Question: I need to make a window about 5 feet tall by 8 feet wide and was wondering what I should use as the window pane. Just like everyone else, we have a very tight budget.
Answer: Do you really need the window pane? Depending on the distance from the audience, you might get away with just the frame. However, you could use plastic sheeting for the pane if you need some sort of reflective quality. I've used the clear plastic window insulation used for keeping out winter drafts. It works via using double stick tape to attach the plastic to the frame. Then, you use a hair dryer to shrink it tight. You'll find this stuff at almost any hardware store or home center.
Try clear mylar stretched tightly across a frame. It will make the unit very light, look like glass from a distance. As long as it doesn't need to be broken or taped on, it should work fine.
My favorite, low cost, window pane substitute is good old window screening. It comes cheap from any hardware store, does not reflect as much light as plastic sheeting but does play with the light well, staples and cuts easily, and is paintable (a light brush of white paint in some
of the panes gives a nice look). The other nice thing about screening is it also will allow light to pass through.
I always liked black bobinette, no glare or reflection and picks up just enough light to indicate something is there.
Try a plastics shop in your area. They can probably get you a sheet of plastic (acrylic or polycarbonate) in the size you want. I'd go with polycarb over acrylic any day. More rigid and far less brittle. That's probably why we use it for safety glasses, huh? Polycarb will be more
pricey, but will be re-usable far longer than acrylic.
I've had good luck with window screening, as well as black Tulle (the costume shop can probably help you out on this one). It's cheap, too.
I think that one of the most effective windowpane materials is black fiberglass window screen. It comes in a wide variety of widths, and is quite inexpensive. It has a slight sheen that looks like glass onstage without giving you reflections of the hundreds of lights arrayed around it. It is safe to use and it is light. I have had designers insist on glass, plexi, mylar, and more and whenever I have been able to show them both their choice and screening under stage light the screening was the "clear" choice.
One of the finest looking windows you can make on set uses cheesecloth. Apply a single layer of cheesecloth on the backside of the window. Once it's applied, from the front, spray the cheesecloth with black spray paint. Don't worry about getting it perfect. The more you
leave unpainted the more it looks like dirty glass. You will see what I mean when you do it. The nice thing about this method--no reflections and it really looks like glass.