Degraded slide cases

OBJECT OF THE MONTH JUNE 2025

Our object of the month is a set of transparent plastic slide sleeves, the kind used for decades to store slides. But what was once intended as a simple solution has now revealed itself as a conservation problem: The adhesive strips on the sleeves, presumably applied in the 1970s or 80s, have become brittle, their originally transparent adhesive layer has yellowed, cracked, and in some places runs in a wavy pattern across the surface. This deterioration is accompanied by milky spots and streaks – a visible trace of chemical processes that have altered the material over decades.

These are indeed typical signs of aging in non-archival-quality plastic: oxidation, loss of plasticizers, and the formation of acidic decomposition products such as acetic acid not only attack the material itself but can also damage adjacent archival materials in the long run. In chemistry, this phenomenon is called degradation. The slide sleeves begin to warp and become distorted—some can hardly be opened safely without endangering the contents.

The cases tell their own story – of pragmatic decisions, of material changes – and of the responsibility that lies in dealing with these traces today. In an ongoing project, the affected cases are currently being gradually removed from the collection, their contents transferred, and secured in archival-quality polyester film. A laborious but necessary step to preserve the delicate photographic material.