Modern mirrors, commonly found in homes and vehicles, are primarily manufactured using a process called wet deposition, typically involving silver or aluminium. This method allows for a thin, reflective metallic coating to be applied uniformly onto a glass surface.
The Wet Deposition Process
The manufacturing process begins with the glass substrate itself, which is the foundation of the mirror. This glass needs meticulous preparation before the reflective layer can be applied.
Step 1: Glass Preparation
The initial and crucial step is the thorough cleaning and polishing of the glass surface. This stage is vital to ensure the removal of impurities and contaminants that could interfere with the bonding of the reflective coating or lead to imperfections in the final mirror.
- Cleaning agents are used to wash away dirt and residues.
- Polishing might be employed to create a smooth, uniform surface.
Step 2: Applying the Base Layer (for Silver)
According to the manufacturing reference, if silver is used as the reflective material, a series of coatings is required. The process specifically begins with the application of tin chloride. This is necessary because silver will not bond directly with glass. The tin chloride acts as an intermediary layer, creating a surface that the silver can adhere to effectively.
- A thin solution of tin chloride is applied to the prepared glass.
- This creates a reactive surface for the subsequent silver layer.
Step 3: Depositing the Reflective Layer
This is the core of the wet deposition process. A chemical solution containing the chosen metal – either silver or aluminium – is applied to the glass surface. Through a chemical reaction, the metal ions in the solution are reduced and deposited as a thin, uniform metallic film onto the prepared glass.
- For silver mirrors: A silver nitrate solution and a reducing agent are applied, causing silver to precipitate onto the glass.
- For aluminium mirrors: Often, a different technique like vacuum deposition is used for aluminium in higher-end mirrors, but wet deposition methods can also be adapted. The provided reference highlights wet deposition for both silver and aluminium in a general context for modern mirrors.
Step 4: Protection and Finishing
After the reflective metallic layer is applied, it is typically very thin and susceptible to damage from moisture and abrasion. Therefore, protective layers are added.
- A protective paint or coating is applied over the metal layer to seal it and protect it from the environment.
- This backing paint is often grey or green in common mirrors.
While the provided reference focuses on the critical steps of cleaning and the initial metallic deposition using wet methods, particularly highlighting the need for tin chloride before silver, the overall process ensures a durable and highly reflective surface essential for a functional mirror.
