How to produce Clear Float Glass?

Clear float glass is made through the float process, which was invented by Sir Alastair Pilkington in the 1950s. It's how most flat glass (like windows, mirrors, and architectural glass) is made today. Here's the basic idea:

1. Prepare Raw Materials

The main ingredients are:

Silica sand (SiO₂) — the primary ingredient

Soda ash (Na₂CO₃) — lowers the melting point

Limestone (CaCO₃) — stabilizes the glass

Dolomite (MgCO₃·CaCO₃) — improves durability

Alumina (Al₂O₃) — enhances chemical resistance

Small amounts of other additives (to control properties)

These materials are carefully measured, mixed, and called a batch.

2. Melting

The batch is heated in a furnace at about 1500°C (2730°F) until it melts into a homogeneous, molten glass.

This stage must be super precise to avoid defects.

3. Float Bath (Tin Bath)

Here’s the magic:

The molten glass is poured onto a bath of molten tin.

Glass floats on tin because tin is denser, and gravity + surface tension spread the glass into a perfectly flat layer.

The thickness of the glass can be controlled by adjusting the speed at which the glass ribbon is drawn off.

4. Annealing

The still-hot, but solidifying, glass enters an annealing lehr (a long oven):

It is slowly cooled down in a controlled way.

This relieves internal stresses that would otherwise cause the glass to crack.

5. Cutting and Inspection

Finally:

The glass ribbon is cut into sheets of desired size.

Sheets are inspected for optical clarity, flatness, bubbles, or inclusions.

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