October is American Archives Month—How to make a Humidification Chamber

Humidification is the process of introducing moisture into paper by placing the document inside an enclosed area with a water source.  This is often done for tightly rolled documents such as large maps, posters, or large pictures.  Water vapor enters the fibers of the document, allowing them to relax.  Often the document may then be opened safely, after which it can be pressed and dried to keep it flat.

A conservator is a professional whose primary occupation is the practice of conservation and who, through specialized education, knowledge, training and experience, formulates and implements all the activities of conservation in accordance with an ethical code such as the American Institute for Conservation of Historic and Artistic Works (AIC) Code of Ethics and Guidelines for Practice.

Humidification is relatively safe, but there is always some risk when documents are exposed to water.

Items that should only be treated by professional conservators are:

  • Rare and valuable documents.
  • Non-paper documents such as parchment and vellum.
  • Photographs.
  • Documents that are heavily soiled.
  • Documents that show previous mold growth
  • Documents with water soluble inks or paints as they may smear or bleed into the paper.

For help finding a conservator, contact the American Institute for Conservation at 202-452-9545 or visit their website at www.conservation-us.org.

Moving on to the fun stuff!  What supplies do I need to make a Humidification Chamber?

Supply list:

  • Plastic container with a tight-fitting lid, they come in different sizes and shapes.  Select one made of plastic with no ventilation holes.  Remember to choose a container which works best for the documents you want to flatten.  Examples below:

container_1 container_2

  • 2-3 bath towels.
  • Water pitcher.
  • 4 freezer containers.  You can find these at any grocery store, Walmart or Target for less than $4.00.
  • Warm water.
  • “Egg Crate” light panel.  These are plastic grids with holes in them.  The documents will rest on this panel so it should have a small grid, approximately ½”, to give even support.  The panel should be at least 3/8” thick, to prevent the document from touching the water filled containers beneath it.  Cut the panel to fit on the lip of the container.  You may need to cut the panel to fit in the container. Use caution when cutting because the plastic is brittle, and bits may fly about as it is cut.  Wear protective eye gear when cutting the panel.  Another option is asking hardware store staff to trim it for you.

eggcrate_1 eggcrate_2










  • Blotting paper—purchase online at suppliers such as universityproducts.com or Gaylord.com.
  • Paper for signage.  Use this wording for the Sign: Humidification in Process.

Pre-humidification steps:

  • Unfold or unroll the document before humidifying, if that can be done without damaging it.
  • Remove staples and paper clips.  Metal fasteners can rust in humid conditions.

Humidification procedure:

  • Step 1—Fold towels and place at the bottom of the container.
  • Step 2- Place 4 freezer containers of equal size on top of the towels
  • Step3- Pour warm water into the freezer containers.
  • Step4-Place egg crate panel on the lip of the container. It should fit snuggly, raised a few inches above the freezer containers to avoid their contact with document.
  • Step 5- Cover the container and wait patiently for 4-8 hours.  Check the progress of the document every 15-20 minutes.  If you have to open the container, do not leave the lid off for long, or the humid air will escape, and this will prolong the humidification process.
  • Step 6- Remove document from container, it will unroll on its own.
  • Step 7- Lay the document flat on blotting paper.  Make sure blotting paper covers top and bottom of the document you are drying.  Use a book to provide even pressure while the document is drying.  Leave on blotter paper for a minimum of 12 hours.
  • Final step-Remove document from blotter stack.  You are finished with humidifying your document.

For more information about the Archives or to make an appointment to view archival materials, contact Mellisa DeThorne, Special Collections Assistant, at 210-567-2470 or dethorne@uthscsa.edu.

Happy American Archives Month, All!

Mellisa DeThorne, Keeper of precious things


Information Courtesy of: