This past May, I attended a workshop on humidification and flattening techniques for documents at the Preservation Lab inside University of Cincinnati’s Langsam Library, with two of my colleagues, Teresa and Carla. The workshop was held by the Ohio Preservation Council and was led by Kathy Lechuga, a book conservator at the Indiana Historical Society. We were very excited about what we learned and immediately started gathering what we needed to practice these techniques. Our results have been very promising and we wanted to share some of the techniques we put into practice as well as some of our results.
With archival collections we often receive several rolled documents and photographs. Flattening documents dry is ideal. It is the least risky flattening method to use since it does not involve introducing any foreign elements to the item. If the item can be gently unrolled without forcing or damaging it then flattening dry is possible. This involves placing the item under Plexiglas and weights or placing it in a press. However, if the item won’t unroll easily it helps to slowly humidify it. At the workshop we were shown three methods of humidifying documents and photographs. Teresa and I have started working with two of these methods.
The first method involves a humidification chamber, using clear plastic bins, egg crates, distilled water and blotter paper. We cut the egg crates and blotter paper to fit the inside of the bins. With a clean spray bottle filled with distilled water we lightly sprayed the blotter paper; the paper must be damp, not soaked. The dampness of the blotter paper determines how quickly humidity is introduced to the item. The more delicate the item the slower we humidify. The fragility of the item and the dampness of the blotter paper will also affect how often you will check on the items you are humidifying. Once the blotter paper is damp we lay it at the bottom of the bin, place two supports on top of the paper, and then the egg crate on top of the supports. You can use thick pieces of clean plastic for the supports;we layered leftover pieces of the egg crates. The document is then placed on the egg crate and the bin is sealed. You may want to check on the item more or less often
depending on the thickness of the paper. A good way of measuring the humidity level is by using humidity cards. Once enough humidity has been introduced, the item is placed between blotting paper and inserted in one of our presses to dry. We then wait a couple of days to a week and periodically check it to make sure that the item is completely dry.
The second method we used is called local humidification. This process is more aggressive and is used for creased paper items. Generally this is best implemented for smaller items since the process is aggressive and can be time consuming. That being said, we implemented this process for a poster that had been folded up and stuck into a scrapbook since the 1930s. After unfolding it we saw that the poster was severely creased. Due to the frailty of the poster, Teresa and I thought it was best to encapsulate it. This required flattening out the creases. For local humidification you need distilled water, a clean brush, thin absorbent blotting paper, a bone, and some small weights. This process involves directly dampening the item, so you want to be careful how much you wet your brush. Obviously the more humid the paper, the better it will flatten. However, putting too much water can also cause staining and tearing.
Needless to say, Teresa and I were very careful the first time we employed this method on archival materials. Once the damp brush is applied it is important to get some blotter paper on the humid area fairly quickly and place some pressure on the paper by using the bone or by placing a weight on the blotter paper. We used a combination of weights and the bone depending on the area of the poster we were treating. Afterward, we placed it in a press between blotting paper.
There are certain things that should be kept in mind when flattening something. Be realistic. If the item is severely damaged or delicate (such as parchment) then you shouldn’t attempt flattening it yourself and consider bringing it to a conservator. For instance, you should leave flattening photographs with cracked emulsion to conservation professionals. Also, consider how flat you actually want the item. Sometimes flattening something can also flatten out the texture of the paper which you may want to maintain. It’s a good idea to practice these techniques on scraps of paper and gradually work your way to archival materials. I also strongly recommend attending a workshop and learning from someone who has experience working with these techniques.
Adria Seccareccia, Processing Assistant