Remove coating from blue bulbs?

[John_Galt]

Is there any way to strip the blue coating from these bulbs? The blue band over the highbeam on the H4 offerings appears to be Very dark on the new Philips +200.

 

[-Virgil-]

I have seen previously-coated bulbs successfully stripped without causing problems, but I don't know how it was done. The guy who did it was very tightlipped about his process, and he seems to have fallen off planet Earth (or maybe just died). But the answer to your question is yes, it can be done...somehow!

 

[John_Galt]

-Virgil-
I asked a budding chemist friend of mine what might be a good solvent to start with for glass and quartz that woukd see extreme heat (though not while dipped). His go-to, as usual, was acetone. I have several leftover/spare non burned philips xtremevision +130's from over the last few years, I think I'll give it a shot and report back.

 

[-Virgil-]

I tried acetone, the bulb almost laughed out loud about it. I think it would probably require much more aggressive chemistry, probably with a proper fume hood and full protective gear.

 

[jzchen]

Did you try ethanol or methanol?

 

[Travler]

Butanone AKA MEK Methyl Ethyl Ketone?

 

[Alaric Darconville]

Maybe he took a cue from Osram and used laser ablation.

 

[Travler]

Maybe he took a cue from Osram and used laser ablation.

I think it that use it was used on the reflective surface for dimensional accuracy. The blue band may have been done with plasma depositing process like is done to coat tool steels and wearing surfaces. If that is the case then no solvents can be used. It would take a multi step aggressive abrasion removal and repolishing.

 

[-Virgil-]

Did you try ethanol or methanol?

Yes, both of those had the predictable zero effect. Same with carburetor cleaner, brake cleaner, etc. We're talking about a coating that withstands extremely high temperatures on a completely nonporous, completely smooth material. Stuff we have under the kitchen sink or on the garage shelf isn't going to remove it.

 

[Alaric Darconville]

I think it that use it was used on the reflective surface for dimensional accuracy.

What reflective surface? There's no functional reflective surface in/on an automotive halogen bulb. Osram is using the laser to burn a specifically-shaped window in the blue coating.

 

[John_Galt]

Sounds like I need to invest in some frikkin La-Zers, perhapa Dr. Evil has some he's willing to let go.

 

[Lynx_Arc]

I wonder if TCE can do the job

 

[Alaric Darconville]

Sounds like I need to invest in some frikkin La-Zers

It will probably take supervillain money to get one up to the task, it definitely won't be the kind you find on DealExtreme. That kind of power surely doesn't come cheap. (Probably won't need One. Million. Dollars. either.)

I wonder if TCE can do the job

Probably not, and it's not worth the groundwater contamination and potential health effects playing with it.

 

[XeRay]

What about scraping it off with a NEW razor blade ? That works to remove the dark bands present on D2R and D1R that are not on D1S or D2S HID bulbs.

 

[Alaric Darconville]

The coating is way too thin for a razor to work. Laser ablation is the way to go.

Remember, the coating on those bulbs is designed to withstand repeated thermal cycling without flaking off, and without generating hotspots that can result in the envelope bubbling or cracking. It is also designed to be non-reactive (particularly, non-oxidizing) as the high-heat environment in a headlamp would otherwise mean rapid deterioration of the coating. If not bad for the bulb directly, then bad for the headlamp.