Humidity – the challenge.

Humidity – the challenge.

I have been asked to write about some rather dry subjects but without a doubt this would have to be considered the driest to date. Ironically this discussion is about the book and paper collectors’ greatest enemy second only to fire….humidity.

Cat_static_too_dryIn my life pre books, ephemera and fine art my greatest concern with humidity was that it made my hair frizzy and my skin sticky and sleeping uncomfortable. The only time I was concerned with too little humidity in the house was when I would walk across the room and then stroke one of our cats which if it was too dry would result in a spark launching Dickens, Bustopher or Nell from a warm curled up fluffball enjoying their happy dozy nap into a static crazed missile blasting across the room. Needless to say this placed somewhat of a strain on the relationship with the felines in the household. Sadie and Tanner, our golden retrievers on the other hand would just take the spark roll over and enjoy the belly rub. Cats are such drama queens.

Books and ephemera are a lot like cats when it comes to relative humidity, they both over react. However in the case of valuable books and paper the reaction to relative humidity can mean the difference between a sale or non sale, a thousand dollar sale to a hundred dollar sale and the loss of a formerly fine piece due to damage caused by poor storage.

Antique_books_humitity_effectWhat is the first thing you notice upon entering an old book shop? The smell. As endearing as that musty, “old book” smell may be, it is a huge red flag indicating the environment is damp, a death knell for books and paper. That charming musty smell is mold and there is nothing glamorous about that.

Mold produces gasses. Many of these gasses are odorless but some have a musty odor, the smell typically associated with mold. It’s important to realize that if you smell the musty odor of mold, that means you are inhaling compounds produced by the mold and are probably also inhaling mold spores. Some of those compounds are toxic.

moldYes books and paper are important but so too are the people in the environment Mold, can cause a wide range of medical problems such as difficulty breathing, sinus infections, bronchitis, pneumonia, migraines, sore throats and inflammations are just a few of the potential health concerns as a result of inhaling mold spores.

Another enemy of the book and paper collector that is a result of fluctuating or humid air is foxing. Foxing is the name for the splotches, spots, and specks you often see on older books. It is rare to find a book from the eighteenth or nineteenth century that does not show signs of foxing.

foxingThe best way to prevent initial or further foxing on your rare books is to store them properly. Books should be kept in a cool, dry place. Libraries and museums maintain a relative humidity of 50%, which halts foxing altogether. At home, use the following techniques:

  • Store your books thoughtfully. Keep them in a room that has central air conditioning and heat. Digital versions are reliable and affordable.
  • If you live in a relatively humid area, consider using a dehumidifier.
  • Always use acid-free paper if wrapping, packing, or mounting rare books and ephemera. Foxing changes the pH of the paper, and additional acid can cause further degradation.

The collections at LDRB are safely ensconced in a climate controlled environment in which the temperature is set at 70 degrees all year round. The relative humidity is kept as close to 45% as possible and is monitored constantly. It is kind of like living in a wine cellar but without the obvious benefits.

wine_cellarSince January of this year, In order maintain optimum relative humidity and eliminate fluctuations in humidity we have replaced the furnace, the air conditioner, removed the hot water heater and replaced it with a with a dual boiler which delivers domestic hot water to the faucets and also maintains the in floor heating. All this and the VanEE air control system are responsible for keeping all books, paper, cats, dogs and humans very safe and comfortable.

If you would like to read further on this subject and learn more about how to keep your collections safe from the horrors of relative humidity, the following is an extremely good article from the Northeast Document Conservation Center:,-relative-humidity,-light,-and-air-quality-basic-guidelines-for-preservation


Article written by Julia McLaren, The Lord Durham Report editor

© text  Lord Durham Rare Books, all rights reserved.

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