A University Products How-To Tip: Encapsulation

One of the safest, most effective means of protecting a document from harm is through encapsulation. Encapsulation allows you to view and handle a document without exposing it to hazardous elements. The process involves the positioning of a flat document between two pieces of polyester film that are then sealed on all sides.

Clear Plastic Films
There are a variety of clear plastic films on the market. Some contain plasticizers or surface coatings that are inappropriate for encapsulation. They can and will react with the items they come in contact with, doing more harm than good. If you are planning to encapsulate, be certain you are using inert polyester. The material you choose should be free of plasticizers, or surface coatings of any kind.

Sealing
Sealing the polyester also involves specific methods and materials. Heat sealing and ultrasonic welding equipment is available for adhesive-free sealing of polyester. However, the price tag for this type of equipment may be prohibitive for the average collector. The alternative is to use a double sided pressure sensitive tape. The tape should feature a stable acrylic adhesive such as 3M’s No. 415 Polyester Transparent Tape.

Pre-Formed Encapsulation
An alternative to buying expensive equipment or using adhesive tape is to purchase pre-formed encapsulation units. They are available in sizes and styles that will accommodate items of just about any size. If you plan on encapsulating a small quantity of items, this may be the most economical and time saving approach. Should you choose this route, be sure, once again, that the encapsulation units you purchase are made from an inert polyester.

Research has shown that encapsulation can increase the rate of deterioration of an acidic document. A qualified conservator can determine if a document is acidic and also perform a deacidification treatment if it is required.

Besides the protection factor encapsulation provides, static electricity inherent in polyester film will hold a document in place. Worn and fragile documents benefit greatly from this static charge since it helps hold torn pages together. The downside is the same charge will attract some mediums, such as charcoal or pastels, away from the document. A qualified conservator can determine if a particular document should or should not be encapsulated.

Once an item is determined to be safe for encapsulation, and the procedure is complete, your document is safe from dirt, pollution and fingerprints. Encapsulation will not, however, protect your autographed document from the hazards of ultraviolet light, and temperature and humidity extremes. Your encapsulated document should be stored out of the light in a climate controlled environment. Ideally, it should be stored flat in an archival quality box.

Conservation Photo Feature – Recent conservation project at the San Diego Museum of Man

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Removing mold from a human mummy at the San Diego Museum of Man

Unfortunately, the chiller in our HVAC system broke down, resulting in humidity increases in some of our exhibit galleries. As a result, mold began to appear on one of our naturally preserved human mummies. We removed the mummy from the gallery, and kept it sealed in an airtight storage cabinet with dessicant in order to dry out the mold. We then vacuumed the mold off of the mummy. Our chiller has since been replaced, and the mummy is back on display in the gallery, and it is doing fine!

Photo and story courtesy of San Diego Museum of Man (SDMoM), the only anthropology and archaeology museum in San Diego County. SDMoM is located in Balboa Park in the historic 1915 California Building with its iconic California Tower. SDMoM has outstanding cultural (ethnographic) collections and renowned physical anthropology collections. It features five permanent exhibitions, including Ancient Egypt; Kumeyaay: Native Californians; Footsteps Through Time: Four Million Years of Human Evolution; Maya: Heart of Sky, Heart of Earth; and Discover Egypt. SDMoM also offers changing special exhibits featuring artifacts from it’s own collections and from around the world.

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A University Products How-To Tip: Temperature & Humidity

Temperature and Humidity
Besides light, there are additional environmental concerns, such as temperature and humidity, that can  adversely affect a collection. For every 18 degree F (10 C) increase in temperature, it is estimated that chemical reactions in paper double. Relative humidity is a measure of the capacity of air to hold water. This amount varies as temperatures increase or decrease. Paper and other porous materials either absorb or lose moisture as temperature and humidity levels vary. This action causes shrinking, stretching, and the eventual breakdown of structural fibers, while contributing to formation of acids. The effect is similar to the cracking, splitting, and weaknesses that result when an outdoor wooden deck is left unprotected, though on a microscopic level.

While the ideal temperature and relative humidity levels for proper storage of paper are yet to be agreed upon, consistency seems to be the key factor. The best advice is to treat your collection like one of the family. Hot attics and damp basements make poor living quarters; they also make poor storage facilities. Even a closet that abuts an outside wall may be exposed to a large range of temperature and RH fluctuations over the course of a year.

Monitoring
Maxant HygrothermographWhen properly monitored, the combination of heating and air conditioning equipment, as well as humidifiers and dehumidifiers, allows the maintenance of a stable climate. There are also a variety of tools (with a variety of price levels and degrees of sophistication) that can assist in the monitoring. When fluctuations can be controlled, acid formation and mechanical degradation can be slowed significantly.

Desiccants
In the absence of expensive equipment, RH levels can be controlled and stabilized with the help of desiccants such as Silica Gel. Silica Gel is a porous granular, chemically inert amorphous silica that can absorb 40% to 50 % of its own weight in water. The material comes in several forms including reusable canisters, beads, sheets, and packets. Because it can become fully saturated, Silica Gel must be monitored and reconditioned when saturation occurs. One form of Silica Gel changes from orange to a pale pink to indicate it has reached the saturation level. Again, a proper schedule of monitoring your collection should be maintained to achieve a stable environment.

Having addressed the problems associated with fluctuations in temperature and humidity, it is equally important to address the more obvious problems which occur with constant extremes. The combination of high temperature and relative humidity promotes mold growth and encourages insect infestation, whereas a cold and dry environment leads to embrittlement. As you may have guessed, neither scenario is going to improve the condition of your collection.

Acceptable temperatures in your storage area should remain lower than 68 degrees F, with relative humidity between 30 and 50%.  Fluctuations should not exceed +/- 5 degrees F in temperature, and  +/- 3% relative humidity within a 24 hour period.

Most museums and libraries strive to achieve the ideal conditions described above, but they may fall under the same restraints that you and I are likely to come across. Lack of time, expertise, and money can prevent us from achieving ultimate conditions. In addition, each of our individual geographic locations can present problems unique to that area. All we can do is strive for improvement.