There was some discussion of translites earlier in this thread, so along those lines, here’s an incredible album from Doug Drexler’s facebook page describing the earlier process. He also goes into great detail while cleaning up and restoring the TNG master systems display (3x10 feet!) with many photos:
Excerpted from his page, the backlit screen process:
In the early days, every backlit was spray glued to the smoked plex. We used Super 77. It’s like atomic adhesion. They fall in love, and there is no gettin’ 'em apart! Later we learned that you could just masking tape 'em to the plex. Even if they weren’t dead against the glass, it didn’t matter, you couldn’t tell. It also made it easy to swap graphics out on the spur of the moment.
Today I’m replacing the old diffusion paper on the back of the graphic. In the old days we spray glued it over the colored gels. This always proved to be an unwieldy operation with only two hands, and especially with a big graphic like this. We used 77 for this as well, and that stuff is totally unforgiving. If the diffusion folds over on itself, or goes down crooked… you’re screwed. Pulling it back up will ruin all the colored gels that you so lovingly cut and shaped. My blood pressure is going up just talking about it!
Up until about season 4 or 5 on DS9 we made backlits with what today seems like stone knives and bearskins. First you drew it up on paper, or if you were lucky and had a computer, you’d create it as a black and white vector graphic. Now you have to print the graphic out.
We had an 8.5x11 black and white printer in the art department, and that was it. If you had a giant back lit, you would have to print out the large graphic like a mosaic, in 8.5x11 pieces, then trim, and fit, and spray glue them together on a large artboard.
Next you call the off the lot photstat house. they would send a messenger to pick it up, and take it back to the stat house. There they would put it on a large platen with a giant overhead camera, and shoot a large format negative. If all goes well, the stat house sends the messenger back with the giant neg. The fun is just beginning…
Now that you have the film neg of the graphic, you have add all of the colors by hand. Denise and I would go over to the grip and lighting department on the lot, and pick up rolls of gels made by Rosco. The gels are flexible rolls of material like acetate. They are used on stage by the grips to put over lights in order to tint them… if a scene is cuddly and happy, you might put amber gels on a light, and so on. Get it?
Mike kept all of the displays to a very finite color palette. The was very wise, and we were able to give every alien races graphic an identity thru color scheme. If you use every color in the rainbow, you end up with a muddy mess, especially when these things end up being out of focus blobs of light behind the actors.
So you hand cut these colored gels, and glue 'em where you want color. We used a spray glue made by 3M called Spray Mount. This is a low tack spray that allows you to reposition the gels. Once all of that is done, the scary part is dead ahead. Gluing down the diffusion!
So saddle-up, and take a little trip back thru time with 'ol Doug. This is how we used to do it in the before times. Now, you simply press a button, and a giant printer in the sign shop spits it out whole… color… diffusion… the whole magilla, in one shot! Ain’t technology wonderful?