This is from the post at the MSN Groups DIY Projection TV http://groups.msn.com/diyprojectiontv/gene...456510123759727

The Ultimate Projection TV Screen

INTRODUCTION:
This new screen will not be suitable for everyone, because of the cost of materials and availability, and the difficulty of the application of some of the vinyl films.
Also all the materials are only available in a maximum width of 1200mm. so if you want a screen higher than 48", you don't have to read any further.
If you use the materials that I recommend, and the same application techniques, then you will have an excellent quality, very high gain screen, equal or better to most commercial very high gain screens, costing a lot more.
I will give three alternatives of manufacture, ranging from the most expensive (also the easiest) to the cheapest and more complicated method of manufacture.
METHOD 1
MATERIALS:-
1 Sheet 1200 x 2400 x 3mm. Silver Mirror Acrylic ( $150.00 AUD )
1 Sheet 1200 x 2400 x 3mm. Frosted Matt Acrylic ( $83.00 AUD )
Have the supplier of acrylic cut the sheets to the size you require.
Don't try and do this yourself or you will most likely chip or crack the mirror coating.
All you have to do is fix the frosted matt acrylic on top of the mirror acrylic, and you have a top class, high gain screen.
The beauty of this screen is that you can add layers of materials called "Etch and Opal" ( which I'll explain a little later ) on top of the acrylic to reduce reflectivity, should you ever use a higher light output projector like the LCD type.
METHOD 2
MATERIALS:-
1 Sheet 1200 x 2400 x 3mm. Silver Mirror Acrylic ( $150.00 AUD )
1 Piece 1200 wide x 2M.long "Etch" Cast Vinyl film ( $60.00 AUD ) ( available from Signwriters Supply Shops )
This Etch Vinyl film looks just like etched glass, you can't see through it but it allows light to pass.
It is very thin and very sticky, DON"T TRY TO APPLY IT YOURSELF, you will finish up with a bumpy mess with 1000's of air-bubbles. I learnt this the hard way, and I was only using 600mm wide material.
You will need to take the acrylic and the vinyl film to a Graphics Co., and have them apply the vinyl to the acrylic. They use a special laminating machine to do this.
This will give you a screen equal in quality to method 1, but for a bit less cost.
METHOD 3
MATERIALS:-
1 Sheet 1200 x 2400 x 3mm. MDF or Hardboard ( approx. $ 9.00 AUD )
1 Piece 1200 wide x 2M. long "Mirror" Cast Vinyl film ( $68.00 AUD )
1 Piece 1200 wide x 2M. long "Etch" Cast Vinyl film ( $60.00 AUD )
Take these three materials to a Graphics Co. and have them firstly laminate the "Mirror" to the board, and then laminate
the "Etch" on top of it.
This is the method type that I used in my initial tests, and it works very well.
With all three methods, the end result is a screen that looks like a dull flat grey, but when the projected image hits the screen it just comes alive. Brilliant, well balanced colors, excellent blacks and whites, and no hot spotting.
The reason for this is that the mirror behind the top material reflects light back just like a mirror would except it's diffused as it passes through the top layer, and because the top layer is a perfect matt, no reflections.
When I did my initial tests with this screen material, I froze an image that was showing bad hot spotting, and placed the test panel over that area. The hot spotting completely disappeared, and yet the overall brightness was still there, and color balance remained the same.
ADDENDUM:-
If you want to increase the viewing cone of this silver screen, but with the loss of some reflectivity, you can do this by substituting the "Etch" vinyl for a "Milky Opal". This is like a clear material with a slight milky color to it and is available in acrylic. I haven't looked for it in the vinyl, but it should be available.