Sciencemadness Discussion Board

DIY black light

vibbzlab - 7-11-2019 at 17:07

I just made a DIY blacklight by sticking those purple and blue color on my flash light. I just want to know whether it will work on fluorescein instead of UV light . Only then I am intending on synthesising it.
People selling UV light damn expensive here .

Texium - 7-11-2019 at 17:22

You mean you just put a purple/blue filter on a regular flashlight? If that's what you did, it isn't going to work. A regular flashlight doesn't produce UV light. All you're doing with that is filtering out the rest of the visible spectrum besides the blue/purple.

Ubya - 7-11-2019 at 17:38

"People selling UV light damn expensive here "
go to ebay, you can get a UV light from china for less than $1.
what you did is just filtering everything but blue light, you did not make a blacklight

vibbzlab - 7-11-2019 at 17:41

Ok I will . Thanks for that

B(a)P - 7-11-2019 at 17:50

Search for germicidal globe. I would get something that plugs into mains. In my experience there is the odd fake battery operated UV torch out there.

mayko - 8-11-2019 at 07:07

aren't antibacterial UV bulbs are a bit more powerful & dangerous than the blacklight bulbs you use to make posters glow?

UV LEDs are relatively inexpensive, eg:
https://www.digikey.com/product-detail/en/marktech-optoelect...
Depending on your needs you could slap one into a simple circuit or even solder it in your flashlight.

Texium - 8-11-2019 at 07:23

Yes, germicidal lights are more dangerous because they produce shorter wavelength UV. That kind of power is necessary for applications like visualizing TLC plates though. A regular "black light" won't cut it for that. The best of both worlds is a mineral lamp that can be switched between short wave and long wave for different applications. Unfortunately those do tend to be on the more expensive side ($20-$60 online depending on the brand and quality).

B(a)P - 8-11-2019 at 11:43

They need to be used with the correct eye protection and in a well ventilated area due to the production of O3.

Twospoons - 8-11-2019 at 12:30

Peak absorption for fluorescein is in the blue region around 470nm, and in the UV under 300nm. You do not want to mess with UV under 300nm.

So in actual fact using a blue filter on a flashlight to illuminate fluorescein is a reasonable idea.

[Edited on 8-11-2019 by Twospoons]

[Edited on 8-11-2019 by Twospoons]

wg48temp9 - 8-11-2019 at 12:36

Quote: Originally posted by B(a)P  
They need to be used with the correct eye protection and in a well ventilated area due to the production of O3.


Not all germicidal lamps produce ozone.

From wiki: For most purposes, ozone production would be a detrimental side effect of lamp operation. To prevent this, most germicidal lamps are treated to absorb the 185 nm mercury emission line (which is the longest wavelength of mercury light which will ionize oxygen).

In some cases (such as water sanitization), ozone production is precisely the point. This requires specialized lamps which do not have the surface treatment.

rockyit98 - 8-11-2019 at 18:29

i got 1W UV led for 1$ .need 3.5 to 4v to work. good heat sink a Li-ion battery and you good to go.ware eye protection! good sun glass will do the trick.to be sure check the glasses by shining the light through it to something fluorescent.

nezza - 9-11-2019 at 00:30

Fluoresceins excitation wavelength is in the visible at about 480nm (Cyan) so you should get away with using a purple/blue filter on a flashlight. One thing to bear in mind is that the flurescein must be in neutral or alkaline solution. Acidic conditions kill the fluorescence.

[Edited on 9-11-2019 by nezza]

diddi - 9-11-2019 at 01:42

the 300nm UV light is rather expensive to set up, is hazardous to use without the correctly rated eye protection and cannot be reproduced with filters over a regular torch.

for UV-C which is the 250-300nm band, sunglasses will not provide any protection at all. even "100% UV filtering" or UV400 rated are n't any good.
the glasses must be ANSI Z87.1 complient to protect from short wave UV. if you only need very low power UVC search ebay for 254nm torch

Heptylene - 9-11-2019 at 13:50

You can get UV LEDs for several cents on ebay. Typically there are models from that produce 365 to 405 nm. Blacklight bulbs (UVA) produce 365 nm UV light. Germicidal lamps (UVC) produce 254 nm light.

Be very careful with high power UV LEDs (several watts), especially the 365 nm ones. They produce almost no visible light tricking you into thinking they are safe, but the UV output can be tremendous especially close the LED itself. You can reach UV light power densities (W/m2) 100x or even 1000x those you get from sunlight, meaning you can get sunburnt within seconds, or damage your eyes permanently.

vibbzlab - 11-11-2019 at 19:48

I'm really feeling bad on picking this post up again .But I tried buying 3 different UV light in the market vere , everything turned out to be fake ones. Can someone give a link to genuine UV light I can get economically to India?

Ubya - 12-11-2019 at 00:04

Quote: Originally posted by vibbzlab  
I'm really feeling bad on picking this post up again .But I tried buying 3 different UV light in the market vere , everything turned out to be fake ones. Can someone give a link to genuine UV light I can get economically to India?

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.eb...

i don't if it ships to india, but trying never harms.

Herr Haber - 12-11-2019 at 04:06

Quote: Originally posted by vibbzlab  
I'm really feeling bad on picking this post up again .But I tried buying 3 different UV light in the market vere , everything turned out to be fake ones. Can someone give a link to genuine UV light I can get economically to India?


I had to give it a few tries before getting a UV lamp that performed well.
Eventually I settled for a 18650 flashlight that has a UV mode (works well) and a spotlight of sorts.
This last one is connected to the mains and works beautifully.

IMG_2923.JPG - 51kB

diddi - 12-11-2019 at 13:10

@vibbzlab. what spec do you need for your UV? wattage / range / price range

[Edited on 12-11-2019 by diddi]

vibbzlab - 12-11-2019 at 16:06

I just need it for that fake note test and for demonstration of fluorescein

diddi - 12-11-2019 at 17:14

https://www.ebay.com/itm/Aquarium-Pond-UV-Bulbs-Steriliser-F...

here is an example if a bulb you could use to make a cheap UVC lamp :)

Note this will have visible light also. to make a true UVC lamp requires a fancy filter that will make the project VERY expensive.

[Edited on 13-11-2019 by diddi]

vibbzlab - 12-11-2019 at 17:31

I can't get it . It's not available in India. Anyway thanks for helping

vibbzlab - 15-11-2019 at 21:48

I just tried placing to cellophane tape which was colored purple and dark blue by permanent marker on top of my mobile flashlight and I got this with the fluorescein

IMG_20191114_183623.jpg - 2MB

vibbzlab - 16-11-2019 at 08:53

Thanks for everyone's help I could finish my video on properties of Resorcinol
https://youtu.be/8MBU7n_Zyw0