There have been several threads on photo.net about rescuing old negatives and slides that have become infected with fungus. I have seen it suggested that cellulase (an enzyme that digests cellulose, of which plant cell walls are made) might work; but conversely that fungal cell walls are made of chitin, not cellulose. One published procedure (http://cool.conservation-us.org/byorg/abbey/an/an26/an26-5/an26-512.html ) was complicated, included a period in the freezer, and involved the use of ammonia, which I would have expected to endanger the dyes of colour films. So here is a description of a very simple procedure that worked for me. I hope it will help others.
I had some Kodachrome and Fujichrome 35mm slides from the 1970s to 90s that were covered in unidentified fungus. I could scrounge some cellulase from a school laboratory, but not chitinase (if such a thing exists). I know little about the mode of action at a molecular level, but thought there was enough similarity in the molecular structure of cellulose and chitin (they are both polysaccharides) to make it worth a try.
I diluted the cellulase (Novozymes ‘Celluclast’) 1+99 with tap water at room temperature. (So you only need a very small amount, and I re-used 100 ml of dilute solution repeatedly over a week or so, storing it in the fridge between times.)
I immersed the (unmounted) slides and after a couple of minutes soaking, I very gently rubbed both surfaces with my fingers. (I did this after washing the dishes by hand, to make sure my hands were clean and grease-free!) It was immediately apparent that the slide was coming cleaner. I left the slides soaking for a further 5 minutes, rubbed them very gently again, then decanted off the dilute cellulase. I rinsed the slides thoroughly in tap water to remove floating debris. Then as a precaution against re-infection, I gave the slides a final rinse in Tetenal’s Mirasol wetting agent, which includes an anti-fungal component. I dried the slides emulsion-side up on absorbent paper.
I attach images of the same slide before and after treatment. You can see that there is still some debris on the treated slide, but the task of digital retouching is vastly reduced compared with pre-treatment. Nothing else seems to be affected, and there is no sign of the emulsion being eaten away or tunnelled by the fungus. There are no scratches caused by handling, either.
It seems a little odd that this works, because at least some saprophytic fungi produce cellulase themselves, in order to break down the plant structures they feed upon; so you’d have thought they’d be immune to its effects. Furthermore, ‘Celluclast’ is prepared from a fungus! But while it would clearly be nice to understand, it’s not strictly necessary, given that this really did work. If, like me, you have treasured images that seem beyond hope, this is definitely worth a try.
I had some Kodachrome and Fujichrome 35mm slides from the 1970s to 90s that were covered in unidentified fungus. I could scrounge some cellulase from a school laboratory, but not chitinase (if such a thing exists). I know little about the mode of action at a molecular level, but thought there was enough similarity in the molecular structure of cellulose and chitin (they are both polysaccharides) to make it worth a try.
I diluted the cellulase (Novozymes ‘Celluclast’) 1+99 with tap water at room temperature. (So you only need a very small amount, and I re-used 100 ml of dilute solution repeatedly over a week or so, storing it in the fridge between times.)
I immersed the (unmounted) slides and after a couple of minutes soaking, I very gently rubbed both surfaces with my fingers. (I did this after washing the dishes by hand, to make sure my hands were clean and grease-free!) It was immediately apparent that the slide was coming cleaner. I left the slides soaking for a further 5 minutes, rubbed them very gently again, then decanted off the dilute cellulase. I rinsed the slides thoroughly in tap water to remove floating debris. Then as a precaution against re-infection, I gave the slides a final rinse in Tetenal’s Mirasol wetting agent, which includes an anti-fungal component. I dried the slides emulsion-side up on absorbent paper.
I attach images of the same slide before and after treatment. You can see that there is still some debris on the treated slide, but the task of digital retouching is vastly reduced compared with pre-treatment. Nothing else seems to be affected, and there is no sign of the emulsion being eaten away or tunnelled by the fungus. There are no scratches caused by handling, either.
It seems a little odd that this works, because at least some saprophytic fungi produce cellulase themselves, in order to break down the plant structures they feed upon; so you’d have thought they’d be immune to its effects. Furthermore, ‘Celluclast’ is prepared from a fungus! But while it would clearly be nice to understand, it’s not strictly necessary, given that this really did work. If, like me, you have treasured images that seem beyond hope, this is definitely worth a try.
