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Cleaning, Scanning, Digitizing and Rehousing: A Journey with Glass Plate Negatives

Part II: Preservation Process

Table with materials. September 2015, Kristin Cook.

I had a medium-sized table in a corner of the staff room, where I pulled down the shades to keep sunlight from fading or otherwise damaging the images on the plates. To my left, a side table with a set of drawers contained the materials I would need to work on the plates. These included cotton balls, cotton rounds (pads), a few soft-bristled, unused paint brushes, one gallon of distilled water, plastic cups for the water, latex gloves, a notebook, a flash drive, a ruler, a pencil, double-sided tape, and scissors. On top of the desk we placed blotter paper (later changed to Mylar, as it was deemed more effective) to keep the table from getting wet or dirty during the cleaning process.

I decided that the “beginning” of each crate would be the right-hand side if I were looking at the crate as it appears in the photo below. That would be where I would start the cleaning, and I would then keep the plates in the order in which I found them, and scan and number them in the order in which I had found/cleaned them. To safely clean the glass plate negatives, my supervisor and I decided to follow the instructions available from West Virginia University Libraries at

Emulsion side of a plate ready to be gently brushed. September 2015, Kristin Cook.

To begin, the person cleaning the negatives should wear clean nitrile or latex gloves. The distilled water should be poured into one of the cups, and placed so that it cannot be spilled onto the surface where you are cleaning – I put it on top of the side table, as it was lower than the main table I was working on and there was no way that if the cup spilled, the water could get on my table and harm the glass plate. Next, take a plate from its current storage, being sure to handle every plate with two hands every time. The plate to be cleaned should be placed emulsion-side up on a clean, flat, dry surface.

Determining which side is the emulsion and which side has plain glass can be a bit difficult. Sometimes the emulsion (the chemicals that created the negative image on the glass) is flaking off, or has a bumpy texture, so it’s easy to determine. But sometimes the emulsion has leaked onto the other side, or the emulsion is in very good condition and is just as flat and smooth as the plain glass slide, and it’s more difficult to determine which side is which. If you’re having difficulty, place the plate down on the table, and take a moment to see how clear it looks to you. Now gently flip it over, and if the other side is clearer, that is the glass side. But if the second side is cloudier/duller, that one is the emulsion side, and the one you should start with.

Take a soft, unused paintbrush and very slowly and gently brush over the plate from the center outward, never inward. Dirt, dust, and cobwebs should come off of the plate, but emulsion should not. If emulsion starts flaking off of the plate, stop cleaning it the way that you are and see if you can use a different, gentler motion. If this is not possible and you continue to contribute to loss of emulsion, stop cleaning that side of the plate! When that side is finished, turn the plate over so that the glass side is facing up. Dip either a cotton ball or cotton round into the cup of distilled water so that it is about 1/3 of the way wet.

Gently cleaning the glass side of a plate with a cotton round dipped in water. October 2015, Kristin Cook.

Keeping the cotton round flat, slowly and carefully work from the middle of the plate out toward the edges to clean the dirt, dust, etc. from the glass side of the plate. It is very important that water does not get on the emulsion side, as water washes the emulsion away and will cause the image to be lost forever. It may take more than one cotton round (I prefer these to the cotton balls, as the balls can be streaky and leave cotton residue behind) to completely clean the glass side, depending on how dirty it was. Or you may wish to use a second round to dry off some of the water that was used with the first one, and find that it brings up more dirt and debris. I will often use a second or third cotton round to go over the edges of the plate (holding the plate in my hands) because the edges are often the dirtiest part of the plate. I do this dry though, not wet, as a way to protect against possibly getting water on the emulsion side of the plate.

After cleaning, the plates need to dry. My supervisor found an example online of how one organization stored glass plate negatives while drying, and it quickly proved to work effectively: In a file box, hanging file folders were spaced apart and the plates were given enough room so that none of them were touching. The glass plates air dried in this manner fairly quickly, and then could be moved in their box into the main office to be scanned into the computer.

Part I: Introduction                                                                                                       Part III: Digitizing, Cataloging, and Re-Housing