How are Glass Bottles Made?

Blog post image, how bottles are made

Have you ever wondered how glass bottles are made?  Why the shape is designed for each type of use?  Why the color is selected? 
In the next few Blog posts, I will explore these topics.
If you missed one, Visit my website at BronwenHeilman.com/blog

In this first part, We will dive into: How Glass Bottles are Made

Glass (soft glass) is made out of 3 ingredients:
Silica Sand (45%)
Soda Ash (15%)
Limestone (10%)
Crushed Recycled glass (30%) (cullet)
Adding the recycled glass reduces the amount of energy needed to melt the batch of chemicals in the large melting crucible.  Think of a kind of flux.  Flux added to a solder joint helps keep the metals clean, and helps melt the solder quicker.
Note:  The amount of recycled glass is increasing, which also continues to save the amount of energy to melt the batch of glass.

Silica Sand is the “glassy” part of any glass
Soda Ash helps melt the Silica Sand 
Limestone makes the finished glass more rugged or less brittle.
Recycled glass.. crushed glass (or cullet) is gathered from our recycled bins, so keep washing out your bottles, and recycling them.

This mixture of ingredients melts together at about 2800 deg. F.  (A very slow process of mixing the ingredients while heating, then letting this molten glass sit for a long bit to offer the bubbles trapped in the glass to rise to the top and pop.

Once the glass is in it’s molten stage, a bit of glass drips out of the bottom of the crucible.  A scissor type of machine cuts a piece of molten glass (glob) into a precise amount needed for the bottle it will be making.

The glob is mechanically placed into a mold and blown from the bottom, making the neck and top of the bottle.  (Including any threads).

While still very hot and soft, the bottle is flipped over, placed into another mold, and blown into from the top into the shape of the mold.  The mold is opened, the blown bottle is removed and placed on a conveyor belt heading into the annealing chamber.

Either before or after the annealing each bottle is thinly sprayed with a lubricant which decreases the coefficient of friction and thus reduces the scratching during packaging and filling.  This lubricant consists of a tin oxide and other lubricating waxes. 

Once annealed, the bottles are packaged up and sent to filling companies.

Why use Glass containers?

  1. Glass uses less energy to produce than producing the same item in metal or plastic.
  2. Glass can be recycled infinitely.
  3. It’s a WIN-WIN!
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