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The Frequency of UV Blacklights




There are many different types and as many different qualities of UV Blacklight units on the market. Generally speaking they fall into two types; UV Fluorescent Tube or UV LED based units.

With the exception of cheap, sub-standard units, fluorescent tube based blacklights are generally consistent in the quality of UV light emitted. However the vast majority of UV LED based blacklights (torches) being sold today are very poor quality units barely able to come close to emitting the required frequency of light. 

The Holy-Grail of a UV lighting unit is too produce Zero Visible Light with 100% 365nm UV Output.  This not yet possible (or affordable) but let price be your guide to how close your choice of UV light will come to this. 

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

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

We have come up with a very simply way of checking the frequency range  (UV Quality) of UV LED Torches.  The images below clearly show how the quality of light varies between the different classes of Torch.  Torches may look identical on the screen but performance and quality can vary hugely.



UV Blacklights come in 3 Main Frequency Ranges:



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' and far too little in the way of a useful UV light. 

TIP:  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.


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

UV Torches outputting in the 380nm range perform much better and produce far superior results, with a much reduced 'visible' output. Such units will naturally be more expensive than the cheaper 39-405nm models. 

Our UV Forensic Torch belongs to this class.


3. BEST 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. 

Both the Wash & Glow Checkpoint Lamp and UV Handheld Lamp belong to this class.



The example below uses Invisible UV GERM Powders which require UV light to show their 'glow' colour. The powders are a neutral white colour whilst 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, the best colour generation and brightness comes from the 365 - 375nm Frequency of UV Light.





Try This Simple Test...

The example below use a £20 GBP note (UV  is normally used to check for counterfeit currency) it is possible to see the differences between the wavelengths, and demonstrate a simple and effective way of testing / determining the operating wavelength of a UV LED Torch or UV Lamp.




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






Shown Using a 'Cheap' 390-405nm UV LED Blacklight Torch

Far too much visible light interference is emitted due poor quality UV LEDs thus producing a poor quality result, with 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 biproduct of poor quality LEDs.  As you can see from this example, the result is effectively worthless in this kind of critical application.





Shown Using a Forensic 380nm UV LED Blacklight Torch

This range produces a much higher quality 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.





Shown Using 365-375nm Checkpoint / UV Lamp

These more '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.





WASH & GLOW UV PRO Forensic Torch

Polished Steel Cased 9 x UV-LED Torch @ 380nm with our unique UV PRO Filter which removes 95% of visible (interference) light for a cleaner high quality result.



Beware of cheap, poor quality imitations.

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


 click here  

To see our range of UV Blacklights.



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