Module 7 of 10 240m 240 min 9 exam Qs 9 exam questions covered
Mirrors, Spandrel & Fire-Rated Glass
Mirror silvering, black edge prevention, spandrel glass, fire-rated assemblies, delamination, and glass thickness selection.
- Explain mirror construction and black edge prevention
- Describe spandrel glass applications and opacifier requirements
- Identify fire-rated glazing types and their rating periods
- Explain glass delamination causes and prevention
- Apply wind load tables for residential glass thickness selection
Lesson 1
Mirrors & Silvering
Mirror Construction
A mirror consists of a glass substrate with a reflective coating applied to the back surface:
- Glass - clear float glass substrate (typically 3mm-6mm)
- Silver layer - thin reflective coating deposited on the back
- Copper layer - protective barrier over the silver
- Paint backing - seals and protects the metallic layers
Black Edge (Edge Corrosion)
Black edge occurs when moisture penetrates the mirror edge and corrodes the silver layer. Prevention requires: sealed edges (edge sealant or tape), proper ventilation behind the mirror, and keeping mirrors away from moisture sources. Never install mirrors directly on wet or damp surfaces.
Mirror Installation
- Mount with mirror mastic (compatible with silver backing) or mechanical clips
- Never use acidic sealants - they attack the silver coating
- Provide ventilation space behind the mirror (1/4 inch minimum)
- Use only mirror-safe adhesives approved by the manufacturer
- Ensure the wall surface is flat and dry
1/4 in
Minimum Ventilation Space Behind Mirror
Mirror Mastic
Primary Adhesive for Mirrors
Key Takeaway
Mirrors have silver and copper layers protected by paint backing. Black edge is caused by moisture corroding the silver layer - prevent with sealed edges and ventilation. Use only mirror-safe mastic and never acidic sealants.