Defect of the Month

November, 2019
“The possibility of successfully navigating an asteroid field is approximately 3,720 to 1!” This famous movie line captures the appearance of the microscope image shown here. In this case, the “asteroids” are actually clumps of unmelted silica (SiO2) grains in glass. Although the clumped nodules were unusual, the individual grains were typical of silica batch stones. Silica batch stones are caused by a number of batching or melting issues, including increased furnace pull, batch segregation, or insufficient melting temperatures.
October, 2019
Crizzled finishes contain numerous cracks that extend both radially and circumferentially around the top of the finish. In contrast, split finish defects consist of a single, radially oriented crack across the finish. A crizzled finish poses a risk for leakage, and is a critical defect if it allows leaking or spoilage of the product. As with many check-like defects, crizzle is caused primarily by molds that are too cold during container formation. This picture and description come from AGR’s “Color Atlas of Glass Container Defects”
September, 2019
Dot Code Collision
The origin of this breakage (above the arrow) is a percussion cone defect. This specific percussion cone was the result of the dot code of one bottle impacting the dot code of another bottle. In this bottle design the dot codes are incorrectly located in the normal bottle contact zone and not the recessed portion of the heel. In this instance improved handling would not be helpful to eliminate the breakage. Rather an improved design is needed.
August, 2019
Rusted Butterfly
During container manufacture, molten glass is blown out into molds using pressurized air. Contaminants in the air supply, such as the particle of rust shown here, can become embedded on the inside surface of the newly formed bottle. In this SEM micrograph, the bubbles and dissolved metal stretched into the surrounding glass suggests that the rust particle was deposited during blowing out of the parison (i.e. blank). The interesting pattern was created when embedded material was distorted by expansion in the blow mold.
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.