Defect of the Month

July, 2019
Toxic Swirl
This iron stone has reacted with the surrounding glass, creating a telltale greenish-brown swirl. Bottle caps and lids are a possible source of iron contamination in recycled cullet, but the use of magnetic separation usually prevents widespread problems from occurring. The internal cullet supply can be more vulnerable, however, and nuts, bolts, wire, or even mold parts have been known to find their way into the furnace.
February, 2019
Atmospheric Weathering
This piece of weathered glass was viewed in our Scanning Electron Microscope (SEM), magnified 800X and shows the crystalline structures on the inside surface of a glass container. By colorizing the elements we were able to differentiate between the Calcium and Sodium Carbonates. In this view the calcium carbonate (blue) is along the edge of the sodium crystals (purple). This atmospheric weathering is evidence of the reaction of the mobile ions of calcium and sodium in the glass with the atmosphere.
January, 2019
This “snowflake” is actually a crystalline inclusion embedded in solid glass as viewed through a microscope. When a silica rich area of the glass melt cools below the liquidus temperature, crystals of tridymite (SiO2) such as those shown here can form. Tridymite crystals can also form in the vicinity of a silica batch stone.
December, 2018
This crystal formation of atmospheric weathering is composed of calcium and sodium carbonates on the inside surface of a glass container. This unusual weathering formation has the appearance, when colorized on our scanning electron microscope, of a holiday wreath.
November, 2018
Diatomaceous earth
Diatomaceous earth–is a naturally occurring, soft, siliceous sedimentary rock that consists of fossilized remains of diatoms. Diatomaceous earth is a thermal insulator and primarily composed of silica and is sometimes used as a refractory packing material in the glass industry. This is an unused sample that was analyzed to compare physical and compositional properties to a stone analysis.