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I found this earlier today about a guy who made his own, painted screen, and he applied a layer of glass beads used in sand-blasting.

http://makeprojects.com/Project/Glass-Bead-Projection-Screen/685/1
The main problem with that tutorial is the size of glass beads used. They are listed as being 80 grit which roughly equates to 195 micron. This is WAY too large a bead to use for a projection screen for most personal HT's. In comparison, the Da-Lite High Power glass beaded screen used to use 9 micron beads (the newer version uses a bit larger). I have some 50 micron beads I got at a craft store and these are also too large to make a good screen.

To give you an idea of what a difference the size of the glass bead used makes here is a microscope photo I took of my 50 micron beads. Now take notice of the much smaller glass beads underneath the larger ones. These are from an extremely expensive reflective paint that came from overseas.

 

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Discussion Starter #3 (Edited)
Is the overseas paint from Australia?

Any ways, this has me interested and I have been searching for very small glass beads. I wonder where they got such small glass beads?
 

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Is the overseas paint from Australia? I wonder if its the DIYTheater paint, like what I sent you
I believe it was from the U.K..

One of the big problems with making retroreflective screens is getting an even application of the beads (even if you can find the right size). The beads pretty much have to be applied after the final layer of paint is sprayed/rolled, but it isn't as simple a process as the page you linked to makes it sound. If the paint is too wet the beads will sink too far into the paint, if it's too dry they won't sink in deep enough and will be easy to brush off the screen as well as not performing as they should.

As for paint that has beads already in it, there is a real problem getting even coverage when rolling or spraying. Not enough paint and the results are "splotches" of varying reflectance; and the same problem occurs if too much paint is applied!

The best retroreflective screen results when a single layer of beads are put down so that 1/2 of their diameter is below the surface of the paint. In the case of commercial screens the beads are applied by electrostatic attraction, something the DIY'er can't do.

Any ways, this has me interested and I have been searching for very small glass beads. I wonder where they got such small glass beads?
We found several sources for beads of the proper diameter, but they were fantastically expensive! They were sold by the gram! Other potential sources were only interested in selling in 25 kilo amounts!

If you want to do your own research into this look for glass beads (preferably with a refractive index of close to 2.0) in the 10 micron to 25 micron size range.
 

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Discussion Starter #5
Wow... they got the bead application down to a serious science with using electrostatic forces to pull them down. Almost sounds like a powder coating process but more refined.
 

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Discussion Starter #6 (Edited)
1) OK... I found a place that sell them, they are called "glass microspheres" and they sell a kilo for $79 and 2 or more kilo for $64/kg. This is for a D90 size of 8um with a mean diameter of 3.5-5.5um, index of refraction is ~1.51

Assuming these can work, this actually sounds feasible to me. However, I have no idea how many kilos I would have to buy for a 4'x8' screen. I'll have to look into how they are mixed, by weight, or by volume.

EDIT: OH SHAZZAM! You can get optional coatings: Fluorochemical and Silane. Fluorochemical aides in bringing the spheres to the surface and Silane improves their dispersion.

Glass microsphere data sheet

2) I found a company that makes a two-part reflective paint that uses glass beads. The size they use is huge, like the link I posted here first, but they state the the two-part epoxy is designed so that the beads "float" to the surface. Hrmmm... Maybe, their paint can be used with the beads that I found above?
 

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That is a great find eb! :clap: I'll check that first site more thoroughly when I have some time. The beads you listed could well work, but they aren't all that round (85%) and the mean size is between 3.5 and 5.5 micron. This is getting a bit small. Something I found out several years ago when I was looking into retroreflectivity (I believe it was in a paper by NASA) is that when glass beads get very small they become optically dispersive and actually deaden reflection. Unfortunately they didn't say at what size this happens.

It looks like you are on the right track! :T
 

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There is artist supply paints that have glass beads in them. Expensive.. and you don't wanna screw up.

electricly charging the paint can be as easy as applying heat.

I used an aluminum screen once and had various metals in the mix geometrically cut and used a powder coater to apply the coating and we heated the aluminum to provide the directionality desired for the screen.

It was way more expensive than just going out and buying a screen and the application process was pretty fatiguing.
 

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It was way more expensive than just going out and buying a screen and the application process was pretty fatiguing.
That tends to be the problem with these types of things - cost and difficulty. It's just not worth it for the 'Average Joe'.
 

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If you take one of the screens say the DaLite Matte White and just buy the material which already has a black backer on it and have it shipped for the screen size you want to your door. You have to equate buying all the materials and the logistical costs to bring everything together and even if you do not put the value of your time into the equation I don't ever get to satisfy the most basic element that motivates people which is saving money.

Far too often the notion of what it cost in DIY the real costs get lost. If you look at the ProjectorCentral article where he states he wanted to get a budget under x dollars. If you added up the ALL of his costs in Evans little adventure is it really going to add up to less then 100.00.

The material I use are more expensive than house paint so the equation is always that it become more expensive.

If the motivation is cost.. Best to just be honest with ALL the costs. I wouldnt go out and buy a respirator and a spray gun if you are only going to do this once. I would go to a body shop and bring the materials to the body shop to get it painted.
 

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Hi Guys,

I'm a long time lurker, first time poster from The Netherlands and let me say just what a great work everyone here does. The amount of information is just astounding.

These glass beads are intriguing, especially now that they seem to be available in the right sizes for a reasonable price. I've been looking into building my own polarization preserving screen for passive 3D viewing, but so far I've not started yet because of the constantly reported problems with hot-spotting. I'm wondering if these beads could be used on top of an aluminum based paint to create a retro-reflective polarization retaining screen. Basically that should eliminate the perceived hot-spot in the center of the screen by turning the entire screen into one giant hot-spot. What do you guys think, would this have any chance of working?
 

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Hi Guys,

I'm a long time lurker, first time poster from The Netherlands and let me say just what a great work everyone here does. The amount of information is just astounding.

These glass beads are intriguing, especially now that they seem to be available in the right sizes for a reasonable price. I've been looking into building my own polarization preserving screen for passive 3D viewing, but so far I've not started yet because of the constantly reported problems with hot-spotting. I'm wondering if these beads could be used on top of an aluminum based paint to create a retro-reflective polarization retaining screen. Basically that should eliminate the perceived hot-spot in the center of the screen by turning the entire screen into one giant hot-spot. What do you guys think, would this have any chance of working?
Hi, welcome to HTS! :wave:

I don't know for sure, but I think all the refraction of the light rays as they pass through the glass beads twice (once going in, reflecting off the backing and then coming back out) would depolarize the light rays.

 

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Hi, welcome to HTS! :wave:

I don't know for sure, but I think all the refraction of the light rays as they pass through the glass beads twice (once going in, reflecting off the backing and then coming back out) would depolarize the light rays.

Thanks, good to be here :)

Yeah i am/was afraid of that. I guess I can do some testing to see if going through a lens depolarizes the light, but it makes sense. Too bad :(
 

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My diy glass bead experiment. Seems to work if done right and is fairly cheap.

While it looks like I just got a shipment in from Columbia, it is in fact powder sized glass beads.
 

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Wow pretty interesting results. It's a bit hard to judge from these pictures, but it certainly seems to reject ambient light very well. Does it increase the gain as well?

What method did you use? Did you pray them on or just spread them over wet paint and shook of the excess?

Can't wait to see some more results!
 

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I did neither. I couldn't get good results by dropping it on top of the paint. Mixing the glass with the paint doesn't work at all. They loose all reflective properties if they are completely covered in paint so you need at least some of the glass exposed.

I found that sprinkling it on wet paint meant that it either sunk in too far or not enough of it stuck so I ended up with a shimmer on top of whatever screen surface was underneath.

In the pic, I had an undercoat which is aluminum ink (not paint) mixed with a little black paint which gave me a slightly tinted metallic surface. With a brush, I then painted a really thin layer of carbon fiber resin. This is basically a transparent epoxy. With a brush, I was able to coat the surface with a layer that was thin enough to leave most of the glass exposed. This kind of epoxy is sticky enough to glue an elephant to the ceiling. No joke, I really suggest gloves for this unless you are ok with a sand paper like consistency on your hands which may be uncomfortable in certain situations!

Before the exposure dried, I just tipped the bag of glass over the surface and tilted it until it covered every bit of exposed epoxy. It takes less then you might think. Only a thin layer of glass will stick and the rest will fall to the next but. When it is all covered, the remainder will just fall off when tilted and can be reused. Within 45 minutes, it will be rock solid. The next day, any excess can be brushed off and it's ready for testing.

On the increase in gain, it kinda depends where you are sitting. You need to be opposite the screen and ideally, on the same level at the projector. I was using it more as a translucent light diffusing layer to give me a watchable screen on a surface that would normally have been too dark. With the lights on, it gave me a really clear high contrast screen with amazing depth. With the lights off, it is noticeably a little brighter than the white screen. I saw a larger increase in gain when I applied the glass to a plan white surface which I also found to be a waste of time. In bright conditions, it isn't gain that suffered with white screens, it's contrast and even with greater brightness, blacks still look washed out.

One thing I would say about glass powder sized beads is that you do end up with a really smooth, but well diffused surface. Nothing like the visible sand like texture I have seen with larger beads.

I am always skeptical about the gain numbers claimed by commercial screen makers. They often claim a gain of 2.5 for their glass bead screens but the ones I have seen are all white and still look terrible with the lights on when using a dim home theater projector. Has anyone ever seen a white glass bead screen that looked good in a well lot room?

Either way, this method is cheap enough to warrant a few experiments if you are like me and enjoy that kind of thing.
 

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I know the pics aren't great. I had to reduce the quality to upload them. You can see the white screen looking washed out as the lights are on and the room is lit from 3 directions. The high contrast glass bead screen looks far more watchable which reflects reality. I can tell you that it takes a lot of light to make this projector look washed out on any surface as it is 5000 lumens which may give you some idea of what the screens are dealing with. I had to shine a sun lamp in the direction of the screens to challenge them.

I have a number of projectors ranging from 700 lumens to 8000 lumens. My quest is more for good blacks with the lights on rather than just more gain to supplement an under powdered projector. What kind of projector do you have?
 

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Very interesting! Can you give us a source and stock number for the beads you used?

As for posting higher resolution photos, you might think about using Photobucket or other free image hosting service and then posting a link or thumbnail that will allow the full res. photo to be seen.
 

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I have a number of projectors ranging from 700 lumens to 8000 lumens. My quest is more for good blacks with the lights on rather than just more gain to supplement an under powdered projector. What kind of projector do you have?
I see. Actually I build DIY projectors for special applications, people that want it hidden in a closet, project through the ceiling, that kind of thing, so I'm not new to experimenting. These kind of projectors used to be very lumen challenged, but these days, with great advances in LED technology, sub-optimal lighting conditions and bad black levels are fast becoming my biggest problems, so this kind of application is extremely interesting for me.

That you are basically bouncing this of a metallic tinted black surface and still end up with a slight gain increase is pretty amazing. That explains the extreme difference in contrast between the beaded screen and the white screen. I could see this working well on quite a few other surfaces depending on conditions. In my home I have a projector projecting through the wall right above my head and a large window in the left wall. The lighting conditions aren't as bad as what you described, but my projector doesn't have your lumen output either. I've been wanting to try a black widow screen for some time, but I was always worried that the gain loss would hurt too much. This seems like a great solution to remedy that :D.

Keep up the great work! :clap:
 
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