I am excited to share with you some insights about an ambitious archival preservation project that we completed in 2019.
Within our archives, we house a rich collection of photographic negatives that depict the people, places, and events of historic Sunshine Coast. This collection includes the vibrant Helen McCall collection (late 1920s-1950s) and the Glassford Press collection (1970s).
As you may know from your own personal experience, photographic negatives are susceptible to deterioration from fluctuations in humidity and temperature that can threaten their life-span. In 2017, we began researching the best way to preserve photographic negatives. Archivist Marci Beacham Fuller took the lead in conducting this research, and found the Critical Moisture Indicator (CMI) method developed by Smithsonian Institute’s Mark Mccormick-Goodheart. The CMI approach is an accessible, and scientifically proven method to preserve negatives in a cost-effective way.
First, the negatives are housed in archival envelopes and grouped together in bundles. These bundles are packaged inside a Ziploc bag and sealed. Then we place the bundle inside another Ziploc with a piece of matte board that has been heated in an oven to remove all moisture. We call this a “moisture trap”. It is crucial that a low relative humidity (RH) is achieved inside the trap so any moisture that enters the package will be absorbed by the matte board. Inside the second bag, we placed RH indicator cards which will turn pink when a certain humidity is reached. Once the second bag is sealed, it is placed with other bundles inside an archival box and finally, into another moisture trap with another RH indicator card. Now you are ready to place the box in a cold storage freezer at -18°C, a temperature where any deterioration is minimized due to the low temperature and humidity. With the second RH humidity indicator card visible, we can check and make sure that the humidity has not reached threshold levels (~60 per cent RH).
We anticipate that the packages will last approximately 15 years in the cold storage until the matte board has to be dried again. During this time, the negatives will be protected at the highest level of preservation care that we can offer. We would like to thank volunteers Enya Delaney, Kathy Farrell and Elaine Jackson who worked on this project, along with funders the Sunshine Coast Community Foundation and the Museum Assistance Program.