How Bright is a Welding Arc Compared to the Sun?

Welding arcs can be unbelievably hot and bright. In fact, they’re so hot that you can’t help but wonder if this is what hellfire feels like.

No welder can deal with an arc without some serious protective gear, especially for the eyes. A welding arc (especially at night) might look as bright as the sun, but is it, though?

So how bright is a welding arc compared to the sun? A welding arc is not brighter than the sun, no matter how bright it may seem to you.

Welding arcs are bright and produce a lot of heat. Welding produces around 3400 K of heat, whereas the sun produces 5800 K.

If we were to measure brightness through radiated heat, then the sun is the undisputed winner in this battle. Radiated heat is directly proportional to the fourth power of an object’s absolute temperature, so the sun is about 8.4 times brighter.

Now, remember that the sun is nowhere near us. It is a lot bigger than the Earth and thankfully, a lot further away.

The distance makes it easier for us to look at it (though you should never look directly at the sun).

The luminosity of the sun

Luminosity is the amount of light emitted by an object in a unit of time. It is an absolute measurement. This does not vary with the observer’s distance from the object.

The luminosity of the sun is 3.846 x 1026 watts. This is so bright that astronomers even measure the luminosity of other objects in terms of the sun’s luminosity.

Radiation in arc welding due to brightness (and the risks to be aware of)

So we know that welding arc doesn’t come close to being as bright as the sun.

Welding arcs are incredibly bright, though. They even produce harmful UV radiation, making protection is necessary.

Welding arcs release a significant amount of UV radiation. A metal inert gas weld using helium at 300 A usually produces around 5Wm-2 UVB and UVC radiation at a distance of one meter.

The sun at noon, in comparison, produces less radiation.

What are UVC, UVB, and UVA radiation?

Welding arcs give off UV radiation, visible light, and infrared radiation. There are three types of UV rays based on their wavelengths: UVA (315 to 400 nm), UVB (280 to 315 nm), and UVC (100 to 280 nm).

UVC is short wavelength radiation. It is the most harmful UV radiation emitted by the sun.

It is filtered through the atmosphere and does not reach the Earth. However, UVC radiation produced through welding can cause significant harm.

UVB is medium wavelength UV radiation. It is very active but cannot penetrate through the layers of the skin.

It produces a lot of harmful effects like skin aging, delayed tanning, and burning. It also promotes the development of skin cancer, making it a very dangerous form of radiation.

The atmosphere blocks most of the UVB radiation produced by the sun. However, UVB produced by welding can reach and affect humans.

About 95% of the UV radiation reaching the Earth is UVA radiation. It has a relatively long wavelength and can penetrate deep into the skin.

UVA radiation is responsible for skin tanning and contributes to skin aging and wrinkling. Recent studies have also shown that UVA rays can contribute to the development of skin cancer.

UVA radiation also passes through the cornea and can be absorbed through the lens of the eye.

What is arc eye?

The UV radiation produced by welding equipment can damage the surface and mucous membrane of the eye. The damage is referred to as ‘arc eye,’ ‘welders eye,’ or ‘arc flash.’

Another common name for arc eye is conjunctivitis, which is the inflammation of the mucous membrane of the eye.

The symptoms of ‘arc eye’ include:

  • Pain in the eye
  • Tearing and reddening of the eye and the membranes surrounding the eye
  • A sensation that feels like there’s sand in the eye
  • Sensitivity to light
  • Photophobia

The intensity of the UV radiation, the distance from the welding arc, the angle at which the radiation enters the eye, and the type of eye protection all significantly affect the amount of time it takes for a person to get arc eye.

Long term UV radiation heats the lens of the eye. The overheating of this lens can produce cataracts.

Visible light from a welding arc can cause temporary blinding and eye fatigue. The light emitted is so bright that the iris of the eye does not find sufficient time to close and limit the light reaching the retina. Over time, this can create severe problems for the welder.

Skin hazards due to UV radiation

Arc welding produces the full spectrum of UV radiation. The short distance between the welder and the welding arc is not enough to protect the skin.

UVB and UVC radiation may penetrate the skin, putting the welder at serious risk of developing skin cancer.

Furthermore, exposed skin is prone to tanning and burning in the vicinity of a welding arc. Most welders find protective clothing an obstruction in the process.

Even though they are trained specialists, they sometimes overlook safety requirements.

Safety recommendations to prevent UV radiation in welding

  • Wear a full-spectrum sunblock that covers all forms of UV radiation
  • Always wear safety glasses, shoes, gloves, helmets and leather clothing
  • Ensure all protective gear, especially headgear, is UV radiation-proof
  • Put up screens or curtains to protect bystanders
  • All bystanders should also wear protective eyewear
  • Welders should receive regular dermatological hazards training

UV radiation is a known risk factor for skin cancer. In certain occupations, like welding, workers are exposed to non-solar sources of UV radiation. The exposure leads to an increased risk of skin cancer.

UVR from welding increases ocular melanoma. Welders and workers with a history of high exposure to UV radiation should visit their eye specialist for regular checkups.

Types of welding helmets to mitigate UV radiation

Different types of welding processes require different kinds of helmets. MIG welding requires helmets with #10 lens darkening, and TIG welding requires #11 lens darkening.

Here are some of the other helmets that offer UV radiation protection for welders.

Passive welding helmets

Passive Welding Helmet, Black, Classic MP-10, 8 to 12 Lens Shade

Passive welding helmets are the most generic form of welding helmets. It does not have a lot of fancy features, but it is built well.

It protects its user from ultraviolet rays, flying objects, and excessive heat generated during welding. It is an excellent low budget option.

Auto-darkening welding helmets

Antra Wide Shade Range 4/5-9/9-13 Auto Darkening Welding Helmet AH6-260-0000 Engineered for TIG MIG/MAG MMA Plasma Grinding, Solar-Lithium Dual Power, 6+1 Extra Lens Covers

During welding, the lens has to be adjusted accordingly to the amount of light being emitted. In a passive helmet, the welder has to do this manually, which can be very distracting.

In an auto-darkening helmet, the lens detects the amount of light it is receiving and switches up or down automatically.

Solar-powered lens helmet

Welding Helmet Auto Darkening Solar Powered Professional Welding Mask (980E Blue)

Some auto-darkening helmets operate via a solar-powered battery.

Solar helmets prove very economical as the battery only starts the helmet. Solar energy powers the rest of the functions.

A drawback of this helmet is that it is not ready to use. It needs to be placed in the sun for 24 hours before the project.

Battery-powered helmets

Tanox Auto Darkening Solar Powered Welding Helmet ADF-206U(USA POWER): Shade Lens, Tig Mig MMA, Adjustable Range 4/9-13, Grinding 0000, Plus 16 Inch Kevlar Fire Retardant Welding Gloves

These helmets use a lithium powered battery that can either be recharged or replaced. Welders often opt for welding helmets that are ready-to-use and automatic, since changing the lens manually is quite the hassle.

Fixed shade lens welding helmet

Jackson Safety Welding Helmet, 14975 - Comfortable, Durable Protective Welder Face Mask for Men and Women, Fixed Shade, Hard Hat Adaptable, HSL-100 Shell, Universal Size, Black

A fixed shade helmet comes with a set lens shade level – it’s usually set at 10. Fixed shade helmets don’t adjust according to arc brightness.

If the helmet does not provide optimal coverage from the arc, a welder’s chances of getting arc eye increase.

This helmet is ideal for DIY welders. It is an excellent choice for small welding tasks, like fixing the iron railing of the house.

It is not an ideal choice for professional welding jobs where the arc brightness may increase significantly.

Variable shade lens welding helmet

JSungo Welding Helmet Solar Powered, Luminous Auto Darkening Weld Hood with An Extra Clear Lens, Variable Shade Range 4/9-13 for TIG MIG Arc Welder Mask (Spider)

Welders who tend to work on various projects prefer this helmet. Unlike fixed shade lens helmets, the lens in this helmet adapts to different arc brightness levels and adjusts accordingly.

Most variable shade lens helmets vary from shade 9 to shade 13.

If you’re using different welding processes (Stick, MIG, and TIG) or varying welding amperage, the brightness of the arc will change. Variable lens helmets are the optimal choice for such procedures.

Related questions

Is welding hotter than the sun?

In terms of feel, yes, welding is hotter than the sun. However, this is only because the welder is in such close proximity to the heat source.

If the judgment parameters for both these questions were fair, and the heat produced by the two was judged from an equal distance, the heat of the sun would blow the heat generated from welding straight out of the water!

Is a welding arc brighter than the sun?

Even though a welding arc is not brighter than the sun, it is bright enough to cause considerable damage to the eye because of how close it is to a welder’s eyes. If you were this close to the sun, you would be burned to a crisp long before you had to worry about eye damage.

Welding arcs also produces a lot of radiation and are harmful to the skin. So, let’s skip the ‘how bright is a welding arc’ bit and focus on staying safe, no matter what.

If welding arcs are brighter than the sun, why don’t we use welding helmets to view solar eclipses?

There are mixed reviews about using welding helmets to view eclipses. According to some sources, NASA approves the use of a shade 14 lens for eclipses.

No matter what helmet you chose, make sure it meets the ANSZI Z87.1 – 2003 (also known as ANSI Z87+) standards. The ANSI standard is an indication that the helmet has passed independent testing for safety measures.

It judges them on their ability to protect against high velocity flying objects as well as UV radiation.

All helmets that have passed through this standard provide 100% UV and infrared filtering regardless of the shade setting. The standard also tests whether the helmet delivers advertised switching speeds in low and high temperatures as some helmets take time to switch shades in low temperatures.