Welding glasses work by filtering out harmful light and radiation produced during welding, protecting the welder's eyes from damage. The key component is a special filter lens.
The Filter Lens Explained
The filter lens is the heart of welding glasses and helmets. It's designed to:
- Block Intense Visible Light: Welding produces extremely bright light that can overwhelm and damage the retina. The lens significantly reduces the amount of visible light that reaches the eye, allowing the welder to see the weld pool and surrounding area without being blinded.
- Absorb Ultraviolet (UV) Radiation: UV radiation is invisible but highly energetic and can cause burns to the cornea (photokeratitis, also known as "welder's flash" or "arc eye") and long-term damage like cataracts. The filter lens absorbs almost all UV radiation.
- Absorb Infrared (IR) Radiation: IR radiation is also invisible and produces heat. Excessive exposure can lead to cataracts and retinal damage. The filter lens blocks much of the IR radiation.
Types of Filter Lenses
Welding lenses come in different "shades," which indicate the level of darkness and protection they provide. Higher shade numbers offer more protection.
- Fixed Shade Lenses: These are traditional lenses with a single, pre-determined shade number. They are typically made of tinted glass or plastic.
- Auto-Darkening Lenses (ADL): These lenses use electronic sensors to detect the arc's light. When an arc is struck, the lens automatically darkens within milliseconds to a pre-set shade. Once the arc is extinguished, the lens returns to a lighter state. This allows welders to see clearly before and after welding without having to lift their helmet. ADL lenses often allow welders to adjust the shade, sensitivity (how easily it darkens), and delay (how quickly it returns to the light state).
Lens Shade Numbers
The appropriate shade number depends on the welding process and the current (amperage) being used. The American Welding Society (AWS) provides guidelines. Here's a simplified example:
| Welding Process | Amperage Range | Recommended Shade |
|---|---|---|
| Shielded Metal Arc Welding (SMAW) | < 80 | 3-4 |
| Shielded Metal Arc Welding (SMAW) | 80-175 | 5 |
| Gas Metal Arc Welding (GMAW) | < 80 | 3-4 |
| Gas Metal Arc Welding (GMAW) | 80-175 | 5 |
| Gas Tungsten Arc Welding (GTAW) | < 80 | 5 |
| Gas Tungsten Arc Welding (GTAW) | 80-175 | 5-6 |
Important Note: These are just examples, always refer to the AWS guidelines or the manufacturer's recommendations for the specific welding process and equipment being used. Using an insufficient shade can cause serious eye damage.
Construction
Welding glasses and helmets typically consist of:
- A Frame/Helmet Shell: Provides physical protection against sparks, spatter, and debris.
- The Filter Lens: The core component for optical protection.
- Cover Lenses (Optional but Recommended): Clear plastic lenses placed on the front and back of the filter lens to protect it from scratches and spatter, extending its lifespan.
In summary, welding glasses and helmets employ a filter lens that selectively blocks harmful light and radiation, enabling welders to safely view the welding process and avoid potentially severe eye injuries. Different welding processes and amperage settings require different lens shades to offer adequate protection.
