Studies on the useful life expectancy of magnetic media, such as video and audio tape, have indicated that the soft resin that binds the magnetic particles to the carrier tape is the most susceptible to ageing through oxidations and hydrolysis. Experimental work on artificially aged tapes does not seem toadequately predict the lifetime of such tapes; determining when a tape collection should be copied is a matter of guesswork. Such guessing can lead to either expensive and unnecessary copying of healthy tapes, or the loss of information due to tapes deteriorating sooner than expected. A previously unused method is presented for determining the state of deterioration of videotape, using Fourier-transformation infrared (FTIR) microscopy, and work in progress discussed.