Effect of humidity fluctuation on a rare book

Which is why conservators, collection managers, etc. are so adamant about environmental control in collections storage and exhibit spaces.

Low Relative Humidity- In Pictures!

Conservators spend a lot of time talking about how environmental conditions can affect the overall stability of an artifact.  Our training includes reading many, many articles and case studies that document how fluctuations in temperature and relative humidity (RH) can cause dimensional change in an artifact and increase the rate of chemical decay.  High RH can cause a book to expand and is an even bigger factor when it comes to the chemical reactions that cause paper to degrade.

Low relative humidity is also a concern.  If high RH can cause a book to expand, low RH can case a book to shrink and warp.  Since a book is made of several different component parts that will respond to RH fluctuations at different rates, keeping books and artifacts at a stable RH is crucial.

These facts can be a little abstract and when sharing them with colleagues as I advocate for the care of the Library's collections, it can be difficult to convince people that a book that has survived hundreds of years without environmental control is still susceptible to low RH.  So I was particularly horrified and delighted on a recent cross-country plane flight when I noticed that the book I had brought with me, Maurice Craig's "Dublin 1660-1860" had started to respond to the low RH (10-12% at best) almost two hours into my flight.  Note how the covers have warped away from the body of the text block (pages).  The book had been completely flat when I packed it that morning.  I had been reading it during the flight and only noticed the warping when the flight attendant gave me a cup and I put the book down on the tray table.  I took the picture to make sure I wasn't mis-remembering the condition of the book and resolved to compare it with the condition of the book once I had returned home and the book had a chance to re-adjust to my air-conditioned home in Charlottesville.

My flight had been on Wednesday, August 7th, leaving SFO at 1pm Pacific Time.  The picture at right was taken Friday, August 9th about 8am Eastern Time.  Note how the covers are no longer warping away from the textblock.  Remarkable!

The low relative humidity on the plane is extreme, but it isn't uncommon.  The winter time RH for the Northeastern United States is often in the mid to low teens and collections that are housed in areas that don't have supplemental humidity control are at risk.  Most libraries address the need by keeping their fragile books in boxes.  I was going to return this book, but maybe I will renew it through the winter to see whether we need to make a box.

Exhibit Standards

Exhibits are great way for libraries to raise awareness about the gems in their collections.  An exhibit can showcase a little known collection of letters or highlight specific details within a well known story.

Exhibits can also be a lot of work, it is hard to pull together the right set of documents to tell a story and then write concise yet informative labels that bring everything together.  Displaying collections is also trickier than it seems.  You want to be certain that your exhibit area has good, stable environmental conditions in terms of temperature, relative humidity and lighting.  You want to be sure the cases seal so that the objects are free from dust and tampering.  There are a lot of details to address, but the good news is that there are standards available to help anyone involved in the exhibit process. 

The National Information Standards Organization publishes free technical leaflets, including "Environmental Conditions for Exhibiting Library & Archival Materials" [Z39.79-2001] which is available as a free, downloadable pdf. from their website.  The link to the pdf. is in the lower left corner of the linked NISO page.  These standards can be particularly useful for those who do not have a conservator or exhibits preparator on staff.

One commonly overlooked detail is a backing board for paper documents.  Many institutions re-use Plexiglas cradles from one exhibit to the next, and this makes a certain amount of sense as it eliminates waste and saves money.  Of course, paper documents come in many different sizes, so a cradle from a previous exhibit will often have to be modified.  Take a look at the picture below, and see how the document is taller and wider than the Plexiglas.  This may not seem like a significant amount, but this is 400 year old paper that has seen a bit of wear and tear over the years and if left on display without proper support, the letter could start to curl and droop over the edge of the Plexiglas cradle.  Why take that chance?

see how much the document hangs over on the left and at the top?

All that you need to do is take a piece of archival mat board and trim it so that it is just a few millimeters longer and wider than the original document, and then strap the document to it with polystrap so that it doesn't shift while you're opening and closing the exhibit case.  This is very easy to do and will make a tremendous difference in the long term preservation of your collections.

mat board trimmed to size

Chapter 8 of the NISO standard has all the basics for safe display of flat paper items, and the rest of the document has very useful information for bound volumes, lighting, etc.  So go ahead, check it out!