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​Give your steel sunburn

Posted by Tom Swan on Mar 29th 2020

Give your steel sunburn

Visible Light consists of different frequencies of wavelengths that range from UV (300 to 400 nm) to Black light (400 to 450 nm) through to “white” light that contains - blue through red (400 to 700 nm) up through the Inferred range. Different wavelengths of light have different properties which when used properly can assist us in everyday tasks.

While all wavelengths exist simultaneously in nature, The Human eye is most adept in viewing the visible white light spectrum. Many animals do not see in color but see different parts of the visible light spectrum. Many animals see infrared light that human eyes do not see, however, many animals can not see light in the green or red wavelengths unless looking directly into the light source. Many hunters use Green light which projects well but is not detected by game. Red light is often used to read maps at night and is used by hunters, pilots and stargazers.

It is also used by the military to preserve night vision which is better than the traditional method of wearing an eyepatch. Pirates used to wear eye patches so when they boarded an enemy ship and went below decks, they could flip up the eye patch and one of their eyes would be adapted to the dim lighting below decks.

Blue light works well to follow blood trails because it illuminates the blood from the background. This also works with Blacklight and UV wavelengths. Any one that is old enough to remember the late 60’s and early 70’s probably remembers the flourcent posters and blacklight in everyone’s dorm rooms and bedrooms.

Old Technology can provide new uses. Several paint companies have taken advantage that certain pigments Fluoresces under Black and Blue light frequencies by adding them to paint. When the paint is used as a primer and you hit it with black light, the coating fluoresces. Any areas that do not Fluoresces are unpainted making it easy to find discontinuities or holidays. When the primer is coated with a regular, non-flourcent paint, missed areas or holidays show through the coatings.

Another use of UV light is to determine the presence of Hydrocarbons on a substrate prior to painting. Most Hydrocarbons fluoresce between 220 nm to 400 nm. Polycyclic aromatic hydrocarbons (PAHs) are highly fluorescent due to their molecular structure.

365nm is an ideal frequency to use because the light emitting diodes at this frequency are reasonably priced and put out enough light to preform the task well. This frequency is also the same frequency used for NDT testing and several manufactures make lights that work well.

When looking for oil note that UV light will not detect straight-chain hydrocarbons such as mineral oils or synthetic oils such as many silicon based cutting oils.

MTest has several different options for UV lights. As an Acebeam distributor, we have worked with Acebeam to develop a new flashlight. The X80 light is the size of a soda can, puts out up to 25000 lumens of white light and has red, green, blue and UV diodes. We have worked with Acebeam to remove the colored diodes and replace them with 365 nm diodes. As a result, we have a floodlight that puts out a tremendous amount of UV light over a wide area and is one of the brightest white light and UV flashlights on the market.

Other excellent options are the Western Instruments SPR365-UV which exceeds all NDT standards for UV light. This light is a spotlight and puts out an intense focused beam of UV light. For those of you that need Explosionproof lighting we offer the EPL-UV-20W-G2 which puts out 1200 lumens of white light or with the 365 nm cutoff filter give out enough UV to hit a target at 200 ft.

While UV light does not look bright because the “white light” is not present, UV light can cause severe eye damage without you being aware that is happening. It should be important to note that even the UV reflecting off the surface of the steel can cause eye damage, so it is always recommended to wear UV protective glasses when operating the lights. They are in expensive and you can get them from $10.00 and up.

As a word of caution, this is the same type of light used by forensic experts to look for blood and other bodily fluids, so it is generally not recommended to use them in your hotel room or you may never sleep in one again.