In honor of Preservation Week, our Special Collections Conservator, Natalie Granados is sharing some of the work she does to ensure that all of our collections are getting the care and maintenance they deserve.

Humidity: What Is Damaging Your Collections?

Written by Natalie Granados (@natartlie). Special Collections Conservator – Uconn Library.

How temperature and humidity work together to affect your paper-based objects is a topic that has been discussed and devoured by conservators since the 80s. Join me in this series covering common damages to paper and books such as handling, temperature, humidity, pests and pollution.

RELATIVE HUMIDITY
“How is humidity measured?” you may wonder. This is where the term Relative Humidity (RH) comes into play. RH refers to the amount of water vapor in the air, expressed as a percentage of the maximum amount the air could hold at the same temperature. When warm air is cooled, the RH goes up. When cold air is heated, the RH lowers.

Cellulose, as the raw material of paper, is hygroscopic. This means it responds to changes in relative humidity by expanding when humidity levels are high and contracting when they are low. Paper has an attraction to water since it contains water on its surface and within its chemical structure. Surface water is eliminated first when RH is low. Once this supply is exhausted, structural water is given up.

This action caused by low RH results in shrinkage, cracking and desiccation of paper and adhesives and flaking of photographic emulsions. Desiccated paper is more easily torn when handled. It must be noted, that structural water, unlike the surface kind, cannot be regained. Other damages caused by low RH include stiffening and flaking of adhesives and emulsions on photographs.

High humidity on the other hand, can lead to insect activity, delamination, bleeding of watercolors,distortions, adhesions of coated paper, ink transfer and mold growth. Mold stains and weakens paper and leather.

Similarly, to temperature, fluctuations in RH can also lead to damage. However, the damage occurs when various parts of an object respond at different rates. Composite objects such as books, photographs and paper adhered to stretchers, cloth or board, as well as material with partial constraints like repairs and mounts, among other objects are easy targets for fluctuating RH damage.

The Canadian Conservation Institute’s (CCI) Damage Caused by Incorrect Temperature and RH guide notes that the swelling and contraction of paper in response to humidity does not cause damage in and of itself. As previously mentioned, it is the fluctuation in addition to the presence of a secondary or tertiary incompatible material that leads to trouble.

SO, WHAT’S MY RELATIVE HUMIDITY GOAL?

The 2011 Specification for Environmental Condition for Cultural Collection released by the British Standards Institute describes that below 25% RH, the risk of physical damage increases rapidly and at 75% RH and above, the dimensional change due to each 5% rise in RH increases exponentially.

Now that that’s out of the way…
The recommended RH lies between 45-65% With an allowed fluctuation of ±5%. The safe RH boundary usually cited to prevent mold growth is below 65%, although 70% has also been cited. Photographic materials require an RH between 30% and 40%.

HOW TO PROTECT YOUR BOOKS AND PAPERS FROM HUMIDITY
Similarly to protect from extreme temperatures, storing your objects in an archival box, folder or envelope will provide a barrier from humidity fluctuations. If box making or purchasing archival boxes are not feasible, consider interleaving book pages with acid free tissue to slow down acid degradation which is what causes paper to be fragile, yellow and crack easily.

Should I be freaking out about the fluctuations in RH in my stacks?
The short answer is no.

Although the goal is to keep a steady RH between 45-65%, fluctuations are inevitable due to the change of seasons or a lack of means to invest in a sophisticated HVAC system.

In Stefan Michalski’s Agent of Deterioration: Incorrect Relative Humidity “proofed” fluctuation is discussed. This is the largest fluctuation that the object has ever witnessed. The “proof” is in the pudding. What this means, is that any fluctuation smaller than the proofed will cause less damage than what has been caused in the past (if any at all). The good news is that even minor changes in spaces where fluctuations have occurred, will reduce the risk of damage to your collection.

Resources:

British Standards Institute (BSI). 2011. PAS 198:2011. Specification for environmental conditions for cultural collections.

Fahey, M.2002. The Care and Preservation of Documents and Works of Art on Paper. Michigan: The Henry Ford.

Fahey, M.2016. The Care and Preservation of Archival Materials. Michigan: The Henry Ford.

Grattan, D., and Michalski, S. 2015. Environmental Guidelines for Museums. Ontario:Canadian Conservation Institute (CC).

Library of Congress. The Deterioration and Preservation of Paper: Some Essential Facts.

Michalski, S. 2016. Agent of Deterioration: Incorrect Relative Humidity. Ontario: Canadian Conservation Institute (CC).

Michalski, S. 2016. Agent of Deterioration: Incorrect Temperature. Ontario: Canadian Conservation Institute (CC)

National Information Standards Organization (NISO).1995. NISO TR01-1995. Environmental Guidelines for the Storage of Paper Records.

National Parks Service (NPS). 2003. Part I: Museum Collections. Appendix J: Curatorial Care of Paper Objects.

National Parks Service (NPS). 2016. Part I: Museum Collections. Ch. 4: Museum Collections Environment.

Northeast Document Conservation Center (NEDCC). The Environment. 2.1 Temperature, Relative Humidity, Light, and Air Quality: Basic Guidelines for Preservation.

In honor of Preservation Week, our Special Collections Conservator, Natalie Granados is sharing some of the work she does to ensure that all of our collections are getting the care and maintenance they deserve.

Temperature: What Is Damaging Your Collections?

Written by Natalie Granados (@natartlie). Special Collections Conservator – UConn Library.

On this post we’ll discuss temperature and how it affects your collection material. Knowing what causes common problems in books and paper will help you protect your treasures. Join me in this series covering common damages to paper and books such as handling, temperature, humidity, pests and pollution.

LET’S START WITH SOME SAD FACTS:It must be noted that the quality of the paper itself can be one of its causes of deterioration. Inherently acidic pulp, acidic inks, bleaching and unstable sizing all speed up degradation. Paper that presents these characteristics benefits from cold storage to slow down the chemical process causing the decay.

CHEMICAL DAMAGE
The unseen changes within paper is what concerns conservators. Hydrolysis and oxidation being the big bad wolves in this scenario.

Hydrolysis is a chemical reaction between a substance and water, resulting in the breakdown of the original substance and the formation of one or more new substances. In paper, acid hydrolysis is a continuous process that decreases flexibility and increases the susceptibility to damage of the object. Because the activity itself creates acid, the damage will increase as the process progresses.

Oxidation is a reaction between a substance and oxygen, resulting in physical breakdown. It can be caused by light, heat or pollutants and it leads to discoloration (yellowing) of paper.

TEMPERATURE
Library and archive materials respond to temperature by expanding in heat and contracting in cold. Heat accelerates damage, causes permanent distortion, cracking, change of sheen and melting of adhesives and paint. In addition, insects reproduce faster and eat more at higher temperatures.

Alas, very cold temperatures are not any better. These can make paper liable to break easily, crack or flake. Extreme variations can also be a problem. Extremes that occur faster than the paper’s rate of adjustment can lead to cockling, wrinkling, and planar distortions as well as cracking of emulsions on photograph.

GOT IT. NOW WHAT TEMPERATURE PARAMETERS SHOULD I BE LOOKING AT?
Glad you asked, the recommended temperature for spaces where human comfort is a factor is between 60-77°F. For storage of paper records with only occasional retrieval,a constant temperature within the range from deep freeze to about 64°F would be suitable as per the National Information Standards Organization (NISO) Environmental Guidelines for The Storage of Paper Records. For film and color photographic material, a suggested temperature of 35°F or below has been stated.

In honor of Preservation Week, our Special Collections Conservator, Natalie Granados is sharing some of the work she does to ensure that all of our collections are getting the care and maintenance they deserve.

Handling Books and Papers

Written by Natalie Granados (@natartlie). Special Collections Conservator – UConn Library.

Improper handling and incorrect storage can have negative effects on the lifespan of your books and papers. In addition, damage is often cumulative and can go unnoticed till it’s too late. Good handling practices will reduce common damages as well as the need for a conservator. The downloadable guide (Collection Handling: Quick Tips) that accompanies this post provides tips to help you care for collections and ensure their survival for future generation’s use. Below you’ll also find general information on the books and flat materials and how they are affected by improper handling. Like the cultural superhero that you are though, you know that handling everything with care even if it doesn’t look fragile is the way to go.

Books
Keep in mind that books are subject to structural stress. Few bindings can open completely flat. For this reason, they should always be supported (with book cradles, for example) when open. When opening new or newly bound books, try not to open them from the center, as this can break the structure. Start from the front and then back, and open them gradually, section by section till you reach the middle. This slowly eases them open and flexes the new structure gently.

Flat Material
Paper is highly susceptible to physical damage such as creasing or tearing. In addition, if graphite, charcoal, pastel and/or watercolor pieces are abraded, the damage is permanent. Consider storing and moving this type of material in an enclosure or over heavy-weight paper or board.

Speaking of Enclosures
Besides protecting from temperature and relative humidity variations, light, pollutants and insects, enclosures (boxes, portfolios, sleeves and envelopes) can protect valuable and fragile material from accidents and incorrect transportation. Since objects are most vulnerable to damage when they are being moved, planned movements and proper housing will lower the chances of accidents. Make sure you have a clear route and a place to set your items ahead of time. The photos are an enclosure made to ship some materials from our Alternative Press Collection on loan.

Clean Hands and The Use of Gloves
Sometimes clean hands aren’t quite as clean as we may think. You’ll notice “Please wash your hands” signs in cultural institutions providing access to collections, but what is often not mentioned are lotions, creams, and alcohol-based hand sanitizing gels. These leave behind oils that attract dirt and dust and can stain material. Make sure to wash any residue from lotions or gels off your hands to avoid causing damage to collections.

Bear with me here while we dispel the “white glove” myth. Cotton gloves are not our buddies all the time and have fallen out of favor in the conservation community. These types of gloves are cumbersome and ill-fitting, making proper handling difficult. In addition, cotton gloves have small hairs that can catch on edges and expand tears. Finally, cotton as an absorbent material, can pick up dirt and dust and deposit it on your collections. Exceptions are made when handling photographic material, as the oil on your fingers can damage the emulsion. For everything else, handling material with clean, lotion-free hands is preferable.

Stay tuned for her next post – Temperature: What Is Damaging Your Collections?