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Thread: Heat Reflective Ob Coating

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    Exclamation Heat Reflective Ob Coating



    Just came across a post over on http://tech.groups.yahoo.com/group/O.../message/13319 (Observatories), which has me vibrating (at my age, it doesn't take much ) as I'm about to paint my dome. There is a aluminum finish coating called LO/MIT which has been used on the Aura Gemeni 8 meter ob on Mauna Kea, the GGTC Project in the Canaries, among others, so its well tested.

    Its affordable at $65 a gallon, is best sprayed on as it only needs a 2 mil thickness, but can be rolled or brushed. For more: Welcome to SOLEC-Solar Energy Corp..

    Last edited by BobDob; 09-03-2009 at 02:49 PM.
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    Bob I love solar energy but i didnt know about this outdoor paint, i also have heard of insulating indoors paint that really makes a difference not sure the cost however or name-brand

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    That paint sure beats the traditional titanium oxide white that was used on the Mount Wilson domes...
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    How so, Matthew?

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    Better heat rejection. Keeps the dome cooler to match nighttime temperatures. I do know that in the 1930s the 100 inch Hooker dome was painted silver. At some point in time they painted it white.
    Matthew Ota
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    Souns like cool paint Bob. I bet we can see it on google earth.
    name: Derek

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    How about the silver reflective brush on coating for mobile home roofs? It's available at Sears and hardware stores.
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    Dunno, T, I guess I'm real impressed that the international ob's are not using mobile home roof coating but this other stuff. I believe it works on the principle with Reflexic bubble foil insulation. The phenomonon is that aluminum does not transmit heat, or sumptin' like that .

    IOW, its not the color but the material that makes the difference. Here we're talking about a two mil coating, not a goop of colored stuff intended to seal and reflect sunlight. I'm guessing the former is much more effective as a thermal barrier.
    Last edited by BobDob; 09-04-2009 at 02:15 PM.
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    Default White is better at reflecting heat

    Quote Originally Posted by BobDob View Post
    Just came across a post over on Yahoo! Groups (Observatories), which has me vibrating (at my age, it doesn't take much ) as I'm about to paint my dome. There is a aluminum finish coating called LO/MIT which has been used on the Aura Gemeni 8 meter ob on Mauna Kea, the GGTC Project in the Canaries, among others, so its well tested.

    Its affordable at $65 a gallon, is best sprayed on as it only needs a 2 mil thickness, but can be rolled or brushed. For more: Welcome to SOLEC-Solar Energy Corp..
    Hi Bob!

    After many years of working with advanced composites the community agrees that white is the only color to use when attempting to tame heat.

    Anything else absorbs some heat, especially black which is the worst offender of the lot.

    The observatory we have in Voorhees State Park in New Jersey benefited from this recently when it came time to paint the dome for our 26" Cass.

    The mirror is 6" thick and after a day of soaking in the observatory room at 115 degrees or more, it would not reach thermal equilibrium until 2 or 3 AM!

    When it came time to paint the dome, they like you, felt that aluminum was best. I cautioned them that the sun sees aluminum not as a reflective medium but as a grey. To turn doubters into believers, I had them ride around parking lots and place their hands on the roofs of parked cars on a sunny day and compare the amount of heat.

    It did not take long to get agreement: white is best. I learned all this from Burt Rutan 35 years ago and it's still true today.

    Voorhees volunteers did as was indicated and the reports are that while there is still some heat build up in the dome on bright sunny days, the temps have dropped significantly.

    I invite you to try it. White gloss enamel is about one fourth the price of that fancy paint and does a better job.

    Clear Skies!

    Art
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    Smile

    Thanks, Art, for your insight. Bear in mind, we are not talking a coating material or color, but a heat barrier with this stuff. I haven't tried this material, but I have used the Reflexic material for insulation, and I really like it as there's no fiberglass fibers floating around in the enviornment. Foam insulation is better than glass, IMO, but only after the outgassing is complete.

    As I see it, due to the thermal non-conductivity of aluminum, coupled with the ceramic microballs, this stuff could be excellent! I just haven't had an opportunity to test it out

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