses compressed air to give bottles its form.  Then they use the "press blow" to give the bottle its final shape.  The glass is then reheated in a kiln to cool the glass evenly to give it a smooth finish and make it strong.

The original methods were, blown (freeblown or offhand blown), pattern molded or blown molded glass (molten glass blown into a mold) and blown three mold (the glass was blown into several molds and seamed together) and finally pressed glass (molten glass placed in a mold and pressed down with a weight) no blowing in this technique.

3.  The glass is inspected, packaged and shipped.

Many inventions and techniques have been created to create glass and shape a variety of glass.  It is overwhelming when you realize the importance of glass. 

Soooo, what makes glass objects a commodity, a collectible, an antique, precious and priceless?  Well glass is a challenge it has gone through changes and fads, and some are just difficult to identify and place a time to.  So here are some tidbits.  The most important tidbit to keep in mind is that in the past 50 or so years glass has been reproduced, and many from the original molds, and are difficult to identify and time.

For dating glass remember that colored glass became popular after the Civil War.  Yes colored glass was produced prior but the main focus at the time was transparent glass.

If your piece has blobs of glass added to it, it's more than likely a late 19th century piece.  Blobs are also known as threading, lily pad and prunts.

1894 - 1935, iridescent glass; Louis Comfort Tiffany, glass signed L.C.T. or Tiffany, or L.C. Tiffany or Favrile.  If mark missing can only be ID'd by an expert.

Quezal glass 1901 - 1920, all is supposed to be marked.

Durand glass 1897 - 1935, mark is "V" most not marked though

Aurene, 1904, marked "Steuben" or  "Carder"

Golden iridescent 1890 - 1924 by Union Glass Company, signed "Kew Blas"

Carnival Glass, 1900 - 1920, cheap pressed glass, (has been greatly reproduced).  Marks are "I" & "G" overlapping, , "N" or "N" in a circle.

Pressed Glass, late 1820's.  Pieces made prior to 1840's are in demand, (ribbed and heavy looped), 1860's flowers, 1870's clear and frosted more elaborate patterns such as daisies, grapes, and figures.

Cut Glass, 1715, 1760, 1771 -1830), What's the difference between cut and pressed glass?  Cut glass has sharp edges, and when tapped it rings with a clear tone, cut glass is heavy, sparkles and reflects light.  Pressed glass edges are rounded (from being in a mold) and dull to the touch, and when tapped the tone is dull and flat.

Depression Glass, late 1920 - 1940's.  This was glass produced during the Great Depression.  Manufactured by Federal Glass and Hocking glass companies Depression glass is a popular collectors item.   Colors include pink, green, cobalt blue, green, white, amber, iridescent and many more.  One way to recognize Depression glass is little bubbles in the glass; mold marks and imperfections...remember Depression glass is a cheaply made glass that was purchased in Five & Dime stores.

Vaseline Glass, 1870's greenish yellow, originals contain uranium.  Called Vaseline glass because it resembled the blue-yellow color of petroleum jelly.  Also called canary glass.

Milk Glass (Slag), 1870 - 1880's.  Called milk glass because it resembled milk.  Comes in various colors of blue, (light and dark) green, amethyst, and black...no chocolate milk for this glass.  Difficult to determine age and there is a lot of it out there.  Old ones can be identified by a "C" rough spot on the bottom, and old pieces have less blue in them, and the glass is heavier.  NOTE: some new pieces have been made from old molds.

So what the difference between milk glass and slag?  Slag has steaks running though it like marble, 1880 - 1900's   it was reproduced in the 1960's.  Think of fudge marble ice cream on a "slag" of cake.

Satin Glass, late 1880's, velvety finishes with white lining.

Well this concludes my tidbits on identifying and dating glass.  Hope it was helpful.

Susanna's Treasures