Introduction to Preservation


Preservation is at the core of what we do at the Houston Metropolitan Research Center. Each spring, we take the opportunity to talk about what this means to us during  Preservation Week,  an annual observance by the American Library Association highlighting the importance of preserving materials in collecting institutions. While Preservation Week centers on professional archives and museums, it’s also about helping people preserve their own memories for themselves, their family, and their community.

Check out the Houston Public Library Instagram Stories to follow the Houston Metropolitan Research Center’s Preservation Takeover. We will take you behind the scenes with HMRC’s Preservation Librarian, sharing what preservation looks like in the archives, and offering tips for those at home.

Below are some tips for preserving your own materials and further resources.

Preservation versus Conservation

Preservation aims to prolong the life of objects. The goal is to minimize deterioration. Preservation is when you take measures that prevent damage or reduce the potential for damage or loss. It works to modify conditions that foster deterioration on a collection as a whole.  Conservation, on the other hand, is when you repair damage that has already occurred. It concerns the treatment of individual objects though stabilization or restoration.


Environment concerns the air quality, humidity, temperature, ventilation, light, dampness, and heat.

9 Agents of Deterioration

  • Incorrect Temperature
    • High temperatures cause chemical deterioration
    • Low temperatures causes stress to flexible structures
    • Fluctuating temperatures cause delaminating and cracking
    • Standard temperature is 70°F, +/- 2 degrees
  • Incorrect Relative Humidity (RH)
    • As the temperature gets cooler, the humidity rises
    • Low RH results in drying and cracking; High RH results in mold
    • Rapidly fluctuating RH results in structural damage
    • Ideal RH is 50%, +/- 5%
    • Reference standard for paper is 68°F. This results in a useful life of 100 years.
      • 95°F and 80% RH results in a useful life of 3 years.
      • 50°F and 40% RH results in a useful life of 1200 years.
  • Light/Radiation
    • Radiation from light waves fades and embrittles sensitive material.
      • Both UV light and visible light damages materials.
      • Damage is cumulative and irreversible; damage is hard to see at first
    • Light wave energy triggers destructive chemical reactions.
  • Direct Physical Force
    • Direct physical force, such as tearing or dropping a book, causes immediate visible damage.
  • Pests
    • Many different bugs like to eat or live in materials.
    • Watch out for moths, silverfish, termites, and cockroaches.
  • Contaminants
    • Damage from air pollution is difficult to see in the short-term, but very serious over long term.
      • Watch out for hair, skin cells, soot, fibers, pollen, plaster, gases, and chemicals.
    • Sometimes items will deteriorate over time because of what is in them or what has been added during the manufacturing process and any actions only help minimize the damage and prolong its life. [Inherent Vice]
      • Examples: Acidic paper, leather covers, glue, self adhesive tape, and ink.
  • Fire
    • Heat and smoke cause accelerated aging.
    • Heat melts different materials.
    • Look for insects, mold, and vermin in the water damaged areas from dousing the flames with water.
    • Heat and smoke cause fading, scorching, scarring and staining.
  • Water
    • Floods, leaky roofs, or slow drips from pipes damage collections.  Damage includes:
      • Bleeding; Molding and rotting; Lifting of veneers; Separation of emulsion layers
  • Thieves, Vandals, Displacers
    • The negative actions of others who are not concerned with preservation of your materials often cause damage.

Handling Tips


  • Shelve by size, upright, supported by bookends if needed.
  • Support books when removing them from shelves and when carrying them.
    • Don’t pull on the headcap (top of the spine) of a book to remove it from the shelf.
    • Push in the books on either side to remove the book in the middle.
  • Store large volumes flat.
  • Always store books spine down when packing books away. Stored spine up will allow gravity to pull the textblock away from the spine of the book.
  • Don’t fold over corners or use post-its; don’t leave it open, face down, or stacked with others.


  • Store documents upright in file folders and boxes or flat.
  • Don’t use envelopes because envelopes cause damage when inserting and removing items.
  • Ensure that the enclosures you purchase – boxes and folders – are acid-free, lignin-free, and buffered.
    • Acid-free folders have a pH of 7.0 or higher; lignin-free folders have lignin content of 1% or less; buffered folders have a basic pH to off-set the acid content in the document.
    • Lignin, found in the bark of wood, causes paper to darken while raising the acid level.
  • Ensure the documents are exposed to as little light as possible while in storage.
  • Remove materials such as cardboard, rubber bands, and paper clips.


  • Wear protective gloves when handling photographs.
  • House photos in protective enclosures to keep out gritty dirt and dust which can scratch and then in acid-free boxes. Avoid using pressure-sensitive tapes and rubber cement.
  • Remove materials such as cardboard, rubber bands, and paper clips.
  • Suitable storage materials are made of plastic or paper. Paper enclosures should be acid-free; plastic enclosures should be made of uncoated polyester film, uncoated cellulose triacetate, polyethylene, and polypropylene. Note: Photographic emulsions may stick to the slick plastic surfaces of these storage materials at high relative humidity (rH). Plastic enclosures must not be used for glass plate, nitrate, or acetate-based negatives.

Oversized Items

  • Store flat where possible, not folded or rolled.


  • Interleave the pages with an unbuffered acid-free paper.
  • Isolate or encapsulate problem materials, such as sticky or acidic items.
  • Support the entire leaf when turning the pages, particularly if weighed down by the materials attached.
  • Don’t force it to lay open flat.

Suggestions for Display

  • Interior rooms are more stable than those with outside walls.
  • Don’t store or display materials above or immediately adjacent to heat vents, radiators, and fireplaces.
  • Don’t hang framed works of art of any value on outside walls; use spacers between the frame and the wall.
  • Make a copy and put it out for viewing while storing the original.

Useful Preservation Websites

Links to Vendors of Archival Supplies

Library of Congress Personal Archiving

Preservation Tips

American Institute for Conservation  

Library of Congress Preservation – Collections Care

Northeast Document Conservation Center

Preservation 101 handout PDF available here.

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