Is aluminum shinier than steel when polished?

What do you want to reflect, Michael?

light, sound, radio?

Aluminium will (with ease) provide an ultimately higher polish (barring scratches) but will be overkill in most applications - unless you are wanting to focus a light beam. (What is a standard mirror made of?)

Steel will rust, aluminium will oxidise. Chrome plate is sounding good.

-- Jeff

Aluminium then. ...but it will need periodic re-polishing with "Brasso" or something similar.

You just having fun, or is there some real application brewing here?

-- Jeff

Basically I wanted to know if I could make this:

look like this:

Coooooool. You get many B-17s flying over your place?

Have fun with it.

Yepper, you should go with the aluminum, if only because the steel will oxidize rapidly.

Loved the link to the light project though. Is that a high pressure Xenon arc lamp?

Jim

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I was gonna say, if he builds one of those the FAA will want to have a chat with him in short order....

Jim

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i got an aluminum door plate like most people.. i use brasso on it sometimes and it get pretty bright, like chrome, but in two days its very dull, but clean looking.. so i guess you gotta put some clear coat on it to stop it from oxidizing....

Aluminum polishes better but will oxidize. You must clear coat it.

As an alternative, how about polishing the substrate to the correct parabola then coating it with Aluminum? That's the way telescope mirrors are made.

Finding a vacuum chamber large enough may be a challenge though. If your parabola doesn't need to be as precise as a telescope, perhaps you could make it in several "pie" sections to be coated.

There is a reflective mylar film available you likely could easily laminate using some vacuum forming technique.

Commonly used for solar collection...basically opposite the function of your proposed project.

Wonder how large a chrome item can be ? That might be best.

Martin

Why don't you find and buy one of the originals and get it into serviceable condition, rather than reinvent the wheel? Or at least copy the original - Brass reflector, Rhodium plated...

Sperry / General Electric searchlight unit. The originals had servo-motos slaved to anti-aircraft guns.

You could stick with the Xenon Arc lamp, but carbon arcs are more of a challenge. I know someone who drives an old Strong Gladiator follow-spot with a 7KW carbon arc lamp.

-->--

My 6 inch telescope has an aluminium coated mirror. It's said to be slighlty less effiicient than a silver coated version. Ten years on, it's still highly reflective, and not close to needing a re-coat.

Also I have on my desk a desk tidy machined from a solid aluminium billet in an aircraft factory, engraved and buffed to a very high polish - very close to chrome like finish -. That was in 1987. It tooks years for the finish to fade.

Just a couple of reasons why aluminium is good enough and doesn't need coating with anything. Just don't eat lunch off it and keep it dry!

Steve

The reflectivity of metals from memory goes something like the following. Sliver 98% , Aluminum 92% , & chrome 50%. I'm sure steel would be lower than 50%.

When working on pools in the summer I get a bucket and scoop water out of the pool just to cool down the chrome wrenches. Its amazing how such a nice shiny tool can get so hot.

From the pictures it looks like they missed the focal point , look at how it's lighting up the buildings around it.

I like the idea of finding an old search light , that would probably be easy and cheap in a place like Vegas.

I recommend SimiChrome polish, available at many motorcycle shops. From Happich, Germany, I believe. It does a wonderful job of making aluminum alloy engine casings look like chrome. There are some cheaper alternatives for large area polishing, but I don't have brand names.

ac

I think that has the lamp mounted on two translators, so they can both steer and focus the beam while it's lit. Cute.

Jim

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The aluminum will be a lot better. Steel is about 50% with the big loss in the red end of the spectrum (steel looks a bit blue) while aluminum is pretty even across the visible spectrum and reflects about 92% of the light. You will want to overcoat with a thin layer of lacquer to keep the aluminum shiny. Optical mirrors are overcoated with a thin layer of aluminum oxide at the end of the process as the air is let into the chamber. Unfortunately, this doesn't happen when you polish the surface with some chemical as the chemical will want to make other compounds.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Better read up, the overcoating isn't aluminum oxide, not sure what I had mine coated with, but I sure as hell didn't pay for aluminum oxide. Or, if I did, I sure as hell got ripped. Aluminum oxide forms almost instantly when the new mirror hits the air, and the overcoating is there to prevent it, as well as scratches and other forms of coating abuse. Barrium oxide comes to mind, but I'm not sure, it's been a while.

Silicon monoxide, SiO, is the usual overcoat.

Gary