# Mylar reflectors



## Henry Hatch (Dec 12, 2006)

I have a 20 gallon tank with a cheapo light fixture that has a white plastic reflector. I'm planning to line the fixture with 2mm thick mylar. What is the best way to attach the mylar ? Should I use tape or glue ? I'm concerned about melting adhesive or having it catch fire. If this works I may try it on a fixture with an aluminum reflector, but I don't want the reflector to be ruined if I decide to take out the mylar. 

Henry


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## cah925 (Jun 23, 2007)

I used a spray enamel for use on metal or wood that I bought from Home Depot. Spray on a lot the first time so you don't have to fix it later. Lay the mylar down and use a credit card or sqeegee to push the air out. I let mine dry overnight, but the instructions say 10-15 minutes. After that, just cut off the excess and install the light. I used this on 2 shop lights about 3 months ago and so far it has worked great.


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## SPC (Dec 6, 2007)

I used Mylar with a VHO hood 7 or 8 years ago. If I remember corectly I used a double sided high temperature tape that I purchased from a heat and air supplier. I do remember, however, that the mylar began to fall apart at about the 2 year mark.

Steve


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## dansbdk (Mar 16, 2008)

You can also try a spray adhesive available anywhere.
And the Mylar can be removed, and repositioned before the adhesive completely dries if you make a mistake! it's non-flamable after it drys, and the adhesive can be removed with GooGone, if you decide you don't like the Mylar!
Good luck!
Dan in Va


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## pinantanjohn (Apr 20, 2008)

Actually it sounds counterintuitive and I didn't believe it when I heard it, but flat white paint is better for reflectors than mylar, especially close to the bulb. I used to grow plants hydroponically indoors under sodium lights and I tried everything including mylar. I got the best growth and most even lighting with flat white paint. Mylar can create "hot spots" in the growing area and can focus a lot of energy right back into the lamp with a reflector that wraps around the bulb. Not really dangerous with flouros but can kill HID's really fast.
To get the most "bang for the buck", try white paint.

Peace...
John


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## hoppycalif (Apr 7, 2005)

Whether white paint is a better reflector or not depends on what you are trying to do with the reflector. White paint gives diffuse reflection - it reflects each "ray" of light in all directions, not just one. You can't aim a white painted reflector to direct the light into the tank. Much of the light will be reflected sideways, to strike the reflector in another location, where much will again be reflected sideways, etc. If the reflector is just the flat surface behind the light bulbs, white paint is probably better than mylar. But, if the reflector is a curved reflector behind each bulb, intended to redirect that light striking it towards the water, mylar is much better. Note that the expensive T5 fixtures all use polished aluminum reflectors, not white paint.


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## dgphelps (Jan 1, 2008)

I've seen a few DIY projects using mirrors behind the bulbs... Any thoughts on that as opposed to mylar, aluminum or white paint?


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## hoppycalif (Apr 7, 2005)

Since I posted my comment above I have done some testing and, to my surprise, good bright white paint is a very good reflector. Plain aluminum foil is also a good reflector. Mylar isn't as good as either of those. Glass mirrors, with the aluminizing on the back surface of the glass would be worse than all of the three above. Glass mirrors are very good for reflecting a true image of what you want to see, but not good at all at reflecting almost all of the incident light on the mirror. Front surface mirrors, like are used in astronomy telescopes, would be excellent reflectors, but protecting the very thin coating of aluminum without reducing the amount of light reflected would be a problem.

Any new light fixture I make I will probably use the brightest, most glaring white paint I can get as the reflective surface.


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## xdoomsongx (Jun 27, 2008)

I use plain aluminum foil on the fixtures that I would like to get a little extra from. I stick it on with double sided tape. I have one tank that I have had this on for the past two years with no problems. I am not growing plants in said tank mind you, just wanted it to be a bit brighter. I have been very pleased with the results. The last DIY fixture I made I used high gloss white paint, and it is almost painful to look in the fixture with the light on, I think it works very well for reflection, but as of now, I have not gotten a chance to plant the tank. Look forward to seeing how it does.


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## hoppycalif (Apr 7, 2005)

Here is some interesting information I found by an hour of googling:
www.usu.edu/cpl/PDF/Barium_Sulfate.pdf,  which discusses making a high reflectivity white paint by mixing barium sulfate into latex paint. A cheap source of barium sulfate powder is http://www.sciencestuff.com/prod/Chem-Rgnts/C1296. I have bookmarked this site in case I decide to make a new light fixture sometime.


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## xdoomsongx (Jun 27, 2008)

> Here is some interesting information I found by an hour of googling:
> www.usu.edu/cpl/PDF/Barium_Sulfate.pdf, which discusses making a high reflectivity white paint by mixing barium sulfate into latex paint. A cheap source of barium sulfate powder is http://www.sciencestuff.com/prod/Chem-Rgnts/C1296. I have bookmarked this site in case I decide to make a new light fixture sometime.


Great info, thanks for sharing! Is there such thing as Super White?


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## hoppycalif (Apr 7, 2005)

xdoomsongx said:


> .....Is there such thing as Super White?


I looked at several paint companies websites and it appears that almost all, if not all white paint now is tinted to reduce the glare. I also saw in a few places that commercial white paint only reflects maybe 80% of the incident light vs. the 95% or so that the home made white paint will do. Years ago you could buy very bright pure white paint for houses, but it probably rendered too many people blind from the glare, so they don't do that now. I know "white" houses used to be painful to look at right after the paint job was done. Now, when I last painted my house my wife spent weeks looking at a zillion different "whites", none of which was pure white.

One of the most informative websites was one devoted to discussing the production of pot in house closets, etc. It seems that our whole lighting subject is shared with that group.


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## oregon aqua (Jan 30, 2008)

i seem to remember that home depot has pure white as a base paint. so the colors are easy to make.

its been awhile since i was their.


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## xdoomsongx (Jun 27, 2008)

> Years ago you could buy very bright pure white paint for houses, but it probably rendered too many people blind from the glare, so they don't do that now. It seems that our whole lighting subject is shared with that group.


 :rofl: I also remember when looking at a white house was the equivalent of staring at the sun!


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## Tex Gal (Nov 1, 2007)

I wonder how well the white paint will stick to the plastic of most smaller tank hoods? The Krylon paint is made specifically for plastic, but if I hear you correctly it probably doesn't come in pure white. Do you need to apply a chemical sander to the plastic first?


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## hoppycalif (Apr 7, 2005)

You should be able to use a Krylon primer as a first coat, then switch to acrylic paint for the bright white coat. It looks to me like the reflectivity difference between high reflectance white and regular white paint is big enough to go to some inconvenience to use it. Like a 20% gain in reflectance. That could be enough to make a difference in an aquarium.


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## Tex Gal (Nov 1, 2007)

Thanks Hoppy. I appreciate your wisdom.


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## zer0zax (Mar 25, 2007)

Good stuff Hoppy. Do you think pure white paint will reflect more than aluminum?


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## hoppycalif (Apr 7, 2005)

zer0zax said:


> Good stuff Hoppy. Do you think pure white paint will reflect more than aluminum?


I find it very hard to understand how white paint can reflect more than shiny aluminum, but from everything I read, and my own measurements, it seems it can. I'm planning to try some more experimenting with a simple fixture and a PAR meter to see if I can convince myself one way or another.


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## wiste (Feb 10, 2006)

> I find it very hard to understand how white paint can reflect more than shiny aluminum


If you are using Mylar with a reflectivity of say 98%, then white paint does not reflect significantly more light. If it does then the reflectivity rating is incorrect.
It does make since that white paint reflects light in a diffuse pattern that is more forgiving of a poor reflector design.
For example, the Mylar reflector may reflect the light back into the light bulb or give a poor light distribution.
Saying white paint reflects more just does not seem logical.


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## zer0zax (Mar 25, 2007)

Hoppy posted some interesting numbers using a par meter, he tested different materials on the same reflector so shape was consistent. Unfortunately I don't know how to post a link to that thread though..

My bad for not being specific Hoppy, I meant to ask if you think that ultra white paint is better than aluminum foil. If you get to borrow that par meter again my head will hurt all over again!


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## oregon aqua (Jan 30, 2008)

http://www.aquaticplantcentral.com/...ty-variations-some-thoughts-7.html#post387592



hoppycalif said:


> Today I measured the light intensity from my 55 watt AHS Bright light kits in my 45 gallon tank light fixture, for different reflector materials, as suggested by Orion2001. To make this easier, I did the measurements with only one bulb of the two installed. First I checked the reflector with no modifications, using the same technique as I used for this fixture before. Next, I covered the AHS reflector with aluminum foil, trying to minimize the wrinkles in it. And, finally, I covered the reflector with white paper, spray painted with glossy white paint. All of the PAR measurements were taken at the fixture centerline, so the light was affected by the reflector, since that bulb was off center above the sensor.
> 
> I plotted all of the data, plus the data taken with both bulbs installed, on one graph:
> 
> ...


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## wiste (Feb 10, 2006)

> Hoppy posted some interesting numbers using a par meter, he tested different materials on the same reflector so shape was consistent.


The shape being consistent does not imply that the shape of the reflector does not favor a reflective surface that spreads the light vice a reflector that reflects more light but the reflective pattern is more directed. E.g. the light might be directed directly back into the light bulb.


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## zer0zax (Mar 25, 2007)

Thanks for putting up the link Oregon aqua!

Wiste, my knowledge of lighting and aquariums in general is pretty limited, but IMHO the AHSupply reflector that Hoppy used in his demonstration was as good as it gets, the results really are jaw dropping. I don't have these reflectors myself but it seems that everyone who has ever owned them thinks they are worth their salt. These reflectors are very good at directing light into the tank and minimizing restrike, or light being thrown back into the bulb. 

The main downfall is that the PC bulbs are in a dual configuration and mounted very close to each other, so there is a lot of effective light lost before the reflector even gets a chance to reflect.... sorry, long winded! My point is that the AH reflector used is probably the most efficient one out there for the PC bulbs, its not just a flat hood with lights mounted underneath scattering light everywhere! I will retire for 5 minutes and let the experts edumacate me sumore:clock:!

(By doing some calculations at home and a bit of black magic with my own numbers based on nothing substantial whatsoever I have concluded that a PC bulb could put out 15% more light per tube (or half) if spaced out and placed under an individual reflector (such as T5 lighting), for a total of 30%! (2x [email protected]%))


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## wiste (Feb 10, 2006)

> the AHSupply reflector that Hoppy used in his demonstration was as good as it gets


Unless I missed something, the readings for the AHSupply reflector modified with different reflective surfaces do not include readings for mylar.


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## hoppycalif (Apr 7, 2005)

wiste said:


> Unless I missed something, the readings for the AHSupply reflector modified with different reflective surfaces do not include readings for mylar.


You aren't missing anything. There was no easy way to try the mylar on the AHS reflector, and I was much more interested in aluminum foil and white paint when I did that.


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## zer0zax (Mar 25, 2007)

EASY question: aluminum foil, or white paint?


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## grim (Mar 13, 2008)

Sherwin Williams makes a paint line called super paint since the tints are made to take away the reflectivity of paint if you at 1/16 ounce to 2/16 ounce of white to the paint it will bring the reflectivity back up this can be done to almost all paints the reason i say super paint over there new line duration is because of the price duration will lay flatter with less brush strokes but if you mix 8 ounces of water into one gallon of paint you'll get close to the same affect as duration you could try one of those black sponges on a stick for no brush strokes but i don't use them so i don't know how they work


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## oregon aqua (Jan 30, 2008)

Hoppy did anything ever come of that Barium Sulfate? Didn't you order some and where going to test it?

I love bringing back post!


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## zer0zax (Mar 25, 2007)

Yes! Show us the good stuff and bust some more myths!


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## hoppycalif (Apr 7, 2005)

oregon aqua said:


> Hoppy did anything ever come of that Barium Sulfate? Didn't you order some and where going to test it?
> 
> I love bringing back post!


The barium sulfate experiment died on the vine! I ordered some from ebay, but PayPal refused to allow me to pay for it with their service, even though the seller asked for PayPal payment. When I tried to email the seller for clarification he/she wouldn't answer emails. I cancelled the purchase as a result. Then I took a week off to go to Alaska and forgot all about it.

It is still a good experiment to try, and maybe I will some time, but now I am concentrating on a design for a light fixture mounting device, possibly to be given to someone to sell from their store. (hint!)


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## mulita (Jul 31, 2007)

I just build a reflector for my lastest project, this is for CFL bulbs and I built it out from aluminum plate 18ga Pre Painted with White Powder Paint coated, this gives exactly the same finish as a commercial reflector. I also make it similar to AH reflector to try to make it more eficient. Here are some pictures. (I took the pictures yesterday night)

Here is the reflector shape









Here is the white surface on it.









Another Shot.









This is where it will go.









I am planning to add 2 CFL more to what I have with a similar but smaller reflector to them but I am figuring out how to make them removal from the area for maintenance.


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## hoppycalif (Apr 7, 2005)

Wow! That looks like a professionally made reflector. I like the deep dish design too - the deeper you put the bulbs down into a reflector, the less spillover light you get.


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## mulita (Jul 31, 2007)

hoppycalif said:


> Wow! That looks like a professionally made reflector. I like the deep dish design too - the deeper you put the bulbs down into a reflector, the less spillover light you get.


Thanks Hoppy, I followed your advice on it, How do you look at the white paint that I am using for?, one thing you can notice is the very smooth painted surface which makes it more efficient as reflector.

I plan and scale this reflector to have the bulb more-less down centered within it also having the reflection angles properly distributed around the lamp. I really like how it ended, so I am going to build its partner for the second lamp and two more smaller version to fit another two lamps.

I am thinking the way to attach it for the bulb as I want to have easy access to it for lamp change, these two will probably will be really easy even having the reflector fixed to the cabinetm but the additional two, is going to be another story.


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## hoppycalif (Apr 7, 2005)

I don't know how to judge the reflectivity of a white paint. All I really have to go on is my memories of white house paint from many years ago, when white was just white. Back then a newly painted white house was hated by neighbors because it blinded them to look at it. And, that was flat, not glossy, paint. Today, white paint is very rarely white - it has tiny amounts of other colors in it, which greatly reduce the reflectivity. I suspect that flat paint is better than glossy, but I don't really know for sure.


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## mulita (Jul 31, 2007)

I remember that kind of white, my parents house used to be like that, painfull to look at during a sunny summer day. My best reference now was to compare it with a commercial reflector, and it look exactly the same. There is no sunny days here now, so I cant take it out to check 

Without a meter is going to be hard to judge, I guess the plants behaivor will be the best judge for it.


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## zer0zax (Mar 25, 2007)

That looks awesome Mulita! What did you use to bend the reflector? Your process looks flawless!


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## mulita (Jul 31, 2007)

Thanks Zer0zax, I used a Hydraulic Press Brake (Industrial), it is truly flawless as this aluminum sheet is prepainted and the paint can hold the bend without showing any damage.

I have already installed 2 of these reflectors and even when appearently light look about the same, plants have started to show a difference.


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## zer0zax (Mar 25, 2007)

I'm starting to get a bit jealous:roll:! Guess I will have to take a trip to Mexico! Thanks again for sharing:yo:.


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## mulita (Jul 31, 2007)

You are very welcome to visit! but I can also send you a pair of these if you are pacient enough.

Here is a picture of the set installed, I glue them using No more nail glue avoiding bolts to have pure white surface on it.










I also built a shorter version of the reflector to add a second set (about 5.5"), but the space I have is really limited so I am still figuring out as I may affect a cooling modification I just made for the aquarium.


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## zer0zax (Mar 25, 2007)

Would a hardware store or paint supply store have pure white paint? Most places will custom blend/match paint for you, hopefully they would have some kinds of plain base colors without any tints. I keep thinking about tinfoil but white paint would be easier, and when Hoppy compared the two he only used painted paper....no wonder white paint looks so promising!

I tried googling?! reflective materials and kept ending up on weedgrower sites (terrestrial kind) to, and most of those guys prefer white over tinfoil. I guess I will only use tinfoil on my head, not behind my bulbs.


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## mulita (Jul 31, 2007)

If I wasn't doing it with a prepainted sheet, I would use an Aerosol white gloss color to paint it (3 layers minimum). I used a similar kind of paint for the inside top of my Wall aquarium to improve reflection and it works really good.


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## Javaman (Nov 19, 2007)

thank you for info


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