Luminosity of HID light without Blues and Greens?

[Sleazy E]

I am hoping this is an easy question. I just typed a really long thread and this forum slapped me in the face as I tried to submit it.
I have found some really good answers to questions in the past on this forum so I thought I'd seek help here.

My project consists of refurbishing the reflector bowls of some HID projectors. The original coating is a Vapor Deposited Aluminum, and like most of these applications they are burned in areas and not as reflective as I want them to be. (I bought them with the following purpose...)

I am building an Electroplating machine (For other hobbies too) and am looking to plate Gold onto the reflectors.

I'm wondering what color the light will be of a typical HID bulb if it is reflected by Gold (Au)?
I am also wondering if the luminosity will take a hit by the lack of blues and greens being reflected?

Here is a graph showing the wavelengths' reflected by Gold and a typical spectrum taken from a couple of fairly common HID bulbs...

I will be using a photometer to measure reflectance based off of the same light source using different coatings or materials. Different tests are to be conducted using the data yielded from a spectral reflection at a set distance to measure the lux.
My project will consist of "before and after" results from different reflector-bowl conditions/coatings and with other, popular cars with known projector/bulb/ballast options as a sort of independent variable to find comparable data.

[Diesel_Bomber]

Pretty simple. Less light reflected = less lumens.

I know the lumen difference between filtering out orange/red and filtering out blue is staggering with an incandescent bulb, but I know very little about HID's. Good luck, I'm interested. Keep in mind that some of the light will still be coming directly out from the bulb.

[Alaric Darconville]

An electroplate coating, compared to a vapor-deposited coating, will probably not yield very good results at all, regardless of how continuous the reflected spectrum is.

Silver might work better (although it's usually better for a secondary surface mirror than a primary surface mirror).

[Sleazy E]

An electroplate coating, compared to a vapor-deposited coating, will probably not yield very good results at all, regardless of how continuous the reflected spectrum is.

Silver might work better (although it's usually better for a secondary surface mirror than a primary surface mirror).

Thanks for the answers.
Alaric, why do you think an electroplated metal would fail in comparison to the VPD?
One thing to consider is how the production line for VPD is enormous to coat all of these bowls and on the cheap to save money. Now, those things are only speculation but not outof the question. The coating on the bowls I have is poor at best... orange peel, cloudiness, etc. It appears that a mirror-polished stainless steel would yield a better reflection!

[Sleazy E]

An electroplate coating, compared to a vapor-deposited coating, will probably not yield very good results at all, regardless of how continuous the reflected spectrum is.

From my research...
Ag, Au, Al, and NiFe (to name a few) will form the same texture when applied by either PVD or Electrodeposition. The crystal lattices that are formed created the same planes and so the final coating will be as sufficient if Aluminum were to be plated in a proper manner as compared to a PVD Aluminum. Chemical deposition is a worthless topic to cover as it is entirely different.

[Scheinwerfermann]

Interesting experiment. I concur that a Gold-electroplated reflector will probably be substantially inferior to the original aluminum. It's fun to build homebrew equipment, but in this case if the reflector bowls are fundamentally sound, just strip 'em and send to vacu-coat for remetalization with vapor-coat aluminum and appropriate topcoat.

[Sleazy E]

Thanks for the reference in VacuCoat. I sent them an email to request a quote on my items, and I'm looking forward to hearing back from them.

I still don't know why you guys think the plating will be less than sufficient?

[dmk9561]

I would put it at a combination of surface and color. Plating with gold will change brightness and color, which you admit you recognize. That alone is probably enough to make the lights non-compliant. Secondly, most of the responses don't seem to think that the surface texture of electroplated gold would be as smooth as the original aluminum. If the surface isn't mirror-smooth, the efficiency of the reflector would be far too low. The combination would be non-complaint, yellow headlights that would have a dim and unfocused beam. That just isn't safe to use.

[Hamilton Felix]

This thread struck a memory chord. A few times, I've seen fog lights that used gold colored reflectors to achieve their yellow (selective or otherwise), instead of the more common yellow lenses. I don't know how well it worked in practice, only that the light was not as obviously yellow when turned off. Maybe the gold plated reflector would be useful in fog lights. I can't help wondering if it would make a headlight suddenly look like a French headlight of the past. But for on-road use, other than maybe replating fog lights, I don't see it as a good idea.

[Scheinwerfermann]

Yes, there have been selective-yellow lamps where the color filter is in the anticorrosion overcoat over the aluminum reflector, rather than in (or around) the bulb or in the lens. It's just another way to do it. Gold would not cause a lamp to produce selective yellow light, it would be sort of...gold colored (or greenish, I suppose, with an HID light source)

[Sleazy E]

The following is not aggressive toward anyone, it may sound that way, though.

If the surface isn't mirror-smooth, the efficiency of the reflector would be far too low.

I had every intention of polishing the surface and also taking every precaution in doing the plating correctly. The order in which I'm researching each facet of this project is not so chronologically correct, per se, but I had already come to the realization that I may need to go with the original route of VPD (Al) if I found my research to not be worthwhile.

...most of the responses don't seem to think that the surface texture of electroplated gold would be as smooth as the original aluminum.

Take a look at any reflector bowl that has an aluminum coating, or better yet, the coating of an HID reflector bowl. I noticed right away that regardless of how super awesome and reflective the 'Al' is in this particular form of deposition that it would not matter one bit if the application was poor and the surface prep was poor. Now, one thing you may grasp is how much time the manufacturer put into prepping and the application of the deposition. I think their time is saved in many areas to prevent excessive cost in minute details. Orange peel, cloudiness, and burned coatings are how 90% of these bowls look after 5-10 years, so ANY reflective coating would fair better... even a bright nickel plate over a "mirror" surface that will yield 100% less defects than when the 'Al' coating came off of the showroom floor; which looks to have a reflection comparable to polished SS (~70% reflectivity) at BEST. Yes, it's still shiney and it still puts out a lot of light when you're around it but that is because those damned metal halide bulbs are SUPER bright.

[Alaric Darconville]

I had every intention of polishing the surface and also taking every precaution in doing the plating correctly. The order in which I'm researching each facet of this project is not so chronologically correct, per se, but I had already come to the realization that I may need to go with the original route of VPD (Al) if I found my research to not be worthwhile.

Despite the best preparation of the surface, electroplating will not result in the uniformity of coating that vapor-deposited aluminum will give, and nowhere near the 99% reflectivity of said aluminum coating (when undamaged). Part of it may be in the size of the molecules themselves; neutral gold atoms are pretty 'large', in a manner of speaking.

[Hilldweller]

Anyone remember my supplemental HID lights with yellow-tinted lenses?
With the 6000K bulbs, the light out of those looked pretty white. I think he'll just take the color down a few notches if he can get the reflectors shiney enough; maybe to 3500K or so.
It will certainly look pretty neat anyhow. I could see it catching on with the Escalade/spinner crowd too...

[Sleazy E]

Despite the best preparation of the surface, electroplating will not result in the uniformity of coating that vapor-deposited aluminum will give, and nowhere near the 99% reflectivity of said aluminum coating (when undamaged). Part of it may be in the size of the molecules themselves; neutral gold atoms are pretty 'large', in a manner of speaking.

Good point. I've also not heard of the reflectivity of aluminum being 99%, could you cite where you found that info?
Mylar has a reflectivity of near 98% but then again it's not easy to get it to form to curved parts.

Hill, you think the 6000k bulb would be dropped to around 3500? That's quite a deficit. Do you have any links to your HID setup or any pictures you could provide? What was used for the yellow in the tinting?

Escalde crowd huh? Hmmmmm. Ahaha

[Scheinwerfermann]

Good point. I've also not heard of the reflectivity of aluminum being 99%, could you cite where you found that info?

It's a pretty accurate figure; you have to dig deeply into the internal literature of the headlamp engineering community to source it. This ain't Wikipedia, so you will probably not be seeing an original source for the assertion. :-)

Mylar has a reflectivity of near 98% but then again it's not easy to get it to form to curved parts.

If by "not easy" we mean "impossible" in the context of a headlamp reflector, that's right.

you think the 6000k bulb would be dropped to around 3500?

Whenever we introduce a color filter into the optical system, color temperatures are no longer anything but a vague approximation. There's little point to using them for this discussion. Remember the 6000K HID bulbs produce substantially less light than the legal 4100K-4200K items.

[Optical Inferno]

Just a thought of something else that may occur...gold will reflect more IR energy as well. This may cause a little more heat to be reflected out of the system. I don't know if this will effect the overall output. All in all, a neat experiment.

[Hilldweller]

I tinted the lenses yellow following the links on Daniel Stern's site; it came out great and I found the HID light much easier on my eyes with the yellow than just the 6000K harsh blue-ish white.
The light doesn't appear yellow after the tint in this case unless you look at it side by side with another HID or LED light; it looks sorta halogen-white.

Like Sheinwerfermann said, you can only take wild-arsed guesses at the actual temperature.

I had a thread on CPF too.

[Sleazy E]

Alright! Thanks guys, I've taken a little absence from this project because you all have given me some food for thought.
I'm still moving forward with a new plating surface on the bowls but I'm not entirely set on my options. I'm going to use a lot of Nickel for my other projects so, I dunno, I'll post up a result in a couple months.

[Scheinwerfermann]

Er...you're not planning on using nickel as the final reflective material, are you? It's nowhere near reflective enough at about 45%.

[Sleazy E]

Bringing back from the dead.

I know it's been a while, but I figure I would update.

I've sourced 75% of my electroplating machine for $0. Only a couple more pieces are needed that I will be buying to accomplish a finished and attractive look. Estimated total dollars spent = $30. Beats 300-1000 for a machine that is TOO much for 90% of jobs.

Schein, I'm not going to use Ni as my final coating. Currently, silver looks to be the best option without considering its rising status as a commodity in the US market. I have begun researching a viable protective coating that will prevent tarnish and etc. without reducing clarity.

I am purchasing an Extech AE31 this week and will be recording data from different stages and processes that I am considering for the bowls.

I have found a company that is local who will plate in the materials that I have mentioned and I may save one of the bowls or get another one for their use to see how comparable their application process is to the application from my machine, and my hands.