Glass Types & Properties
Annealed, tempered, laminated, heat-strengthened, wired, and safety glazing - definitions, break patterns, and code requirements for the Red Seal Glazier exam.
- Define annealed glass and explain its manufacturing process
- Describe the tempering process and identify where tempered glass is required by code
- Explain the construction and purpose of laminated glass
- Distinguish between heat-strengthened and fully tempered glass
- Identify the three types of safety glazing and their applications
Leçon 1
Annealed & Float Glass
What Is Annealed Glass?
Annealed glass is the most basic form of flat glass used in construction. It is produced using the float glass process, where molten glass is floated on a bed of molten tin to create a perfectly flat, uniform sheet. After forming, the glass is slowly cooled in a controlled process called annealing - this gradual cooling relieves internal stresses, making the glass easier to cut and fabricate.
The annealing process is critical because it determines the glass's workability. Glass that is not properly annealed retains internal stress and is prone to cracking during cutting or drilling. On the Red Seal exam, remember that annealed glass is float glass that has been slowly cooled to relieve stress.
Annealed Glass
Cooling: Slow, controlled
Internal stress: Minimal
Can be cut: Yes
Break pattern: Large sharp shards
Tempered Glass
Cooling: Rapid (quenched)
Internal stress: High compression
Can be cut: No
Break pattern: Small fragments
Properties of Annealed Glass
Annealed glass has several important characteristics:
- Clarity - excellent optical quality with minimal distortion
- Workability - can be cut, drilled, edged, and polished after manufacturing
- Uniform thickness - the float process produces glass in standard thicknesses from 2mm to 25mm
- Brittleness - breaks into large, dangerous shards when fractured
The primary limitation of annealed glass is its break pattern. When it fails, it produces large, jagged pieces that pose serious laceration hazards. This is why building codes restrict the use of annealed glass in hazardous locations such as doors, shower enclosures, and low-height glazing.
Annealed glass is float glass that has been slowly cooled to relieve internal stress. It can be cut and fabricated but breaks into large dangerous shards, which is why codes require safety glazing in hazardous locations.