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Archival Leaflets - Encapsulation


Mark Shenise, Associate Archivist



Encapsulation is the preservation process that provides greater support to a document that is in fragile condition.  It is a process that allows a fragile document to be sealed between two sheets of polyester film for protective viewing and ease of handling. The final result is called a capsule. Contrary to prior archival wisdom of ages past encapsulation does not slow down the rate of deterioration of a document. The reverse is true. Without proper preparation to the document before it is encapsulated the rate of deterioration is actually faster than if stored under standard archival conditions. This, however, does not diminish the role and value of encapsulation for rare and fragile documents that have intrinsic historical value.

Encapsulation is primarily used for single sheet documents. If there is more than one sheet to be encapsulated within a given document it stands to reason that each sheet should be encapsulated separately from the others.

It is important to know that there are many different types of polyester film on the commercial market. Let the buyer beware! Only one type of polyester film is considered stable enough to be archival. There are two companies who manufacture this type of film. One product is called Mylar? Type D (manufactured by the DuPont Corporation) which is commonly referred to as Mylar. The other product is called Melinex® 516 (manufactured by ICI Americas). The sheets come in pre-cut sizes or rolls. These sheets are available in 3, 4, and 5 mil thickness. The weight and size of the document determines the thickness of the sheet. Most smaller documents will be encapsulated in 3 mil sheets. Medium size documents should be encapsulated in 4 mil sheets and larger and/or oversized documents should be encapsulated in 5 mil sheets. The greater the thickness the more expensive the sheet.

Another important fact to remember is that only one type of double-sided tape is considered archival and safe for encapsulation. Use only 3M Scotch Brand double-sided tape no. 415®**. This tape comes in both 1/4 and 1/2 widths. The latter width is used primarily with larger and heavier documents. Do not use any other type of double-sided tape since they are not archival and can cause irreversible damage to your document!


 This is the most important question the archivist/church historian needs to ask at the onset of any potential encapsulation project. Encapsulation can be a very expensive endeavor, especially if there are a number of fragile documents in need of special storage. This method of preservation is very tempting but can ruin a limited budget if the archivist/church historian is not careful. If the document itself does not have intrinsic value and the information within has only historical value, then a photocopy of the document on acid-free paper may be a better cost effective measure.

Here are some sample questions that you might want to ask yourself when creating a criteria for encapsulation.

    Does the document need greater physical support for viewing and storage?

    Can the document be handled without much fear of tearing or breaking?

    Does the document need additional protection from such hazards as extreme heat, moisture, light, and air pollution? It should be noted that certain inks will still fade despite encapsulation.

It must be remembered that encapsulation is not considered a permanent enclosure. This method of preservation can be reversed if need be by simply cutting the film next to the adhesive to release the document.

Another reason to consider encapsulation is that of transportation. If you have a fragile document that is to be transported and/or removed with any type of frequency it would be advisable for the archivist/church historian to purchase self-sealing Mylar® L-Velopes®. These envelopes are permanently sealed on two sides which allows a document to be accessed from the two other open sides. The advantage for this style of encapsulation is that you do not destroy the capsule in order to gain access to the document in question. Three sided envelopes are not recommended since you increase the danger of tearing your document upon insertion or removal from the capsule. Homemade envelopes can be made if your budget does not allow for the purchase of pre-manufactured envelopes.


 Here are a few suggestions in deciding what record types can or cannot be encapsulated.


    * Charcoal drawings

    * Pastel drawings

    * Thickly applied water colors

    * Records with small tears on the borders where information is lacking

    * Some pencil based writings


    * Fragile documents with a long tear(s) in them

    * Photographs

    * Certificates

    * Handbills

    * Broadsides

    * Small textiles such as bookmarks, swatches, etc.

    * Other paper based records

If you are in doubt whether the document’s medium will withstand the encapsulation process and not destroy the information contained therein, here is a simple test. Take a very small piece of polyester and gently rub it on an area of the medium in question where loss of information is not important to the historical content of the document. If any residue comes up with the polyester this is a clear indication that encapsulating this specific document should not be done.

Advance forms of preparation for a document that is to be encapsulated can be handled in the following ways. If the document is not deacidified prior to encapsulation an identification tag should be included within the capsule stating this fact. The label should read non-deacidified which is typed on an acid-free (buffered) piece of paper and placed in the lower right hand corner of the capsule. If the document only has information on the front side, cut a piece of acid-free paper the same size of the document and place this sheet on the back side of the document before encapsulating. Another variation of this method is used when information is also included on the back side (verso) of a document. Photocopy the back side of the document on acid-free paper and place the photocopy over the original. This method can actually slow down the rate of deterioration of the document within the capsule!


 Here is a list of basic tools you will need to complete the encapsulation process:

    * A large flat surface

    * Polyester film*

    * Double coated adhesive tape**

    * Cotton gloves

    * A soft lint-free cloth. Cheesecloth is an example.

    * Weight(s). You can buy these or make your own. If you make your own make sure that it is encased in a soft lint-free cloth. Base items to be used could include a half brick, book, fishing weights, old printing plates, etc.

    * Cutting tool such as a utility knife (preferably an X-Acto® knife), razor blade, scissors, or paper cutter. If using a utility knife you will need a straight edge for guidance. Standard edges include a T-Square or metal ruler. If you use a utility knife you will also need a cutting board.

    * Pressure tool such as a brayer (a rubber roller with a handle) or a squeegee.

Optional tools (Highly recommended)

    * Alignment grid. This rubberized mat will help you to measure, center, and hold your capsule in place as you create it. It also doubles as a cutting board.

    * Small stainless-steel spatula. Not the kind you cook with but a narrow tool with the ends flattened.

    * Bone Folder. This doubles as a folding tool for polyester film. It usually comes in an 8" tapered body with rounded edges.

    * Two inch plastic putty knife. Can be used in place of a Bone Folder.

    * Nail clipper.

   An encapsulation kit with the appropriate tools can be obtained through University Products (1-800-532-9281).  This is a very good way to start your encapsulation program.


   1. Wipe the large flat surface clean with a dry lint-free cloth. Do not use a chemical cleaner!

   2. Put on your cotton gloves.

   3. Measure the document that is to be encapsulated.

   4. Cut two sheets of polyester film that will create a 1 or 1.25 inch border on all sides of the document. For example: A 3 x 5 inch record should be encapsulated between two sheets of film measuring 5 or 5.25 x 7 or 7.25 inches.

   5. Place a sheet of polyester film on a clean, flat surface (with or without a grid).

   6. Wipe the sheet of polyester film with a lint-free cloth. This cleans the surface and creates static electricity which helps to hold the document in place. Note that the polyester film scratches easily and attracts dirt. It is imperative that the film is wiped clean!

   7. Center the backing sheet (acid-free paper cut to size) on the film if you are using this method. Then place the document over the backing sheet. If you are not using the backing sheet method center the document itself on the film.

   8. Center and place the weight on the document.

   9. Apply the exposed sticky side of the adhesive tape to the film in a parallel manner from 1/8 to a 1/4 inch in from the entire edge of the film. Butt up two of the four ends of the tape so they touch each other but do not overlap. Make sure your end cuts are square. At two opposing corners leave a small gap approximately a sixteenth of an inch to allow air to escape when applying the second sheet of film. When you are done it should look like a picture frame with the exception of the two offset small gaps in two of the corners.

  10. OPTION If you are storing the capsule in a vertical position rather than horizontally it is a good idea to cut two thin strips of polyester film the same size as the length of the document. After cleaning the strips place them between the document itself and the adhesive tape. This will prevent the document from shifting within the capsule when being stored and touching the adhesive. Touching the adhesive can ruin the document if you ever plan to take it out of the capsule for future preservation work or display purposes.

  11. Wipe the second sheet of polyester film.

  12. Remove the weight from the document.

  13. Center the second piece of polyester film over the first with the cleaned side facing down.

  14. Center and place the weight back on top of the second sheet of polyester film.

  15. Gently roll the brayer or lightly pull your squeegee over the top of the capsule.

  16. Carefully lift one corner of the top sheet of polyester film. A small spatula or other similar type of tool can aid you in this step. Slowly peel the brown protective cover from your adhesive tape. Continue the same for the next three sides.

  17. Take the weight off of the capsule.

  18. Remove the air from between the two sheets of polyester film by sliding the squeegee or brayer across the top of the capsule in the direction of the small opening in the adhesive tape at the one corner. Not only will this push unwanted air out of the capsule but also seals the capsule as well. Make sure that the adhesive is optimally working by rubbing a Bone Folder or 2 inch plastic putty knife over the top of the polyester film where it meets the adhesive. Your gloved finger will work just as well if you do not have a Bone Folder.

  19. If needed trim the edges of the capsule with a pair of scissors or a hobby knife in conjunction with a straight edge (metal ruler) so that neither polyester sheet overlaps the other.

  20. Trim the corners of your capsule with scissors or a nail clipper so they have a nice round edge. This will prevent the capsule from damaging other records when used by a patron.

  21. Wipe both the top and bottom sheets of the capsule to remove any lingering fingerprints or impurities.

   The local church/conference archivist should remember the old axiom that practice makes perfect. The more you encapsulate the better your end result will be. You will be surprised how quickly your skills will grow with each subsequent encapsulation.


 Ritzenthaler, Mary Lynn. Preserving Archives and Manuscripts. SAA Archival Fundamentals Series. Chicago: Society of American Archivists, 1993.