How glass bottles are made
Every bottle starts as a glowing glass sausage sheared off a falling stream, then gets blown twice.
- stations
- 8
- things upstream
- 21
- raw sources
- 11
- steps from the ground
- 5
The short version
A glass bottle begins as a measured blob of molten glass, called a gob, sheared from a stream at about 1,050 to 1,200 °C. Compressed air blows the gob into a small rough shape, then into the full bottle in a second mold. An annealing oven relieves stress, and a coating protects the surface.
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Weigh the batch
A batch house measures sand, soda ash and limestone, mixes them with crushed scrap glass and feeds the blend into the furnace. The recipe changes with the color and purity the bottle needs.
Goes in -
Melt it in the furnace
Furnaces for container glass are fired by natural gas or fuel oil and can reach 1,575 °C. They are rated by how many metric tons of glass they deliver per day.
up to 1,575 °C
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Shear off a gob
A blade cuts the stream at its plastic temperature into a cylinder of glass of exactly the weight one bottle needs. The gob falls by gravity through troughs and chutes into the first mold.
1,050–1,200 °C
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Blow the rough shape
In the blank mold, compressed air or a metal plunger forms the opening of the bottle, called the finish, and a small hollow body called the parison. The "blow and blow" method is used for narrow necks, and "press and blow" is used for jars.
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Flip and blow to size
An arm swings the parison upside down into the final mold. A last blast of air blows the glass out against the mold walls. One machine has 5–20 identical sections, and each section can make one, two, three or four bottles at once.
5–20 sections per machine
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Treat the inside
Bottles for spirits often get a puff of sulfur- or fluorine-bearing gas while hot. It makes the inner surface more resistant to alkali leaching, which can raise the pH of what is in the bottle.
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Anneal in the lehr
An annealing oven heats the bottles to about 580 °C and then cools them slowly, so uneven shrinking does not leave them brittle.
20–60 minutes
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Spray, inspect and pack
A polyethylene coating goes on after annealing for scratch resistance and slipperiness. Machines then check each bottle for defects before it is packed.
Goes in
Worth repeating
- The first glass bottles were made in Mesopotamia around 1500 B.C.
- Michael Owens built the first automatic bottle machine in 1904 after working on lightbulb production for Edison.
- In the Nordic countries, bottle return rates of 95% are not uncommon.
Back to the ground
Follow every input upstream and glass bottle starts as these 11 raw sources.
Everything it is made of See it on the map
Open the whole family tree
Where it goes next
Glass bottle feeds 31 lines directly and reaches 37 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How glass bottles are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/glass-bottle