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How Bottles Made
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How Glass Bottles are Made

 
HOW GLASS BOTTLES ARE MADE
THE ideal glass would be made of pure sand. But as pure sand cannot be melted, other elements must be added. Soda ash will melt the sand, but forms a silicate which is soluble in water. Hence, additional ingredients must be used. Limestone and feldspar give the needed resistance to weathering and the action of water. Cullet, or waste glass, is added both to regain the waste and to improve the working qualities of the mixture, while borax reduces the coefficient of expansion and makes the finished product better able to stand temperature changes. Barytes cleans the glass and gets rid of all gases, while various decolorizers are used to neutralize anything which might keep the glass from being clear and white.
The ingredients of glass vary with the color desired. All glass contains sand, soda ash, cullet, feldspar, borax and barytes. In addition to this, flint glass contains burnt dolomite lime, arsenic, and two decolorizers.

Whitall Tatum Company sand dredge

Sand is the principal ingredient in bottle manufacture. Many kinds of sand are used by different manufacturers because of necessity. But it is generally accepted that the very best deposit of bottle sand is only three miles from Millville, N.J., and is owned by the Whitall Tatum Company. Above you see part of the pit, the sand being dredged out by hydraulic machinery and pumped to the cleaning and storage sheds. Operators watch for prehistoric bones buried here. Also for "lightning canes" made by lightning striking the sand and fusing it into a crude glass.