Natural glass by God, gem by man


Glass, man’s contribution to God’s natural gems and geological creations, has been of interest to myself since I was about 10.

When the neighbors and I would play good and bad guys I preferred to carry a bag of costume jewelry and loose pieces of necklaces as my treasure. I was usually an explorer or mountain man.

Since that time, knowledge of glass making and the end products of the industry have been off and on a part of my life.

In the 1960s the interest was bottles. Our son, Bob, and I dug, traded, picked up and acquired over 10,000 different specimens. Although most have now gone by the wayside, a few unusual and rare pieces of glass bottles now remain.

Designer glass. I recently visited Hartville Restaurant and admired the hundreds of Fenton glass articles. The excellent display of color and detail renewed a bit of the interest.

The various colors, combination of colors and expertise required is the substance of wonder and mystery to any new or experienced person with glass culture interest. Many secret formulas and methods were employed to create most of the unusual glass colors and hues.

Secrecy. Behind closed doors, late night experiments and seemingly supernatural procedures cause envy and competitors’ attempts to duplicate the look.

Essentially all glass is crystal clear and merely colored via chemistry. Lead or lime glass are most often used for pressed or blown glass items. Lead glass is heavy and the ingredients are quality silica sand, potash and lead oxides. Lime glass is the same silica sand, soda ash and lime.

Lead glass is soft enough to cut and reveals a bright, prismatic surface, and this is cut after the object has become cold. Lime glass cools more easily than lead glass and requires work to be finished on its surface without waiting too long. The surface dulls when contacting cast iron molds; however, brightness can be restored upon warming it over a flame.

Lime glass is most often used by container manufacturers. The cost is about a third of lead glass.

Obtaining color. Colors can be obtained by adding impurities, such as iron oxide, which creates greens of all hues and a bluish green, such is found in old fruit jars.

Manganese added to a batch of greenish molten glass causes it to become colorless. Over time this manganese creates a purple when exposed to strong sunlight for a length of time. Violet or purple hues can also be obtained by nickel.

Copper creates a blue color but not the deep blue that cobalt makes. Green is generated by iron or chromium ingredients, uranium or mixtures of iron and ceruim.

Iron manganese compounds create an amber coloration.

A quality that is interesting is that the glass articles containing manganese or uranium give off a florescence when exposed to a black light.

Milk glass. Opalescent or milk glass is caused by sodium aluminum fluoride, called cryolite, tin oxide or calcium phosphate. Several shades of white or opal occur. They can be cloudy or shining white.

Black glass can be created by a dark red, seen usually along the edges or around the bottom when held to a bright light. The same examination will reveal dark purple.

Ruby or pigeon red has gold whereas the off-red (yellowish in some instances) is made by copper or selenium. Ruby red (gold ingredients) is time consuming and, of course, more expensive. True ruby red is not found in pressed glass wares.

Everyone who admires glass objects naturally has their favorite colors or articles. When admiring quality glass wares, such as Fenton’s products, remember these objects of art and expertise are made via science not by novices. Colors may have been discovered by happenstance but the work is exacting.


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