I have been making double exposures and taking part in film swaps for a while now. It's fun to do them, and usually the results are very surprising. Sometimes in a good way, and sometimes a complete failure.... In this blogpost I'll try to explain how to do doubles.
When doing a double exposure you expose the same bit of film twice. When doing a film swap, one person shoots a roll of film, rewinds it, and someone else will shoot it again. Either way, you'll end up with two pictures stacked on top of each other. The success rate depends on a couple of factors.
When doing doubles or a film swap, underexpose both layers. Otherwise you'll end up with an overexposed shot or film. I usually shoot 200 iso film at 400 iso, 100 iso film at 200, etc. On most cameras this is easy to do. Just set the iso manually and you'll be fine. If you do a film swap, inform your swap partner about the underexposure. Not everyone knows this.
For the base layer I try to come up with interesting things. In my opinion there are some subjects that work really great as a base layer: text, neon lights, graffiti, structures and patterns such as bricks, tiles and pebbles and heavy contrasts (black and white objects, silhouettes or trees in the woods). Try to avoid too many light or large white objects in your base layer. Anything white will stay white in the second layer. Unless..... you want to play with this.
If I shoot the second layer, I look for bright coloured objects such as flowers and traffic signs. Portraits also work.
Doubles or film swaps work great in combination with redscale fim. Redscale film is difficult to overexpose, and when doing doubles you don't need to underexpose both layers. It is possible to make your own redscale film. My friend Brendan has written a great tutorial about it. I have done several film swaps where one person shoots the normal side of the film (at box speed), turns the film around to make a redscale out of it, and the next person then shoots the redscale side of it. It is often referred to as a "redscale flip".
Redscale film is also very good for making HQME, or High Quantity Multiple Exposures. That means exposing the frame several times. When I do them, I usually expose a frame 15 to 20 times, moving my camera around a little bit.
Other tips and tricks
Also important: don't underexpose too much. This might result in one of the layers not showing at all. That also goes for shooting in low contrast areas or areas that are too dark. Try to keep your camera horizontal. I have made this error several times in the past. If you use both horizontal and vertical shots during a film swap, the results are usually very messy. If you want to try and line up the film for a film swap, you can use a marker to mark the first frame. That way the next shooter knows how to line up the film. Warning: this does not work for redscale flips, as the entire film gets flipped around.
If you are interested in doing a film swap with me send me an email. I'm always interested! You can also join the Facebook group I've created.