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Welding arc produces electromagnetic energy, mostly in the form of ultraviolet and infrared radiation, which causes burns, injuries, and even cancer. That’s why welders are supposed to wear their personal protective equipment when working to protect their skin and eyes from intense radiation. PPE includes glasses, goggles, helmets, face shields, welding jackets, and gloves.
Recommended Reading – Best Welding Helmet Under $100.
Welding Helmets and Lenses
Welding helmets are probably the most important protective devices for welding. Not only do they protect your face from heat, sparks, and spatter, but they also have filter lenses that shield your eyes from damaging levels of light emitted by the arc.
A welding lens, an essential part of your helmet, is either a piece of glass or a filter, that reduces the amount of radiation that gets into your eyes. How much radiation a lens blocks depends on its shade. The shade number indicates the amount of light that passes through the lens and, thus, tells you the level of protection a particular lens offers. In a nutshell, the higher the lens shade number, the darker it is and the less light it allows to pass through.
What Do the Shade Numbers Mean
The shade number stated is based on the DIN rating, which is the standard way of telling how much light is being blocked by the glass. So a shade #10 lens is in effect a DIN 10 lens.
The shade number tells you how much light the lens or filter blocks. For example, a shade 3 lens blocks about 86% of the light, which means only around 14% of the light gets through. That’s still bright enough for you to see the work field. A shade 4 lens allows about 5% of the light. That’s a lot darker than the previous shade, but it still allows you to see your work. That’s why most auto-darkening lenses start around shade 3 or 4 — to allow welders to see the area before the arc activates the darkening of the filter to shade 9. At shade 9, only 0.037% of the light gets through. By the time you get to shade 13, only 0.00072% of the light gets through (1).
Lens Shade for Welding
Although lens shades can range from 0-14, welding lenses have shades that range from 4-14. Any shade below 4 is too light to protect your eyes. Shade 13 is considered the darkest, but is actually just the typically used darkest shade. In some cases, a shade 14 lens is needed for the job. How dark the lens is depends on what type of welding you’re doing.
The intensity of the light emitted by the welding arc or flame depends on amperage needed, and amperage is dependent on the thickness of your electrode. Basically, the thicker the electrode, the more electric current is needed. For instance, if you’re doing shielded metal arc welding (SMAW), you may be using rods that are anywhere below 3/32-inch thick to more than 1/4-inch thick. If you’re using an electrode that’s under 3/32”, which needs a current below 60 amps, then the OSHA minimum protective shade number is 7. However, OSHA’s minimum shade requirements are insufficient for many welders. A welder may use a shade 9 in the situation above. OSHA’s minimum shade requirement for arc welding using rods from 5/32” to 1/4″ thick, which use 160-250 amps, is a shade 10 lens. But the American Welding Society recommends a shade 12 lens for such purpose.
For most types of arc welding, you’ll need lens shades that vary from #9 to #14, depending on how intense the emitted light is. Again, the more current needed, the more light is generated. So, while you may need a lens shade #10 for arc welding at 60 amps, you will need a shade 12 when welding at 200 amps.
On the other hand, gas welding requires #4-#8 lenses, depending on the plate thickness.
Lens Shade and UV Protection
Welding arcs generally emit radiation whose wavelengths span from 200 nanometers to 1,400 nanometers. This wavelength range includes ultraviolet radiation (UV-A, UV-B, and UV-C), visible light, and infrared radiation.
Now, a common misconception is that the shade alone blocks UV rays. However, the shade number doesn’t indicate how much UV light is filtered. The danger of this is that the darker lenses dilate the pupils of your eye more. If a dark lens has no UV filter, it will allow more ultraviolet radiation to get through to cause significant damage to the sensitive structures in your eyes. Most people and even some professional welders don’t know this, perhaps because all quality welding lenses in the United States come with UV filters. A UV-coated lens or filter should block 100% of incoming ultraviolet radiation. Thus, it’s important that you buy only good welding lenses.
Welding is a hazardous hobby or job that requires you to wear protective equipment, which includes a helmet. The helmet should be equipped with a lens of the right shade. Welding lens shades vary from 4 to 13, sometimes even 14. The higher the shade number, the darker the lens. The darker the lens, the more light it blocks. Choosing the right lens shade allows you to do your work without hurting your eyes.