The pannotype mystery: using science to research early photographic processes

This year we are again using the wonderful opportunity of British Science Week (6th – 15th March) to showcase brilliant examples of heritage science work being undertaken by NHSF members and across the sector more generally.  We will post new blogs throughout the coming week. 

To launch the series, we have a post written by Ioannis Vasallos, Conservator of photographs and paper at The National Archives, all about the analysis and conservation of rare photographic processes.

The National Archives has an estimate of eight million photographs in its collection. Some of the very early ones can be found on the Design Registers, which contain almost three million British patterns, products’ designs and trademarks from 1839 to 1990s (figure 1). As part of a larger project to understand, conserve and improve access to the Design Registers, Collection Care has been doing research and analysing some rare examples of early photographic processes found amongst them.

Pannotype is an early photographic process invented in 1850s, and used only for a short period of time till the 1880s. Photographs made with this process are rare in collections, and it is therefore exciting to have found 15 pannotypes in a bound volume of the Design Registers (figure 2). These photographs depict designs of ceramic houseware but many of them cannot be accessed due to their deteriorated image layer which has become tacky, and caused other designs to stick on them (figure 3).

A series of analytical techniques were performed in order to understand the composition of the image layer, as well as the rest of the materials that the photographs are made of. Elemental analysis was done with X-Ray Fluorescence spectroscopy (XRF) and showed us the presence of silver particles (figure 4), which confirms the photographic nature of the image. Lead was also detected and seems related to the manufacturing of the cloth support that the pannotypes were placed on. Fourier Transform Infra-Red spectroscopy FTIR analysis identified a natural resin on the photographs whose image layer is degraded, and collodion on others whose image is not affected (figure 5). The analysis helped to combine literature review of historic photographic journals and photographic recipes in order to cross reference the materials that were identified. Finally, the newly acquired Multispectral Imaging system (MSI) was also used to enhance the visibility of the images on the pannotypes whose surface is covered by stuck pieces of paper (figure 6 & 7).

This will now inform the decision making for the conservation of the photographs whose image is degraded and have paper stuck on their surface. The information gained will also enhance the understanding of historic photographic practices helping to preserve similar photographs in other archives and collections.

To find out more about the work of Collection Care you can check the blog of The National Archives at https://blog.nationalarchives.gov.uk/, or you can contact Ioannis Vasallos, Conservator of photographs and paper Ioannis.Vasallos@nationalarchives.gov.uk

NA figure 1
Figure 1: BT 43/67, an open page in a volume from the Design Registers. © The National Archives.
NA Figure 2
Figure 2: BT 43/67, pannotype depicting pottery. © The National Archives.
NA Figure 3
Figure 3: BT 43/67, Group of pannotypes with paper stuck on their surface. © The National Archives.
NA Figure 4
Figure 4: XRF analysis on a pannotype photograph. © The National Archives.
NA Figure 5
Figure 5: Conservation scientist, Lucia Pardo Pereira perform FTIR analysis on a pannotype photograph. © The National Archives.
NA Figure 6
Figure 6: BT 43/67/130678, true colour image captured with MSI. © The National Archives.
NA Figure 7
Figure 7: BT 43/67/130678, infrared reflected (IRR) image captured with MSI. © The National Archives.