Film. This is the key ingredient to this whole deal. This needs to be unexposed and undeveloped, at least to start out with. Make sure that the film you use is large enough that, once developed, it will be large enough to cover the end of your lens. If you’ve truly gone all digital and don’t have any film lying around, ask some friends, or suck it up and buy a whole roll from the store. You only need a single piece.
Failing that, here’s a creative use of your old floppy disks, as the actual floppy part of the disk filters IR light.
Scissors. Nothing fancy—just something you can use to cut up film.
Old Filter. If you don’t want to be holding this up to your lens with your hands the whole time, then finding an old UV or clear filter would help streamline the process considerably. You won’t be removing the old filter plastic/glass, so it has to be clear and free from scratches. Depending on whether you want to reuse this filter, you can also get a touch of glue that won’t expand as it dries to fasten the IR filter to the old filter, and/or black tape to prevent visible light seepage from around the edges.
The theory behind this is simple: develop completely exposed film, so that you have a filter that is completely opaque to visible light. This means either using those blackened tailends of old developed film - probably too small to be useful- or simply leaving the film out in the light for a while to expose on its own.
From there, you need to get this developed. If you have access to a film lab and you know how to use it, great! If not, find a local store that can develop film for you. The people at the shop might be a bit confused as to why you’re developing completely exposed film, so having a chat with them and/or writing a note to accompany your film is probably a good idea so they don’t just toss it. Many places won’t charge for this, but don’t count on it.
If you’re using a floppy disk, then just take it apart, and remove the floppy black bit from within. This will be your filter. In both cases, be careful not to scratch or otherwise smudge your future filter during the handling of them!
From here, you need to make some sort of filter mount. This article outlines a number of ways to do this, one of which will hopefully match you and your camera. A special consideration for IR filters is that there can be no gap between the IR filter and the mount itself through which visible light can leak through to your sensors - otherwise, the effect will be ruined, IR photography contaminated. Opaque glue, black tape, sharpie - do whatever you have to do make sure no light can get through! Multiple layers of your IR filter might also be a good idea, just to make sure. It certainly can’t hurt.
Beyond that, you’re pretty much done!
Using The IR Filter
Having manual control on your camera is really a must to make this work right. Because you have no visible light to work with, you’ll be needing to take long exposure shots for this to work, and you’ll need control for this to work. In addition, most autofocus mechanisms will be confused by the existence of the IR filter and try and focus on the filter itself, which is obviously not want you want it to do. Also, if you don’t want to do all your white balance adjustment during post processing work to get rid of that red haze, setting a custom white balance will save you some time. Manual is your friend for IR photography!
The process will also be eased along by the existence of some sort of stabilizing device, typically a tripod, for those long exposures.
Keep in mind that IR photography is largely restricted during the day, just because of the warmer temperatures and thus more IR radiation available.
Infrared sensitivity varies by camera, so it may be that this won’t work as well for your camera as for your best friend’s. Also, take note that you’ll be shooting in the near infrared, which is what most IR photography consists of, as opposed to far infrared. As the names suggest, near infrared is closer to the visible spectrum than far infrared.
Other than that, use your creativity, and explore this strange new world! IR photographers love to take pictures of snowy-white vegetation and the like, but there’s a lot more to IR photography than just that: think of all the odd heat signatures in an urban environment, or of animals and people, or…
Check out this article for more tips on how to do infrared photography.
Different combinations and amounts of developed unexposed film and floppy disk may work better for different cameras, and the materials are cheap enough that it’s worth exploring your options.