Will slide colours start to fade with intensive use.

If you work out the exact number of hours of projection over the show then divide that by 80 you will find the total time a single slide is projected for isn’t that huge.

Regardless, it is true that all colour photographic slides will fade eventually. The degree of fading is difficult to predict as it depends on relative humidity, the length and intensity of exposure to light, particularly at both ends of the spectrum (infra-red and ultraviolet). Projector design (ultraviolet and infrared mitigation) and lamp type all play a part.

Modern colour films control the colour dye fading well. In other words, the spectrum of dyes fades fairly evenly and gradually, and doesn’t lead to noticeable colour shifts. This means that it is less noticeable to an audience – especially as they don’t know what the colours should like, only the author.

Our test show that the highlights (clear) areas of film will begin to darken and yellow. Conversely, the shadows (blacks) will lighten and become brownish. Even with a degree of fading it may not be noticeable to an audience – except if confronted with a comparison of an unprojected slide to a ‘well used’ one.

In practical terms, in museum multi-projection shows in the 1980s, when the on-screen viewing experience got too bad the whole lot were replaced (never replace individual slides as that looks terrible) and that may have been on 3 month or even six month cycles.

So back to the original question you ask ‘will the slides hold up over that period’ – the true answer is they may do but it depends. But more than likely it will be fine. And if it isn’t, then valuable originals haven’t been destroyed, just order a new set and the issue is sorted.