How is glass made?

How Glass is Made – Crafted from Earth's Dust

1. Gathering Earth's Bones
Sand, Ash, Stone: Workers dig up quartz sand (main ingredient), then mix it with soda ash (lowers melting point) and limestone (stabilizes). Scrap glass (“cullet”) is added to speed melting.
No Exact Recipe: Colors or properties change with additives — cobalt for blue, lead for crystal sparkle, boron for heat resistance.

2. Blast Furnace Alchemy
Meltdown: The mix is shoveled into a searing furnace (≈ ancient volcano). At white-hot temperatures, sand grains fuse into a thick, glowing syrup.
Molten Dance: For 24+ hours, bubbles rise and die in the lava-like pool. Workers skim off impurities like blacksmith purifying iron.

3. Shaping the Liquid Light
Ancient Breath (Hand-Blown): A craftsman dips a pipe into the furnace, gathers a gob of molten glass, then blows through the pipe—spinning, swinging—to create vases or bottles. Breath gives it shape.
Modern Machines (Pressed/Cast):
Bottles/Jars: Molten glass flows into molds, compressed by air like inflating a balloon inside a cage.
Window Panes: Liquid glass floats on a bed of molten tin—spreading into flawless flat sheets.

4. The Slow Art of Cooling
Annealing: Freshly shaped glass enters an oven called a "lehr". Temperature drops slowly over hours—sometimes days. Rushing this makes glass shatter like ice.
Why It Matters: Uneven cooling locks in invisible stresses. Annealing lets molecules relax, turning fragile form into enduring solid.

5. Finishing Touches
Grinding & Polishing: Rough edges are seared off with flames or sanded smooth. Decorative cuts are etched by hand or acid.
Tempering for Strength (Optional): For car windows or ovenware, glass is reheated then blasted with cold air. This skin-deep tension makes it fracture into safe crumbs, not daggers.