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HOW-TO-TEST UV BLACK LIGHTS

 There are several different types and as many different qualities of UV Black light units on the market. Generally speaking they fall into 3 main types:

Mercury Vapour Lamp - Used in large UV Projectors such a UV Canon and a UV Flood.

UV Fluorescent Tube or Bulb - Most widely used form of affordable Black light.

UV LED based units - LED Torch or Flashlight versions.

 

The Holy-Grail of UV lighting is to produce  a pure 365nm UV output with Zero Visible Light Interference. As this is not yet practical (or affordable), so let price be your guide as to how close your choice of UV light will come to achieving this. 

 

Remember:  The more visible light you see, the worse the UV quality will probably be.

For most applications a certain amount of visible UV glare is acceptable which makes the basic UV units affordable. 

Fluorescent tube based black lights generally produce the best results when compare with LED based alternatives. However, they only offer a short effective working range (illumination distance) and require mains-powered operation to deliver their best results, both of which limits their use and practicality. 

LED torches and Flashlights generally produce a strong 'UV beam' best suited to illuminate 'at a distance' and are not usually suited to close-up work, owing to the higher visible-light 'interference' output, which tends to mask (or suffocate) the resulting fluorescence.

Higher Quality Forensic Torch with a lower visible output, may be used for both close-up and distance work

Let price be your guide and do not buy cheap UV LED torches expecting good results!

Remember - Lots of visible 'Purple light' is usually an indicator of POOR UV Quality!

The simple test below will enable you to find out into which frequency band your UV Torch belongs...

 

 

bUV LED Products Fall Into 3 Categories

 

1. POOR QUALITY  (Frequency Range: 390 - 405nm)

Torches operating in the wider 390nm - 405nm range generally use poor quality 'cheap' UV LEDs which produce far too much unwanted visible 'purple glare' (interference) and far too little in the way of a useful UV light. 

A general rule-of-thumb is the more LEDs the torch has, the lower the Quality of UV produced.  Avoid torches with more than 9 UV LEDs.

 


 

2. GOOD QUALITY  (Frequency Range: 380 - 385nm)

Torches outputting UV in the 380nm range perform much better and produce superior results, with a much reduced 'visible' (interference) output. Such units will naturally be more expensive than the cheaper 390-405nm models.  Click here

 


 

3. HIGH QUALITY  (Frequency Range:  365 - 375nm)

By stark contrast, the higher quality, more expensive torches producing the 365nm wavelength, produce a near pure UV output which is the optimum frequency for UV fluorescence. This means you will see far more detail and in a greater range of colours than any other wavelength.  As these units generate less unwanted Interference light, they may naturally appear weaker or darker. This can be misleading and should not be misinterpreted.  

 


 

 

The example shown below uses Invisible UV Contact Powders which require UV light to reveal their UV 'glow' colour. The powders are a neutral 'white' colour in ordinary light.  Move your mouse over an image to see the normal colour.

 

Poor Good Best
390-405nm 380-385nm 365-375nm

 

As you can see from this example, the best colour generation and brightness comes from the 365nm UV Light.

 

 

Try this simple test...

 

In this following demonstration, which use a British £20 note, it is possible to see the differences between the wavelengths and to demonstrate a simple and effective way of testing or determining, the operating wavelength of a UV LED Torch or UV Lamp.

 

 

UNDER NORMAL LIGHT

Under normal light there should be NO UV fluorescence visible to the naked eye.

 

 
 

UNDER POOR QUALITY UV

Shown using a 'Cheap' 390-405nm UV LED Black light Torch

Far too much visible violet light (interference) produced due poor quality UV LEDs thus producing a poor quality result, with much of any fluorescence generated masked by the visible purple glare. 

Many people mistakenly believe that a bright purple 'visible' beam means a high UV performance.  The reverse in actually the case and the visible purple glare is an unwanted bi-product resulting from poor quality UV LEDs!

 

 

 

 

UNDER GOOD QUALITY UV

Shown Using a Forensic 380-385nm UV LED Blacklight Torch

 

This range produces a much higher quality of UV light with very little purple glare; rather a cleaner, softer, whiter light that allows a greater range of fluorescence to show through. Notice the Red/Yellow '20' and the little multiple fibres that are now revealed under a high quality UV light source.

 

 

 

UNDER HIGH QUALITY UV

Shown Using a 365-375nm UV Lamp

 

These 'Professional' UV Lamps produce a Very High Quality UV source at 365nm; the optimum frequency for fluorescence. Very little visible light is produced to mask or interfere with the resulting fluorescence. Notice that with this 'pure' UV frequency the '20' and fibres are much brighter than with any other frequency.

 

 

Beware of cheap, poor quality imitations.

If it doesn't bear our name, it's not the same!

 

 

Which kinds of UV light are safe?  Click here to read more

 

 
     
 

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