Filters for IR photography can be very expensive, with the Hoya filters going for over $100. I paid less than that for most of the cameras that I have, so this put me off of trying IR photography for quite some time.
One day, I was playing around with my IR goggles in the darkroom and realized that all of the Lee color lighting gels in my swatchbook appeared crystal clear under the IR goggles. By stacking up a red, green, and blue gel, I made a filter pack that was nearly opaque to visible light yet still appeared totally clear to my IR goggles. It only remained to be tested how well the IR cutoff of the Lee filters matched the spectral sensitivity of modern, inferior IR films. My first test is very encouraging, with a gratifying Wood effect.
Shown for reference is a picture with no filtration, followed by a picture shot with a RGB gel filter pack. Click the pictures for full-size.
Film:Efke IR820 Aura, 35mm
Exposure: Texas sunlight, f/16 at 1s (filtered), 1/60s (unfiltered)
Developer: Xtol 1+2, 15min.
Printed on Fomaspeed Variant 5x7 paper and scanned on Epson v500 using iScan in Linux