Actual Mirror as a reflector?

[Anonymous]

Heyas.

I'm going to be taking a whack at a project like this:
http://www.reefcentral.com/forums/showt ... did=437123

But want to make the reflector out of something neato. What about actual mirror? Is that a good material?

 

[Fatal Morgana]

Regular mirror is made of glass, and it is going to be three flat pieces like the link's. Aluminium is easy to bent into any shape you want. Either way, it does not make much of a difference beside the weight and possible cut (ouch!) and broken glass when you drop the whole canopy on the floor.

 

[Anonymous]

Cool thanks for the tips.

 

[Rikko]

Plus a real mirror isn't as efficient as a glossy aluminum or similar. All that reflected light is passing through 2x the thickness of the mirror worth of glass before going out again (light goes through glass, bounces, through glass again). For all the hassle of working with it as well, I wouldn't bother.
Call up a glass/plastic shop and get a quote for the thinnest mirror acrylic you can get. It's great to work with.
You could also try a hydroponics shop for reflective mylar (or something like that) that they sell in sheets. Might be annoying to stick down without wrinkles but it's quite good, too. Just ask your local grow op.

 

[Anonymous]

I realize not a lot of folks live near industrial areas like there are around Michigan here, but you could also check with a local metal fabrication / polishing shop too.

 

[Fatal Morgana]

I would like to make a few comments, if I may.

1, it is true that light will not be as strong due to distintion coefficient of glass, but it is such a close value to aluminum reflector that it is not a strong advantage to use aluminum.

2, the issue with acrylic mirror for canopy is that heat from MH and even PC can cause the mirror to lost shape. I usually don't recommand people to use it in hood unless proper spacing and other pre-caution is done.

3, the same argument for glass mirror can be used on mylar. It is transparent (sic) enough that you can see thru a layer or two if you put it close to your eyes. A few percentage of light is going thru, obvisously.

4, met. fab. shop is useful if they are willing to sell you aluminum scrap. Some may pick a decent piece of nice reflector from their trash bin and give it to you for free. However, don't be disappointed if you have to go thru a few shop to get such freebies.

 

[SaltyMist]

I asked about this on another forum a long time ago, and the responses in a nut shell that I got were simply that glossy white paint reflected back more light than a mirror. I no longer have the message bookmarked (new computer and all), but it did show a chart of what amount of light reflected back from a variety of surfaces, i.e. mirror, glossy white paint, flat white paint, glossy black paint, alluminum, tinfoil, etc. etc. etc.

 

[HClH2OFish]

Hmm..but won't the glossy white absorb some of the light spectra while the mirror would reflect all???

 

[Fatal Morgana]

It is a trickly issue since the mirror can direct the light away from the sensor, giving you a low reading compare to white glossy paint. I did not read the thread, so I don't know if that's the case, but for a poorly built mirror reflector, it can be the case. For example point the mirror so that a large proportion of the light is reflect back to the bulb. Talking about waste of energy

White glossy paint will not have this issue, since the surface acts like billions of randomly oriented mirrors (with a slightly less directional reflectivity), and it will give you reasonable output if you integrate over the surface of the light sphere. The mirror case can give you better output, but you will need to work on it.

There are a few CAD softwares for non-imaging optics, and I feel that is the best way to optimize reflector. But for hobby like this, it is definitely an overkill.

 

[DIY]

IMO i would say mirrors are less efficient in this kind of situation as would be using mirrors in a grow house to help light output/dispursal.. Theres a reason growers do not use mirrors and it is because you will invariably have "hot spots". thats why mylar is the preferred material. the ripples/creases and inconsistencies help to reflect light better.

mirrors are horrible for dispursing/reflecting light evenly.

 

[Fatal Morgana]

Welcome to RDO, DIY!

There are many reasons mirrors are not used in green houses. I agree with you that mirror disperse light not very evenly, but there are some other issues. With shadecloth and other lightweight material, there is no point in using mirror or aluminum and pay several time over in price and weight to get that extra few percentage in light intensity.

If you don't want to spend the time/money in setup mirrors that follow the sun's path aross the sky thru out the day, it is just much easier to get a cheap, light mylar and tape it on without much consideration to optimize the output.

 

[Bishop1]

Remember, not all Al is bendable... because of the crystalline nature of Al, simply buying a "sheet of alumium" and bending it could result in several smaller strips instead of a long reflector! Just an FYI...
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[Anonymous]

Let's start off with the basics. What kind of light are you using?

PC's and normal frosted bulbs are so difused alreaday. So spending time with spectral aluminum, glass, or mylar isn't going to make -that- much of a difference for a 2 or 5 gallon tank.

Use flat white paint. It reflects more than glossy (from the afore mentioned 'lots of little reflectors' property of the gloss)

I think it might be in advanced aquarist.

You could get a small piece of pre-made reflector from any of the sponsors of rdo. I got a 36' single pc reflector for $13 I think, and I cut it down.

B

 

[Anonymous]

Remember, not all Al is bendable... because of the crystalline nature of Al, simply buying a "sheet of alumium" and bending it could result in several smaller strips instead of a long reflector! Just an FYI...

Could be true for some aluminum alloys, but for cheap al. sheet ("pure" aluminum, like the foil used in the kitchen), it is very easy to bend.

 

[Bishop1]

Reef Box:

precisely... some Al alloys are bendable some are not... pure Al sheet is not. Usually bendable aluminum containes magnesium and silicon to keep it from fracturing.

Al foil is bendable either because of it's alloy content or the process in which it's made (rolling).

Either way, when you make a reflector, you want 1/16" or so thick material, just make sure you buy bendable alumium
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[holry7778]

I'd say you are just as good off painting the the hood flat or glossy white (little difference between the two) A metal reflector unless polished to a mirror finish or better doesn't gain you much over the paint.

See this thread
http://reefs.org/phpBB2/viewtopic.php?t=57020&highlight=hood+paint

Plus ease of painting over polishing and cost is low.