How are Sunglasses Tinted?

Sunglasses are tinted primarily through two methods: heat-treated dye absorption and a constant density process.

Heat-Treated Dye Absorption

This is the most common method, especially for plastic lenses. The process involves immersing the lenses in a specially formulated chemical dye bath. The bath is then heated, causing the lens material to expand slightly. This expansion allows the dye molecules to be absorbed into the lens. The longer the lens remains in the dye bath, the darker the tint becomes.

• Suitable Materials: Most plastic lens materials are compatible with this process.
• Process:
  1. Lenses are cleaned and prepared.
  2. Lenses are immersed in a heated dye bath.
  3. Tint density is monitored carefully.
  4. Lenses are removed, rinsed, and cooled.

Constant Density Tinting

This method is frequently used for glass lenses, especially non-prescription (Plano) lenses. Unlike the heat-treated method, the tint is incorporated into the lens material during the manufacturing process. This results in a consistent tint density throughout the lens.

• Suitable Materials: Primarily used for glass lenses.
• Process: Dyes are added to the molten glass during manufacturing ensuring that color is embedded within the lens itself, creating a uniform tint.

In summary, sunglasses achieve their tint primarily through heat-treated dye absorption (common for plastic lenses) or constant density tinting (common for glass lenses), each offering specific advantages depending on the lens material and desired outcome.