Making a safelight for use with red sensitive film (actually any monochromatic film) is easy and by using the right materials you can make a light that is both bright and won’t fog your film.
You might be tempted to use LimeLites and while that will get you by for quite some time, just as nothing beats a spatial filter for cleaning up a reference beam, nothing beats a bright and truly safe light.
You don’t have to break the bank though.
You’ll find lots of references about using "green" filters for a safelight but Colin Kaminski first turned me on to using a Rosco gel.
I didn’t use anything like that for quite some time because the gels seemed expensive and until somewhat recently I was working well with a dim green light, covered with blue tape, aimed at the ceiling.
I recently decided to give a gel a try because I wanted to be able to judge density better than I could with my previous setup. With it, I didn’t have a good way to look through the film and had to use the reflected light from the surface of my processing station. It worked but I was never entirely happy with it.
I went trolling the web and decided that the Rosco #389 Chroma Green filter would fit my needs and ordered it from Acey Decy. Actually I also ordered another sheet of Rosco #19 Fire to play around with using filters when lighting transmission holograms or photographing my deep red reflections. More on that some other time.
The two sheets are shown here. I’ve already used half the green, 1/4 for myself and another quarter for Andres. Each sheet is roughly 20×24".
I cut a 5" strip from one end and then cut that into 4 roughly equal squares. I then took some cardboard and traced out the outer profile of the work light I was going to use, cut the cardboard and then cut a square out of that which was slightly less than 5" on a side.
by layering the filters over the hole the intensity of light of a 25W green party bulb is cut down quite a bit and I don’t see any red when I look at the reflected light from a music CD.
By shining the light on my door I get enough light to see quite well.
Of course, the kicker is if the safelight is truly safe and you can only determine that by testing. So what I did was drop some unexposed film in fresh developer to see what happens when the light’s on. Nothing, even after three minutes. No more reaction than I’d get with the safelight off.