Need help with fogging a LED lens.

[ShineOnYouCrazyDiamond]

EagleTac has some nice new lights out and I just purchased a MX30L3 with the XHP50. This light is a pretty cool beast of light and some good throw for its size considering how big the LED is. Problem is that I could only find the Cool White version using a J4 binned cool XHP50.

Why let this stop me, right? I sourced a 4000K J2 binned XHP50 from Mouser and both arrived today.

As I was removing the cool LED I noticed something a bit odd. The surface of the silicone lens on the XHP50 was a bit smoked looking. I swapped in the neutral LED, noting that the lens was pretty clear and I could make out all 4 dies of the LED underneath.

Fired up the light and right away I noticed it - the dreaded cross shadow in the middle of the spot. Reminded me a bit of the MC-E days.

Now it's not terrible and I imagine outside you'd notice it even less, but I would like to do something about it.

So I am looking for recommendations on what I could use to etch/fog the top part of the silicon lens on the XHP50 just a bit. I was thinking acetone, but not sure if that would work. I was thinking some fine sandpaper but I'm afraid that might shred the lens rather than fog it.

Any thoughts on what would work?

 

[jonwkng]

Hi Sean,

Funny thing, I was just discussing regarding the beam artefacts of the XHP with Icarus over on the Homemade and Modding subforum.

Vinh has been lightly sanding the domes with apparently good effect. See here:-

http://www.candlepowerforums.com/vb/showthread.php?402993-The-Lounge&p=4818024&viewfull=1#post4818024

 

[m4a1usr]

I did a chemical "frosting" or dulling the dome on an XML EZ White for the same problem a couple years ago but for the life of me I cant remember which solvent I used? I always have Acetone, Toluene and MEK on hand and I know it was one of those three but its been so long it just not clear which one was used. However I do remember a comment by DataLED in one old thread regarding the same problem with an MCE and he stated what he had used to correct the issue. I tried doing a search but came up with nothing. Probably didn't use the correct keywords. But a PM to him might get the answer you want? Hopefully his memory is better than mine.

 

[ShineOnYouCrazyDiamond]

I don't think the MC-E chemical would work on the newer as that had a glass lens. Probably sulphuric acid would've etched that one.

I will ping Derek and see if he has any idea.

I'll post up a pic comparing the two lenses later on.

 

[Vortus]

I'd probably try a very light diffusion film on the light lens itself first just to see if it worked. Up close MCE had the cross, but past a certain point it went away unless using aspheric.

 

[NoNotAgain]

I don't think the MC-E chemical would work on the newer as that had a glass lens. Probably sulphuric acid would've etched that one.

I will ping Derek and see if he has any idea.

I'll post up a pic comparing the two lenses later on.

Sulfuric won't touch glass. Hydroflouric acid will etch glass and in short order. You have to neutralize it after exposure.

One other way to get a white film on top of the lens is to expose it to super glue vapors. Every time one of my RC field boxes had a tube go bad, everything inside the box was coated in a white film that was dam near impossible to remove.

 

[ShineOnYouCrazyDiamond]

Well I wasn't about to get involved with any chemicals you couldn't just get out of your cabinets anyway. I don't have the proper ventilation hoods or equipment to deal with the heavy duty stuff.

Thanks for the recommendation to take a look at Vinh's page there. I was able to take some 600 grit sandpaper and just a handful of rubs over the lens was plenty to put a thin diffuse surface on it. Re-installed the reflector and the beam looks perfect.

 

[davyro]

I'm an interior decorator by trade so i spend quite a lot of my time rubbing things down with various grades of sandpapers,for a really fine finish you could use the abrasive side of a kitchen sponge that you use to do the dishes & various other cleaning duties,these are much easier to control how fine a surface you'd want to abrade

 

[stephenk]

Use D-C-Fix (preferably applied on the inside of the lens). You can purchase it from a few CPF members in the Marketplace.

 

[ShineOnYouCrazyDiamond]

Curious - would the DC Fix be for the LED silicon lens or the actual glass lens of the flashlight? I'm not trying to diffuse the whole beam, just clear up the cross created by the 4 LEDs.

I was able to use Vinh's method with some 600-grit wet-dry sandpaper and I think it worked out very well. No more cross in the beam. I had to do it a few times as I didn't want to go too far the first time. The first time I blurred the cross but ended up with a dark spot in the dead center. The second time I went a little bit more and the spot evened out completely.

 

[bykfixer]

I'm an interior decorator by trade so i spend quite a lot of my time rubbing things down with various grades of sandpapers,for a really fine finish you could use the abrasive side of a kitchen sponge that you use to do the dishes & various other cleaning duties,these are much easier to control how fine a surface you'd want to abrade

Scotch Brite pads are awesome as well.

Then there's the super flexible sanding sponges finish carpenters use.

Or sanding disks from headlight restore kits...

 

[stephenk]

Curious - would the DC Fix be for the LED silicon lens or the actual glass lens of the flashlight? I'm not trying to diffuse the whole beam, just clear up the cross created by the 4 LEDs.

I was able to use Vinh's method with some 600-grit wet-dry sandpaper and I think it worked out very well. No more cross in the beam. I had to do it a few times as I didn't want to go too far the first time. The first time I blurred the cross but ended up with a dark spot in the dead center. The second time I went a little bit more and the spot evened out completely.

The D-C-Fix is generally applied to the inside of the glass lens, and smooths out the hotspot and any other beam artefacts, and makes the beam a bit floodier.

Anyway, it sounds like you found a solution that worked.