Well, while I realize double exposure would work, as would many other things, my point with posting is to find out if my thoughts on a white background on slide film producing a clear area on the film, once processed. Obviously, with negative film anything white would turn out as a honkin black area on the processed film. Plus, I'm trying to figure out a way to, without double exposures, create the needed effect. Working out double exposures can be tough enough for someone with experience, but just assuming we're dealing with someone who has little to work with outside of a camera and some film, how it could be done easily.
Obviously taking an outdoor shot then moving to an indoor shot for a double exposure would require some thought on the part of whoever does the faking. But, like I said my needed input was mainly in the properties of a slide film when dealing with white colors. As best I can tell anything I've got on slide that's white in life is a clear, or almost clear area on the slide.