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  • Writer's pictureRebecca Somerset

Caring for Glass Plate Negatives

Back in March 2018 Lorraine Finch, a photograph conservator, gave the archive team some valuable training on identifying different photographic processes and how to care for the different types of photographic material. We were aware that among the various photographic formats held in the Archives there was a collection of glass plate negatives.

Before cellulose nitrate film was invented in 1903, photographic emulsions were made on glass supports, more typically known as glass plate negatives, and this enabled amateur as well as professional photography to flourish. There are two separate glass plate negative photographic methods which both consist of a light sensitive emulsion fixed to the glass plate base with a binder. In 1851, at almost the same time, Frederick Scott Archer (1813-1857) and Jean-Baptiste Gustave Le Gray (1820-1884) produced the first collodion wet plate negatives. Wet plate negatives were produced by spreading a glass plate with collodion, bathed in silver nitrate and then exposed in a camera. The photographer had to wait for the exposure to be completed before the wet plate dried and was protected by varnish. It was almost completely replaced by the more convenient gelatin dry plate process which was invented by Richard Leach Maddox (1816-1902) in 1871. It was a more practical process and was used until the 1950s when it was replaced in popularity by gelatin silver plate negatives and celluloid roll film.

Although the two glass plate negative methods are chemically different from each other, they have similar storage, care and handling needs, which is a relief as I would find it difficult to distinguish between these two types. Presumably our collection is of the gelatin dry plate variety given that this was the more practical and popular of the two formats. Despite there being fewer deterioration concerns with glass plates negatives in comparison to other photographic formats, the fact that they are made from glass makes them fragile. The issues that can be faced with plates is that they are stuck together, prone to mould, emulsion can flake from glass (known as glass disease) and they can suffer from damage to the glass. Following the training I was keen to work with our glass plate negative collection to gain a better understanding of this collection and to improve their preservation.

The first task to be undertaken was a survey of the glass plates to establish the quantity and sizes. I found that we had about 1,800 plates mostly in two common sizes though there were a few odd sized ones. Surprisingly only a few plates appear to be broken despite having been poorly stored, sometimes in large piles meaning there was a lot of pressure placed on the plates at the bottom. About 500 plates were still in their original wooden studio crates. Some of the boxes and individual plates were labelled, but the vast majority of the collection was unidentified.

Having established the size of the collection we were able to order the necessary material to begin a repackaging project, which was finally begun last month. I first created a work board as it is important to avoid putting glass on hard surfaces and plates should always be placed emulsion side up to prevent any scratches to the photographic surface. Care and good handling procedures have to be observed when handling glass plates as they are most vulnerable to breakage during such. Those dealing with plates need to wear nitrile gloves as cotton gloves are too slippery and loose fibres could snag flaking emulsion.

Individual plates are placed in four flap enclosures as they do not use adhesives and eliminate the risk of a negative chemical interaction. A further benefit is that this can allow a researcher to examine the plate without having to slide a negative in and out of an envelope. As there are some standard sizes I have created templates for these to speed up the cutting out process of the individual enclosures. Prior to the plates being put into their enclosure the flaps are labelled with the relevant unique reference number assigned to that plate as we would not want to put pressure on the plate by writing the label on after it has been inserted.

Plates are then stored vertically along their longest edge and placed into appropriately sized sturdy boxes which can support the weight of the glass. Negatives are stored with other plates of the same size to ensure sufficient physical support and prevent edge pressures on any odd sized negative which could lead to cracking and breakages.

Boxes are lined with plaztazote to provide essential support and to reduce shifting within the box. Spacers are placed at regular intervals and any remaining space will be filled with corrugated card board filler pieces to keep plates upright and prevent any movement within the box. It is better to use a larger quantity of smaller boxes than a few large size boxes not only to prevent strain on the boxes and any staff handling the negatives, but also in the unfortunate event that a box is dropped a smaller quantity of plates will be potentially broken.

Further challenges are presented when storing broken plates as these will need to have specially constructed protective enclosures made to align the individual plate fragments in their proper location whilst also having spacers placed between them to avoid further chipping or breaking. So far I have not yet dealt with any broken plates, but plenty of plates still remain to be packaged so no doubt we will have to tackle some broken ones in due course.

As part of the repackaging process we are also creating a finding aid for this collection. Each plate is given a unique reference number and a description of the plate is produced. It has been found that holding the plates up to a blank word document on the computer screen creates a good light source by which to see the images on the plates.

Some plates have existing labels that facilitate identifying the image and the original label is transcribed into the description for that plate for example, GP/58 contained a typed label reading: Set 6 India Slide 36The palace gardens, Jaipur, Crocodiles. Another example is that for GP/1 a manuscript label stated: Cathedral Mylapore: Madras. On doing some further research I was able to identify that this is in fact now known as San Thome Church-St Thomas Cathedral Basilica, Chennai, India. All this information is put into the description to enable researchers to find images of interest to them.

Using a little detective work can also be beneficial when describing the images on the plates. For example, in GP/50 a plaque above the door could be seen and using a small handheld microscope it was possible to decipher the inscription on this as reading: [St Jude's] Entrance Memorial [St Jude's] Sodality.

We are also scoring the plates to identify which might be a priority for a future digitisation project based on its subject. The negatives are an underused rich historical resource and creating digital copies would facilitate access to them. I feel privileged that I can become more familiar with the glass plates through the repackaging of them and hopefully as our understanding of the contents is improved we will be able to encourage its use. It is rewarding to know that the work being done will help preserve them for future generations to enjoy.

For learning more about glass plate negatives and preservation concerns I found

this website had a good overview.

If you would like to know more about our glass plate negative collection or are interested in knowing more about any of our work please contact us.

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