Behind the scenes; conservation in progress

Do you ever wonder what is happening to sticky tape? The answer is usually “No” and for a good reason. We all believe that it will remain nice and sticky for eternity! Especially nowadays when we have so many choices of self-adhesive tape or pressure sensitive tape with excellent qualities too; there are transparent, matte, colour, black, white, brown, red, archival ones, linen ones and so many more. The point is that we don’t think twice when it comes to applying it because we are confident about its short term effect and result. Well, I will try to change your mind a bit and show you how a well-intended attempt to stick together broken glass plate negatives turned into a painstaking nightmare.

In the mid-19th century, photographic negatives began to use glass as a support. Glass provided a sharper negative and a more detailed positive print, and soon replaced paper negatives. Like photographic prints, glass negatives are composite objects, consisting of a glass support, a binder, and an image-forming or recording substance. At the BPMA we store approximately 2500 glass plate negatives dated from 1930s to the 1950s with a variety of topics from day to day postal operations. 89 of them are damaged, with broken and/or missing parts. A common practice of preserving a broken glass plate negatives was to sandwich it between either one or two new glass plates and apply a tape around their perimeter to secure them. The quality and type of tape used varied but one thing was certain; the intention of the ‘restorer’ could only be described as a noble attempt to save what was broken.

Taped Glass Plate negatives

Taped Glass Plate negatives

Unfortunately, good intentions don’t always have the result we hoped for. So when the need arose to remove the tape, I faced a big challenge. The adhesive of the tape had permeated the emulsion layer of the glass plate negative, it had cross-linked as we say in conservation (a chemical process of bonding one polymer chain to another). This new type of bonding creates irreversible damage as it discolours and fades the image but mostly because it weakens the emulsion layer and makes it prone to flaking, putting the image at risk. Any mechanical attempt to remove it went downhill so the next idea was to use an aqueous and a chemical treatments which mean the introduction of liquid either water or solvent. I used a microscope to avoid any unnecessary contact between emulsion and water –these two things do not like each other very much.
All geared up with a microscope, a portable air extraction unit, solvent and water, apron, I have started the process of slowly moistening the tape and carefully removing it with a dentist’s spatula.

During removal. residues from adhesive stuck on surface

During removal. residues from adhesive stuck on surface

To remove tape from one glass plate negative of 80 x 100cm in dimension I have estimated it took from 14 to 20 hours. On the other hand, I have timed how long it took to apply a sticky tape on one glass plate negative mock-up of the same dimension and it took between 1-2 minutes. Pretty amazing don’t you think! Consequently in a collection of 89 damaged and taped glass plate negatives it took 3 hours to apply the tape and it would take 1780 hours to remove it, which is 254 working days! Makes you wonder why conservation sometimes can take so long!

After Removal of tape

After Removal of tape

In conclusion, I would like to emphasise to all lovely collectors out there who value and protect their collections that if you think a quick fix might solve your problem, please think twice. Besides if you are unsure about a procedure please contact a conservator who will be able to advise you and guide you to a suitable solution. In the long term, it will be a less costly and time consuming operation and it will save your precious collection for future generations to enjoy.

Before and After Conservation

Before and After Conservation

Katerina Laina ACR, MSc
Assistant Paper Conservator

2 responses to “Behind the scenes; conservation in progress

  1. Katerina, good morning.
    I am the volunteer Keeper of the Historic Photograph Collection in a museum Whilst I do not have the problem you describe here, I am looking to store a number of different sized glass plate negatives correctly. Could you advise me of a suitable supplier of quality storage material for these plates?
    thank you
    Dave

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