The Home-Made Filter
The poor man's filter is a poor choice.
There has been several reports that using exposed and developed film works as an infrared filter.
The theory is that the film goes jet-black thus blocking visible light but allowing infrared to pass. This is true to a certain extent but in practice the results are so poor it's not worth the bother.
The home-made filter typically begins transmission at around 710-730nm but requires several layers resulting in a blurred image. The film is very difficult to mount in a filter ring and 35mm film is not quite big enough for a 37mm ring and even more so for a 43mm ring.
Pictured above are two different brands of film which were exposed to several minutes of bright sunshine before being developed. The result was barely effective and I can recommend you save your time and money (not to mention the strange looks you get at the developers) and buy a proper filter.