I posted here yesterday about the Destination Imagination creative problem solving program. I was the Team Manager for a DI team for 10 years, and the kids made some wonderful creations. I thought I'd share the details of one with all the Makers here.
A few years ago, my teams challenge included a requirement to depict some aspects of the culture of three different countries. They would be performing a skit and demonstrating several technical devices as the main part of the challenge. The team decided to create changing background scenery with a synchronized musical soundtrack using a laptop computer, a video projector, and a speaker system. The cost limit for the entire presentation (devices, props, scenery, costumes, etc.) was a total of $150, but audio/visual equipment and computers are exempt from the limit. The team used Windows Movie Maker to create the video for the backgrounds scenery, but they were missing one important component - a screen to project it on.
Since they would be performing in front of the screen, they knew it needed to be a rear projections screen. After all other devices and props were accounted for, less than $20 remained in the budget for a screen. The requirements then were: - it needed to be about 4' high and 5' across; - it needed to be easily disasembled for transport to tournaments; - it had to be quick to assemble for use (there is an 8 minute time limit for assembly and presentation of the entire solution); - it had to work well in a lighted room, since the team is not allowed to turn off or dim the lights at the presentation site; - and of course, it had to be cheap.
The first version was made with a white bed-sheet suspended from a PVC frame. This screen was disappointing - while the image could be made out, it was dim and blurry in all but the darkest of rooms.
The second version added an enclosure around the projector that extended to the back of the bed-sheet screen to reduce the ambient light hitting the back of the screen. This enclosure hood was made of a PVC frame and black plastic tarpaulin material. The frame could be folded up and rolled within the plastic for transport and quick assembly. The enclosure helped a lot, but the projected image was still too dim to be seen easily unless the room was moderately dark.
Clearly the screen material was inadequate. After a brainstorming session, the team set out to research and experiment. Research on the web discovered a site selling rear projection screen material for custom applications, but in the quantities they needed it was priced at about $25/sq. ft. They took a trip to a fabric store to try to find a material with the right combination of opacity and transparency. A semi sheer silk like material worked better than the bed-sheet, but was still too expensive and left something to be desired. They tried some clear plastic sheeting covered with various paints, shellacs, and other coatings. They tried tracing paper, and other thin paper sheets. Finally, in the Ah-Ha! moment, they found the perfect material right in the kitchen...
Wax Paper!
The first test with a single sheet of wax paper was amazing. It appeared to have the near perfect balance of opacity and transparency. The image was bright and clear even in a well lit room. If anything, it was almost too transparent as the bright bulb of the projector would wash out the image when viewed straight on. To solve this issue, they tried a double layer of wax paper, and it was near perfect. As it turns out, the double layer had other benefits as well.
To make a screen the size they needed, they used several 5 ft long strips laid horizontally, and several 4 ft strips vertically. They weaved the sheets in a basket-weave like pattern, then used a warm iron (with smooth towels on either side of the wax paper) to bond the double layers together. Black duct tape around all four sides was used to prevent rips and to provide a bit of strength for hanging, and also made a good frame for the projected image. The top edge was pop-riveted through the duct tape edging to a PVC pipe, and lengths of wooden dowels were stapled to the bottom edge. The screen could then be rolled up easily for transport. For quick assembly at the competition site, the top PVC pipe was placed on two PVC uprights, and the screen quickly unrolled.
The image quality was astounding, and clearly visible from any angle even in a brightly lit school gymnasium. The bonding of the wax paper sheets with an iron had left a few visible air bubbles (a little more care in the ironing could have eliminated this) but these blemishes all but disappeared when the image was projected. This screen was absolutely perfect for what it was used for - simple, cheap, and easy to make.
If you ever have a need for a quick, easy, cheap and disposable rear projection screen, wax paper is the answer! It will come in great for those impromptu backyard "drive-in" movie shows.
I tried this idea recently, at a formal party. I used it to make rear projected backgrounds for taking photos of friends. We shot over 170 pics with various backgrounds. Worked pretty well. I had a 7x8 foot screen, with PVC pipe as a frame and a bug screen on the front to reduce glare from umbrella lights on the subjects.
I was wondering if anyone has tried using shower curtain liner material. It is purposely designed to diffuse light, yet let light pass through. It is probably less prone to damage (wrinkles, bubbles, tears) than the wax paper.
I forgot to mention, in case you are curious: I did weave the wax paper sections. I also used two layers and iron them together. I could not eliminate all wrinkles and bubbles, because my screen was very large and hard to manage.
By the way, to attach it to the PVC, I used WHITE duct tape.
jasonshinn: Yes, our final version retained the shroud. It may have worked okay without it, but the team had invested enough time into it that that figured they would use it anyway.
3d-animator: our team had a good number of bubbles and wrinkles too, but found that they virtually disappeared once the image was projected. Were the bubbles and wrinkles noticable in your application? 7x8 feet is huge!!
At camp we have 10'x20' white canopy tents, which we use for both front and rear projection. When it's possible to have inclement weather, having all the sound and lighting equipment inside the tent is a bonus. Picture quality is fairly good, but some panels have a seam in them. You can build a more portable version with just a white tarp, which we've hung from trees in the woods.
I have found the answer to the best material to use for a rear projection screen! I found it at J.C.Penny and it cost me only $9.40 after tax.
It is a 100% PEVA "super softy" shower curtain or liner. I choose the frosted finish and in the evening it looks like a flat screen and it eliminated the "hot" spot, from my projector, I had from using white flag nylon.
Best part is the size 72" X 70" I am investigating getting larger sizes.
Okay! I am building a youth center that will have a large gathering of community youth each week as well as be on the road from time to time. What is the best way to transport? Just roll and stuff? This sounds like what we need. Any new thoughts?
Kert Rats: What colour curtain was it? Frosted or White.
I am in England and trying to do the something similar to alan4s but with recording a film with back projections instead. I am having trouble locating materials that match the ones you have where you are. Any other advice?
Alan4s: I am happy to go to a faberic store to purchase material but need to know around about what kind of material I need. What sites did you find?
ironing basket-woven wax paper did NOT work out for me -- the weaves moved around under the sheet i was ironing, slippin and slidin, gettin all out of whack. i found that overlaying strips parallel to each other at the half-sheet mark worked out better and was easier to manage. i did have bubbles, but bubbles in ironed wax paper seem unavoidable.
the shower curtain in question: http://jcp.is/eyWMAA and they just keep getting cheaper on the website for some reason. to get the folds out i threw it in the washing machine and hung it dry.
This is all so fun and interesting, but here's my twist...
I need rear screen projection...where people (using dry erase) can write on the front/audience side.
The shower curtain could work, if stretched. I thought about different flourscent light celing tile covers, and Menards sells a white Acrylic sheet .118.
I found that setting the iron to the lowest level and applying it briefly while smoothing the wax paper out gets rid of bubbles, and fuses the wax paper faster.
35yrshowvet: depending on whether you need to roll up your "canvas" at the end of each night this might not work but... - we used a 4x8 plexiglass sheet, built a 2x4 'picture frame' to house it and keep it steady while people drew on it with 'cafe menu markers' (a nice opaque dry erase marker with a selection of vibrant colours). I imagine that if you stretched the shower curtain behind it you could project images from the back while people drew on it from the front?
For a rigid screen that could be written on with dry erase markers, we used a sheet of plexiglass with a sheet of Vellum taped to the back side (can be found at most art stores). It worked amazingly well, about as good as our $1500 commercial rear projection screen with proprietary surface!