How Long Does Welders Flash Last?

Written By: Liam Bryant

Reviewed By: Russell Egan

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On average, a welder’s flash heals in 1-4 days with proper eye care. The cornea usually repairs itself without leaving scars. The healing period varies depending on several factors, such as the type of welding arc and protective gear used.

So, what happens when someone doesn’t take welding safety precautions? In that case, how long does welders’ flash last?

Continue reading this article to learn about welders’ flash and how long it lasts. I’ll also walk you through the common symptoms and treatments. Plus, I’ll discuss some preventive measures to protect yourself from a welder’s flash. Let’s get right into it!

What Is Welders Flash?

Welder’s flash, or photokeratitis, is like a sunburn but for the eyes. It happens when you directly look at ultraviolet (UV) light. 

Typically, the bright light causes inflammation in the front of the eyes, especially the cornea. The light can occasionally cause superficial burning to the mucous membranes that line the eyelids. 

It’s natural that the cornea—the transparent structure covering the colored part of the eyes—gets the most damage from UV light. 

That’s because the cornea acts as a windshield for the eyes. It’s responsible for protecting the inner structures of the eyes. Plus, it focuses the entered light on the retina to produce vision.

welders flash

Why Does UV Light Cause Welders Flash?

For those who don’t know, radiation can have different wavelengths. As a result, scientists classified light into seven types according to length. 

These radiations are radio waves, microwaves, infrared light, visible light, ultraviolet, X-rays, and gamma rays—starting from the longest wavelength to the shortest. 

The shorter the wavelength, the higher the light’s energy. And as you can see, the UV wavelength is shorter than visible light. 

So, it’s no surprise that it has a higher penetration power than visible light. Consequently, UV can cause tissue damage.

What Causes UV Light Radiation When Welding?

As you weld, metals get hot due to their thermal conductivity. That heat causes the electrons to jump to a higher energy level. However, that pump is only temporary. Soon, the electrons lose that energy in the form of radiation and return to their original place.

The hotter the metal, the shorter the wavelength it emits. As a result, the welding flames change from red to blue or violet the longer you weld. 

Now, it’s no surprise that welding reaches high enough temperatures to cause significant UV light emissions. The problem is that we can’t see UV light to avoid it. That’s why the flash you’re used to seeing in welding can suddenly cause eye irritation.

However, it’s not just welding that damages the eyes. Any source of UV light can cause corneal discomfort. These include the sun, bright lamps, lightning, plasma cutters, and cutting torches.

That’s why photokeratitis has many common names, including:

  • Arc-eye
  • Arc flash
  • Flash burns
  • UV burns
  • Snow blindness
  • Welder’s eyes

How Long Does Welders Flash Last?

While arc-eye can last as little as one day, it can cause complications like keratoconjunctivitis. Such eye problems can take a couple of weeks to treat. Usually, not wearing proper protective gear increases flash burn symptoms’ severity.

That said, several factors can determine how long a welder’s flash lasts, including:

  • The welding method
  • The type of base metals used in welding
  • The angle of UV emission

Let’s discuss each factor in detail.

The Welding Method

Not all welding processes produce the same amount of UV radiation. That depends on how hot the welding arc gets and its energy. 

Generally, MIG, TIG, and Stick welding produce high levels of UV light. The amount of UV emitted increases as you amp up the electric current. That makes sense since these types of arc welding reach high temperatures. 

Submerged and oxy-acetylene welding can produce minimal UV. So, they aren’t a concern compared to arc welding. As for resistance and friction welding, they don’t emit UV light.

The Type of Base Metal and Filler

The type of welded metal also affects the amount of UV emitted. Welding stainless steel, aluminum, and cast iron produce intense UV light. Not to mention, these metals are among the most common materials used in many industries.

Aside from the welded metal, filler components affect the harmful effects of UV radiation. For instance, rods with higher iron content, like E4916, give off more harmful UV radiation than those with nickel or chromium.

Magnesium-containing materials can produce hazardous UV radiation when welded with aluminum.

If you’re unfamiliar with what the E4916 electrode is and what the naming means, I think my article on the types of welding electrodes would be handy for you.

The Angle of UV Emission

Objects emit light in all directions. Interestingly, the direction in which you position your head while welding can impact the hazard of UV light. 

For example, receiving UV emissions at a 40-degree angle from the arc can be more harmful than at other angles. As a result, your eyes might get more damaged, causing longer welders’ flash symptoms.


You can experience arc-eye symptoms between 30 minutes and 12 hours after UV exposure. The length of UV exposure determines how quickly a welder’s eyes develop. Likewise, the longer you stay in UV light, the more troubling your symptoms might get.

Common signs of photokeratitis include:

  • Eye pain and burning
  • Redness and bloodshot eyes
  • Excessive tearing
  • Swelling
  • Sensitivity to light
  • Blurry vision and seeing halos
  • Gritty eyes

On rare occasions, some people might experience temporary vision loss and a change in vision colors. You may also get bacterial and viral infections if the flash burn results in eye scratches.


If you’re experiencing welder’s eyes, I’ve gathered a few steps you can do to help alleviate your symptoms:

  1. Go to a dark room.
  2. Wash your hands before removing contact lenses (in case you wear them).
  3. Keep your damaged eye closed to prevent bacteria and viruses from contaminating it.
  4. Place a clean gauze pad in cold water and put it on your eyes until it warms.
  5. Repeat the above process until the eye discomfort fades away.

That said, you should seek medical attention as fast as possible. Your eye doctor will examine your eyes to determine the extent of damage and prescribe adequate treatment

These include:

  • Dilating eye drops to relax eye muscles
  • Antibiotic drops or ointments to prevent bacterial infections
  • Painkillers 
  • Steroid drops to ease inflammation
  • Eye patches to shield your eyes from bright light


Welding prevention measures are vital to preventing welder’s eyes and other UV-related eye diseases.

Here are a few tips to help you prevent arc-eye:

  • Wear protective gear like safety goggles and a welding helmet.
  • Make sure the safety goggles have a shade number between 8 and 13.
  • Use shade number 14 eye protection for carbon and hydrogen arc welding. Likewise, wear shade 14 glasses when using shielded metal arc welding for thick metals.
  • Wear sunglasses outdoors whenever there’s bright light.


So, how long does welders’ flash last?

Typically, welders’ flash can fade within 1-4 days. However, your eyes can take weeks to heal from flash burn complications like keratoconjunctivitis. That’s especially true if you’ve been exposed to UV light for a long time.

Aside from exposure time, the type of welding process and the base and filler metals can affect the hazard of UV radiation. Plus, arc-eye risk depends on the UV emission angle when entering the eye. The former factors also determine how fast you develop flash burn symptoms.

Whether you’ve experienced a welder’s flash or not, always wear safety goggles and a welding helmet. That way, you can protect yourself from that eye-burning issue.