Is aluminum shinier than steel when polished?

I'm trying to make a parabolic reflector out of a used solid-metal (not mesh) satellite dish and I have the option of an aluminum or steel dish.
Would aluminum or steel be easier to polish to a reflective surface?
Thanks
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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
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I want to reflect light.
A.Gent wrote:

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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
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Basically I wanted to know if I could make this:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category2848&item090210674
look like this:
http://www.fleetie.demon.co.uk/curt_searchlight.html
The one in the second link is aluminum, but I can't find any aluminum dishes.
A.Gent wrote:

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Coooooool. You get many B-17s flying over your place?
Have fun with it.
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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
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com =================================================
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one (B-17) went right by my home last week.
At first I thought we were under attack by the Confederate Air Force. I guess they were on a recon flight.
Fantastic, beautiful sound. Paul in AJ AZ
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Lucky man. Best I get here is the occasional DC-3. (Sorry... "Dakota")
Better than nothing, 'though.
-- Jeff Sydney, Australia
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How about a fiberglass dish with silver mylar bonded to the surface?
A.Gent says...

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wrote:

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...
http://www.geocities.com/bobz299/searchlight3.htm
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.
--<< Bruce >>--
--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
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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
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com =================================================
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http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category2848&item090210674
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.
--

SVL




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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
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Michael Shaffer wrote:

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....
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On Sat, 10 Apr 2004 20:54:52 -0400, Michael Shaffer wrote:

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.
--
Skuke
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skuke wrote:

Wonder how large a chrome item can be ? That might be best.
Martin
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being as the steel dish shown in the e-bay URL is made up of pie shaped pieces bolted together, if it were disassembled I think any chrome shop capable of doing car bumpers should be able to chrome plate it with no problem. Bear
On Sun, 11 Apr 2004 04:54:32 GMT, "Martin H. Eastburn"

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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
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On Sun, 11 Apr 2004 10:46:40 +0100, "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.
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