Preserving glass plate negatives

Glass plate negatives are subject to unique damage and deterioration.  Glass is very fragile and can easily crack or break, the emulsion on the glass can flake and the glass plates are also subject to damage from water, fungus and mould.  The risk of damage and the rate of deterioration of glass plates negatives can be greatly reduced if correct storage techniques and handling methods are implemented.

Thanks to support from the Heritage Lottery Fund, the glass plate negatives from the George Street Photography Collection have each been digitised and are now being rehoused into archival standard packaging by our team of project volunteers.  The process we are carrying out is described below.

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Glass plate negatives in their original paper envelopes

Handling, cleaning and rehousing glass plate negatives

Glass plate negatives must be handled on a clean, flat, dry surface.  At St Helens Local History & Archives, we work on top of a sheet of Plastazote, a non-reactive dense foam that reduces the risk of damage.  Plastazote can also be cut to size to separate and protect the glass plates once housed in storage boxes.

Gloves should always be worn when handling glass plates, to increase grip, prevent fingerprints and also any physical injury from the glass.  Non-vinyl nitrile gloves are recommended as cotton gloves can be slippery when handling glass and could also snag flaking emulsion.

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1. Take a glass plate negative.  This George Street Photography Collection includes mostly 4″ x 5″ glass plate negatives.

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A glass plate negative in its original envelope

2. Remove the glass plate negative from its envelope in order to identify the image.  Always handle glass plates by two opposite edges, never one edge or a corner.

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Always wear gloves to handle glass plate negatives

3. Once the image has been identified, write the new reference code and title onto the new enclosure.  This should be written before housing the plate, to avoid putting pressure on the glass.

The glass negatives from the George Street Photography Collection are being rehoused into acid-free pHoton four-flap paper enclosures.  Glassine, PVC or coloured envelopes should not be used as they are not a suitable storage medium for long-term preservation.

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A pHoton four-flap cruciform paper enclosure

4. Remove any dust or debris from the glass plate using a soft, natural brush.  Care must be taken on the emulsion (dull) side of the glass plate.

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Carefully remove dust and debris

5. Close the four flap enclosure onto the plate.  When folded, the enclosure forms a secure unit around the plate without the need for glue.

 

6. Place the negatives in their new storage box vertically on their longest edge – this puts the least pressure on the glass plates.

The below shows temporary storage.  The glass plates from the George Street Photography Collection will be eventually housed in Premier Hinged Lid Boxes, 1300 Micron, 132 x 164 x 118mm.

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Glass plate negatives must be contained in stable, dry and cool storage conditions.  The glass plates from the George Street Photography Collection will be stored on static stainless steel shelves within monitored conditions, between 16 – 18Β°C and between 35 – 45% relative humidity.

There are various resources for more information on the preservation of photographic materials, for example: The National Archives ‘Caring for Your Photographs’, The British Library ‘Preservation of Photographic Materials’ or The National Media Museum ‘Conservation: Glass Negatives’

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