Is this an artist’s conception of the “Emerald City” from the Wizard of Oz? In actuality, this strange-looking defect was found at the fracture origin of a broken beer bottle. Analysis with a scanning electron microscope revealed that the “arches” are actually distorted bubbles inside the glass. Remnants of silicon detected around the fracture origin were telltale signs that a silicon ball inclusion had caused the breakage. The bubbles shown here were byproducts of the reaction between aluminum metal and the molten glass that produced the silicon ball. Even though the silicon ball itself was missing, enough evidence remained to determine the cause of failure.

In this microscopic view, the sealing surface on the top of the bottle finish shines blue from reflected light. The diagonal line going from upper left to lower right is a type of crack known as a “split finish.” This split finish was created during manufacturing when a piece of broken glass was pressed against the side of the threads. The rounded lip of the crack reveals that it was created when the glass was still very hot, allowing it to partially heal before the glass completely cooled.

Crystals of perfume compounds appear in rainbow colors to either side of a crack (dark line) in this polarized light microscope image. An extremely thin fracture running through a perfume sample vial allowed just enough space for product to seep through. Next, the alcohol-based solvent slowly evaporated, growing these crystals on the surface of the vial.

Corundum (α-alumina) crystals, viewed in a thin section under polarized light. When aluminosilicate minerals react with molten glass, several types of crystals can precipitate from the dissolving inclusion. Corundum, shown here, forms hexagonal plates near the center of the solution sac. Sources of aluminosilicate impurities include ceramic or pottery cullet contaminants as well as degrading aluminosilicate refractories in the furnace.