How Bright Is The Welding Arc Compared To The Sun?

The Sun is undoubtedly the brightest thing in the world, and its comparison with a welding arc seems foolish at first sight. However, some interesting facts made people ask questions like: How bright is the welding arc compared to the sun? And, Is the welding arc brighter than the sun?

Of course, the sun is brighter than the welding arc or any other thing in this world, but what made this comparison possible is the level of effect on human health by the welding arc.You can look at the sun directly with bare eyes. Although it is an unhealthy thing to do, it is a fact that you can do it without damaging your eyes instantly.

However, looking at the welding arc without professional protective gear, you get a physical jolt through your body. High-intensity photons will instantly strike your optic nerve, making you completely blind for a few minutes. This is a painful experience; damage could be severe, prolonged, or even permanent. Therefore you should never try this.

I have summarized some interesting facts and figures in this article to make this comparison simple and understandable.

How Bright Is The Welding Arc Compared To The Sun?

To measure the brightness of the welding arc compared to the sun, we need to consider a few scales like heat, intensity, luminosity, and radiation.


The sun’s temperature is 5800K, the hottest temperature in the world. The temperature of welding arcs ranges between 3400K-3800K, almost to that of the sun.

The temperature of the welding arc is kept that high to melt the metals and then join them. However, the sun’s temperature is almost twice that of the welding arc, and we cannot achieve this temperature on earth.

Another factor we need to consider is the radiated heat. Of course, the sun’s radiated heat is also greater than the welding arc.

Intensity and Luminosity

According to a rough estimate, the intensity of a welding arc at a distance of a half meter or 20 inches is around 1000 W^m2, while at 1 meter, the intensity level remains at about half of it, but with a larger portion of shorter wavelength radiations.

On the other hand, the sun intensity level is around 1000 W^m2 at the latitude at noon in the summer months. So the intensity of earth forms 151. 48 million km is almost the same as the intensity of an arc from a distance 0f 0.5 meters. So these figures reveal that the sun is much brighter than the welding arc.

Although a small wedding arch is not as bright as the sun, it is highly intense for its small size. Now, let’s move to the second part of the problem: if the Sun is brighter than the welding arc, why does the welding arc impact our physical health?


Sun is about 152.48 million km from the earth, and therefore, the radiated heat and luminance that reaches the earth is a very small portion of what is produced by the sun.

On the other hand, a welder is exposed to the radiated heat from a welding arc from a short distance. Therefore it has a more severe impact on the human body than on the earth.

High energy photons directly hit the optical nerves from a shorter distance causing severe pain and damage to the eyes.


We are blessed with an atmosphere that filters the solar radiation before they reach the earth-thanks to nature. The harmful ultraviolet rays are blocked in the atmosphere, and only a small portion of harmful rays reaches our earth.

In contrast, the welders are exposed to a shorter wavelength since there is no filtration medium between them and the welding arc.

UV Rays and Welding Arcs

Ultraviolet radiation has a shorter wavelength than visible rays. We know that welding arcs emit intense infrared, visible, and UV traditions. UV rays emitted from the welding arcs can cause vision problems, blindness, cancer, and other chronic diseases to the welders.

There are three types of UV rays, UVA, UVB, and UVC. Both metal arc welding and plasma welding emit all three types of UV radiation. Most of the UV rays coming from the welding arc are UVA, but thankfully it’s not harmful to human health.

UVB and UVC rays have a small portion of the spectrum but are extremely dangerous. 95% UVB and 100% UVC rays from the sun are blocked in the atmosphere.

But this is not the case with witty welding arcs. The UVB and UVC rays are absorbed in the cornea if the welder is not welding the protective gear.

Also, they can damage the skin, and prolonged exposure can cause skin cancer. Here are the major problems associated with the intensity and UV traditions of the welding arcs.

Effects of UV Rays on Health

Below three I have discussed the three main health effects UV rays contain.

UV Rays and Welding Arcs
Side Effects of UV Rays and Remedies

Arc Eye Or Welder Eye

Arc eye is the common name for the eye disorder conjunctivitis. UVB and UVC rays emitted by ARC welder can damage the eye’s mucous membrane. The initial symptoms of this disorder include the feeling of ‘sand in the eye’ and mild pain.

However, with prolonged exposure to radiation, the symptoms become more severe, including redness in the eye or even bloodshot, poor eyesight, inability to look at the light sources, and highly sensitive eyes.

You are at risk if you are a welder or do any other job in the welding workshop. You should wear a welder’s helmet with a fitted filter sheet. Additionally, you should wear protective goggles and eye shields to protect your eyes from harmful UV radiation.

Skin Cancer

Welders are at increased risk of skin cancer, says International Agency For Research On Cancer. The UVA and UVB rays are mutagenic and carcinogenic and can cause skin cancer, especially when the body is exposed to them without any protective gear.

You can only reduce the risk of skin cancer in welders by following the safety data sheets and safety protocols at the workplace. Proper materials, controlled reactions, and protective gear reduce welders’ skin cancer risk.


The temperature of the welding arc could be as high as 3400K, which is enough to melt metal. If not handled with care, the welding arc can cause a serious burn that may cause death.

Following all the safety protocols at the workplace is the only solution to avoid burn injuries. However, human error exists, and you should seek immediate medical help in case of workplace accidents.

How Many Lux Is a Welding Arc?

The brightness or luminance of a welding arc can vary depending on the specific welding process, the type of electrode or filler metal being used, the welding current, and the welding environment. However, welding arcs generally can be very bright and emit very high levels of light.

The brightness of a welding arc is typically measured in terms of its luminous intensity, expressed in candelas (cd). The illuminance, or the amount of light falling on a surface, is measured in lux (lx) and depends on the distance from the light source.

According to the American Welding Society, the luminous intensity of a welding arc can range from 2,000 to 20,000 candelas per square meter (cd/m²) or more, depending on the welding process and conditions. However, the illuminance of a welding arc at a typical working distance (around 12 inches or 30 cm) is typically much higher than what most light meters can measure accurately and can exceed 1,000,000 lux (lx) or more.

It is important to use appropriate eye and skin protection when welding to avoid damage from the intense light and UV radiation emitted by the welding arc.

Wrapping Up

Sun is a real winner of the Sun Vs. Welding Arc brightness competition. But answering the question, How bright is a welding arc compared to the sun, I realized that a welding arc is not an underdog either.

A small welding arc is bright, hot, and intense enough to impact human health hugely. Shorter distance and the absence of any filter medium intensify their impact on human health. Therefore it is critical to wear professional safety gear at the workplace and follow all the safety protocols.

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Dave Walker is a skilled welder and passionate blogger. With years of experience in welding, he has honed his craft and developed a deep understanding of the trade. In his blog, he shares his experiences, insights, and tips on welding, offering a valuable resource for fellow welders and those interested in the field. He is dedicated to promoting the importance of welding and its applications in various industries.