Gelling Windows for DFN

David Grantham · July 13, 2011

So I'm thinking 1 layer of 13% plexi (-3 stops) over 2 layers of ND9 (2 x -3 stops) for DFD and another layer of ND9 (-3 stops) for DFN...

...But never having used window gels I don't know that they won't stick together or wrinkle. If I use a firm stop (I think I can) to keep the plexi firm against the glass I mght be able to solve the second problem.

The latest is that - according to my local gel supplier - this should work (and allow me to reuse the gels if I also store them between layers of plexi.) So I've ordered a piece of plexi to test and will report, but if anyone's tried this - and/or has tips - please let me know.

David Grantham · July 16, 2011

Reusable gel off a roll? Not a chance. We ended up adding soft nd on top of hard gels the rigging crew installed, and some of it looked pretty crinkly. If we had to do again, I think the order would be for two layers of hard gels. I mentioned the camera scenic's dirtying up the window, that's what sold it for me.

I've tried something different and it appears to work. Working on the inside of the windows, I layered soft gels (dry) between 1/8" tinted plexiglass and the window pane. A set of new and temporary window stops (3/16' x 3/16") hold the plexi in place, affixed with outdoor carpet tape for a strong but temporary bond (if not left on more than about a day. It will however remove any already weakened spots of existing wood finish and touch-up will be required.) The plexi has to be cut a bit smaller to allow it to expand and not want to bow out with the heat of the light it absorbs. Probably the gels too. The stops conceal the resulting light gap. And everything stays perfectly flat. No wrinkles at all. It helps to be able to snap out this entire window sash and assemble all this with the pane lying flat.

I've added up to 3 layers of soft gel in there, and the gels come out just as perfectly flat as when I put them in. Stored between sheets of stacked plexi of this identical size (I'l be making 16) in a box of the same size should keep everything in great shape (This is a very dry climate so that should help.) In this case I'm going to be shooting many projects over a year in the space, so it's worth it (not very $, actually) to mill and stain these stops and cut all the plexi (that's the $$ part, even with standard industrial tinted plexi from one batch - can't afford that many hard gels.) Many other materials would work for glass stops other than wood. The whole assembly actually appears to stay in place just with friction but I'm not trusting that.

The attached images show only one layer behind the tinted plexi to balance when so much light is still coming in (an uncorrected pane is visible above the corrected one.) When the space is darkened with all the windows gelled and the space lit (1k in this 12x12 room) I have to add another layer as I light and open up. And yet another soft gel for DFN (maybe a blue one.)