Conserving the Collection: Blocked Negatives and Investigation Techniques

Today’s post comes from Emma Bonson, one of our wonderful conservation team and is a follow on piece to one written by Sarah Allen back in July about delaminating emulsion on our glass plates.

We’ve been very lucky to work with Sarah and Emma who have bent over backwards to try and solve some of the issues facing our plates. By forming a partnership with the University of Lincoln, which sees the collection act as a training resource for conservation undergraduates, Sarah and Emma have not only ensured that our budget will stretch to stabilise the entire collection, but have also secured a unique opportunity for students to work hands on with this kind of material, hopefully inspiring some of them to specialise in photographic materials as they advance in their careers. It’s a collaboration of which we are very proud, and grateful to Sarah and Emma for establishing.

Over to Emma….

 My name is Emma Bonson and I have been working alongside Sarah Allen to help conserve the Knights-Whittome collection. Sarah told us all about the treatment we carry out on the negatives with peeling emulsion in her previous blog post and I am now going to describe another conservation issue within the collection that we call ‘blocked’ negatives. This is where the original envelopes have stuck to the photographic emulsion surface when they have been exposed to water and damp conditions in Knights-Whittome studio shop basement. This causes the image on the negative to be blocked and prevents them from being digitised.

The strength of the bond between the envelope and the emulsion does vary within the collection and some can be treated. We have categorised these into those with a strong bond and those with a weak bond.

Examples of a ‘strong bond’ and a ‘weak bond’ negative

To treat those with a weak bond we devised a technique; after some testing, where we humidify the stuck areas of paper fibres with a solution of solvent and distilled water. This enables the fibres to loosen from the surface and they can be gently removed without causing damage to the emulsion and the image underneath.

Before and after humidifaction treatment on the weak bond negative

Unfortunately the negatives with a strong bond can be time consuming to work on in this way and some also have damaged and dissolved emulsion underneath and removal using the solvent solution is not always an appropriate method.

We have been investigating methods to enable us to see the image underneath the envelope without having to remove it. Working from the university conservation labs in Lincoln, myself and the student volunteers have been lucky enough to use some of their specialist equipment and we are going to share our discoveries in a few different blog posts…this one will be about the X-Ray machine.


Using the X-Ray machine at Lincoln University conservation department

The X-Ray is normally used so students can discover what is inside their objects they are working on during their studies and how they are made. For example what kind of structure is inside a doll or a piece of taxidermy or perhaps how a ceramic jug has been previously repaired with metal rods. So we were hoping we might be able to see beyond the envelope to see the details on the emulsion of the blocked negative. The image on the negative is made up of silver particles on a thin layer of gelatin which in photographic terms is the emulsion layer and because there are these silver particles we were hoping the X-Ray machine would pick up these and the image they create. We made several adjustments with a variety of settings and different exposure times with help from Jo Wright who is the science technician on the conservation course at Lincoln but unfortunately we didn’t have any success.

image006The X-Ray did however see through the envelope and picked up the shape of the negative inside it and also highlighted the damaged marks where the envelope had bonded to the emulsion – this was not quite the result we were hoping for!

Although it was disappointing that this experiment did not work in the way we had hoped, it was exciting to use the X-Ray machine and we are going to continue to explore this research further. We are also looking into infra-red photography and Ellie; our brilliant work placement student is going to tell us about how we used the Multi-Spectral Imager in her next blog post.

Ellie’s post will appear next week…


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