Answers to common questions about welding helmet filter lenses and cover lenses, from shade numbers to fit and fogging.
What do the shade numbers on a welding lens mean?
The shade number tells you how dark the filter is. The higher the number, the darker the lens and the less light passes through it. Low numbers are used for lighter tasks such as gas welding and brazing, while higher numbers are used for arc welding and arc cutting.
The number alone is not the whole story. The right shade depends on the process, the current and how bright the arc is, so always check the shade chart that comes with your helmet or filter, or ask our team to help you choose.
What is the difference between a filter lens and a cover lens?
The filter lens is the dark lens that actually protects your eyes from the arc. A cover lens is a clear, replaceable plate fitted in front of it (and sometimes behind it) to take the spatter, scratches and grime so the filter stays in good condition.
Cover lenses are not a substitute for a filter and are not dark. They are normally the part you replace most often, and they should be changed when they are scratched, pitted or hazy enough to hamper your view.
Can I carry on using a cracked, pitted or badly scratched lens?
No. A cracked, pitted or otherwise damaged filter or cover lens can reduce your vision and weaken the protection the helmet gives you, and a damaged filter may let harmful ultraviolet and infrared radiation reach your eyes. Helmet makers say to replace damaged lenses and cover plates straight away rather than carry on working.
Inspect your lenses before each job. Replace the cover lens as soon as it is scratched, cracked, pitted or covered in spatter, and replace the filter if it is cracked or damaged. Check the manual for the correct part.
Does an auto-darkening lens still protect my eyes when it is not darkened?
Yes. Auto-darkening filters are built with a permanent ultraviolet and infrared protective layer, so that protection is present in the light state and does not depend on the electronics or the battery. Makers state this in their data sheets.
That said, the lens must still darken properly when the arc strikes. Test it before welding, replace the battery or cell as the manual describes, and stop using the lens if it does not darken reliably, is damaged or flickers. Do not rely on a faulty lens.
What shade of lens is used for gas welding, brazing and flame cutting?
These processes use much lighter filters than arc welding. Gas welding, brazing and flame cutting use the lighter end of the shade scale, with the shade rising with the size of the flame or the oxygen flow, while arc welding and arc cutting use darker filters that rise with the current.
Use the shade given in the maker's chart or the welding filter standard for your task and flame size. Shade charts often allow the next lighter or darker shade within the recommended range if the conditions call for it, but do not go lighter just to see better.
How do I choose the right shade for arc welding?
The shade depends mainly on the process, the welding current and the brightness of the arc. Higher current and brighter processes need a darker lens, and the recommended shade range is set out in the shade charts supplied with filters and in the relevant standard.
Start from the maker's chart for your process and amperage rather than guessing. If you wear a helmet with a variable shade lens, set it within the range for your work. A lens that is too light is a risk to your eyes, so do not go lighter than the recommended range just to see better. Better lighting can help instead.