--- title: Archival Terminology Explained description: Understand key archival terminology, including acid-free, deacidification, and archival polyester, to better preserve and protect cultural and historical materials. image: https://info.gaylord.com/hubfs/Blog_AK/ArchivalTerminology.png --- - [SHOP PRESERVATION](https://www.gaylord.com/c/Preservation) - [SHOP EXHIBIT](https://www.gaylord.com/c/Exhibit-and-Display) [![Gaylord Archival Resource Center](https://info.gaylord.com/hs-fs/hubfs/GALogo-Transparent-3.png?width=65&height=79&name=GALogo-Transparent-3.png "Gaylord Archival Resource Center")](https://info.gaylord.com/resources/home) Search toggle - [PRESERVATION](https://info.gaylord.com/resources/tag/preservation) PRESERVATION - [ARCHIVAL BASICS](https://info.gaylord.com/resources/tag/archival-basics) - [COLLECTIBLES](https://info.gaylord.com/resources/tag/collectibles-artifacts) - [BOOKS](https://info.gaylord.com/resources/tag/books) - [DOCUMENTS](https://info.gaylord.com/resources/tag/documents) - [GARMENTS & TEXTILES](https://info.gaylord.com/resources/tag/garments-textiles) - [MEDIA](https://info.gaylord.com/resource-center/tag/media) - [PHOTOS](https://info.gaylord.com/resources/tag/photos) - [EXHIBIT](https://info.gaylord.com/resources/tag/exhibit) EXHIBIT - [EXHIBIT CASES](https://info.gaylord.com/resources/tag/exhibit-cases) - [EXHIBIT PLANNING](https://info.gaylord.com/resources/tag/exhibit-planning) - [VISITOR ENGAGEMENT](https://info.gaylord.com/resources/tag/visitor-engagement) - [ENVIRONMENTAL CONTROL](https://info.gaylord.com/resources/tag/environmental-control) ENVIRONMENTAL CONTROL - [EMERGENCY PLANNING](https://info.gaylord.com/resources/tag/emergency-planning) - [MONITORING](https://info.gaylord.com/resources/tag/monitoring) - [SILICA GEL](https://info.gaylord.com/resources/tag/silica-gel) - [MUSEUM STORAGE](https://info.gaylord.com/resources/tag/museum-storage) - [WEBINARS](https://info.gaylord.com/resources/webinar-archive) [![Gaylord Archival Resource Center](https://info.gaylord.com/hs-fs/hubfs/GALogo-Transparent-3.png?width=65&height=79&name=GALogo-Transparent-3.png "Gaylord Archival Resource Center")](https://info.gaylord.com/resources/home) - [PRESERVATION](https://info.gaylord.com/resources/tag/preservation) PRESERVATION - [ARCHIVAL BASICS](https://info.gaylord.com/resources/tag/archival-basics) - [COLLECTIBLES](https://info.gaylord.com/resources/tag/collectibles-artifacts) - [BOOKS](https://info.gaylord.com/resources/tag/books) - [DOCUMENTS](https://info.gaylord.com/resources/tag/documents) - [GARMENTS & TEXTILES](https://info.gaylord.com/resources/tag/garments-textiles) - [MEDIA](https://info.gaylord.com/resource-center/tag/media) - [PHOTOS](https://info.gaylord.com/resources/tag/photos) - [EXHIBIT](https://info.gaylord.com/resources/tag/exhibit) EXHIBIT - [EXHIBIT CASES](https://info.gaylord.com/resources/tag/exhibit-cases) - [EXHIBIT PLANNING](https://info.gaylord.com/resources/tag/exhibit-planning) - [VISITOR ENGAGEMENT](https://info.gaylord.com/resources/tag/visitor-engagement) - [ENVIRONMENTAL CONTROL](https://info.gaylord.com/resources/tag/environmental-control) ENVIRONMENTAL CONTROL - [EMERGENCY PLANNING](https://info.gaylord.com/resources/tag/emergency-planning) - [MONITORING](https://info.gaylord.com/resources/tag/monitoring) - [SILICA GEL](https://info.gaylord.com/resources/tag/silica-gel) - [MUSEUM STORAGE](https://info.gaylord.com/resources/tag/museum-storage) - [WEBINARS](https://info.gaylord.com/resources/webinar-archive) Search toggle [![Gaylord Archival Resource Center](https://info.gaylord.com/hs-fs/hubfs/GALogo-Transparent-3.png?width=65&height=79&name=GALogo-Transparent-3.png "Gaylord Archival Resource Center")](https://info.gaylord.com/resources/home) - [PRESERVATION](https://info.gaylord.com/resources/tag/preservation) PRESERVATION - [ARCHIVAL BASICS](https://info.gaylord.com/resources/tag/archival-basics) - [COLLECTIBLES](https://info.gaylord.com/resources/tag/collectibles-artifacts) - [BOOKS](https://info.gaylord.com/resources/tag/books) - [DOCUMENTS](https://info.gaylord.com/resources/tag/documents) - [GARMENTS & TEXTILES](https://info.gaylord.com/resources/tag/garments-textiles) - [MEDIA](https://info.gaylord.com/resource-center/tag/media) - [PHOTOS](https://info.gaylord.com/resources/tag/photos) - [EXHIBIT](https://info.gaylord.com/resources/tag/exhibit) EXHIBIT - [EXHIBIT CASES](https://info.gaylord.com/resources/tag/exhibit-cases) - [EXHIBIT PLANNING](https://info.gaylord.com/resources/tag/exhibit-planning) - [VISITOR ENGAGEMENT](https://info.gaylord.com/resources/tag/visitor-engagement) - [ENVIRONMENTAL CONTROL](https://info.gaylord.com/resources/tag/environmental-control) ENVIRONMENTAL CONTROL - [EMERGENCY PLANNING](https://info.gaylord.com/resources/tag/emergency-planning) - [MONITORING](https://info.gaylord.com/resources/tag/monitoring) - [SILICA GEL](https://info.gaylord.com/resources/tag/silica-gel) - [MUSEUM STORAGE](https://info.gaylord.com/resources/tag/museum-storage) - [WEBINARS](https://info.gaylord.com/resources/webinar-archive) Search toggle What are you looking for? Search # Archival Terminology Explained ![Archival Terminology Explained](https://info.gaylord.com/hubfs/Blog_AK/ArchivalTerminology.png) Navigating the world of archives can feel like deciphering a secret language. Terms like "acid-free," "archival polyester," and "deacidification" might sound like something out of a chemistry lab. Still, they are essential concepts for anyone interested in preserving historical documents, photographs, and other valuable materials. We aim to demystify these terms, providing clear and concise definitions to help you better understand the principles and practices of archival preservation. --- ## Acid Acids are substances that can dissolve in water and can do things like make things corrode. They can weaken things like paper, making them brittle and likely to crumble. Think of old newspapers that turn yellow and crumble—that is often because of the paper's high acid content. Acids can get into paper in different ways. Sometimes, they're added on purpose during manufacturing. Acids can also migrate from other materials or even from pollution in the air. See also [Acid-Free](https://info.gaylord.com/resources/archival-terminology-explained#acid-free), [pH,](https://info.gaylord.com/resources/archival-terminology-explained#ph) [acid migration](https://info.gaylord.com/resources/archival-terminology-explained#acid-migration). ## Acid-free Paper or board that has a pH of 7.0 or higher, meaning it's not acidic. Sometimes people incorrectly call it "alkaline" or "buffered," but "acid-free" just means it's not acidic. Acid-free paper can be made from different materials like cotton or wood, but the important thing is that the acid is removed during the paper-making process. However, even if paper is acid-free when it's manufactured, it can still become acidic over time because of acid migration from stored materials. To prevent this, paper is sometimes treated with a special ingredient called a buffer, which helps to neutralize any acid that might form later on. [Learn more about what acid-free and lignin-free mean \>](https://info.gaylord.com/resources/what-does-that-mean-acid-lignin-free) ## Acid Migration This is when acid moves from something acidic (like a piece of paper that's already turning yellow) to something that's not acidic (like a clean piece of paper). It's like the acid is "spreading." This can happen when the two things are touching each other. For example, acid can move from the cardboard covers of old books to the pages inside, making those pages acidic too. ## Alkaline Alkaline substances have a pH over 7.0. They may be added to materials to neutralize acids or as an alkaline reserve or buffer for the purpose of counteracting acids that may form in the future. A buffer may be added in manufacture or during the process of deacidification. While a number of chemicals may be used as buffers, the most common are magnesium carbonate and calcium carbonate. See also [Buffer](https://info.gaylord.com/resources/archival-terminology-explained#buffer), [Calcium Carbonate](https://info.gaylord.com/resources/archival-terminology-explained#calcium-carbonate)and [Unbuffered](https://info.gaylord.com/resources/archival-terminology-explained#unbuffered). ## Archival, Archivally Sound A non-technical term suggesting a material or product is permanent or chemically stable and can be used safely for preservation purposes. The phrase is not quantifiable; no standards exist that describe how long an "archival" or "archivally sound" material will last. [Learn more why archival-quality is more than just acid-free \>](https://info.gaylord.com/resources/why-archival) ## Archival Polyester This type of clear plastic is often used to protect important documents and photos. It's strong, see-through, and doesn't have any color. Because it doesn't react with other chemicals, it's great for preservation. You'll often find it as clear sheets or film used to make things like folders, protective sleeves for documents (encapsulation), and book covers. The thickness of the plastic is measured in "mils" (very tiny units). You might know it by brand names like Mylar® or Melinex®. [Learn more about plastics for preservation \>](https://info.gaylord.com/resources/choose-the-right-plastic) ## Buffer, Buffering Agent An alkaline substance used to neutralize acid in paper and boards. See [Alkaline](https://info.gaylord.com/resources/archival-terminology-explained#alkaline)and [Calcium Carbonate](https://info.gaylord.com/resources/archival-terminology-explained#calcium-carbonate). ## Calcium Carbonate An alkaline chemical used as a buffer in papers and boards. See [Acid Migration](https://info.gaylord.com/resources/archival-terminology-explained#acid-migration). ## Cellulose This is the main building block of all plants. It's what makes up the walls of plant cells. You'll also find a lot of cellulose in things made from plants, like paper and some fabrics. ## Chemical Stability This means something doesn't easily break down or change when it's around other chemicals. It's a good thing for preservation! Think of it like this: you want the materials you use to protect old books and documents to stay the same over time. You *don't* want them to fall apart or damage the things they're supposed to be protecting. Materials with good chemical stability are strong and can resist things like paper turning brittle. Some other words that mean the same thing are "inert," "stable," and "chemically inert." ## Conservation The profession devoted to the preservation of cultural property for the future. Conservation activities include examination, documentation, treatment, and preventive care, supported by research and education. See also [Preservation](https://info.gaylord.com/resources/archival-terminology-explained#preservation)and [Restoration](https://info.gaylord.com/resources/archival-terminology-explained#restoration). ## Deacidification A common term for a chemical treatment that neutralizes acid in a material such as paper and deposits an alkaline buffer to counteract future acid attack. Deacidification technically refers only to the neutralization of acids present at time of treatment, not to the deposit of a buffer. The term is being replaced with the more accurate phrase "neutralization and alkalization." While deacidification increases chemical stability of paper, it does not restore strength or flexibility to brittle materials. See also [pH](https://info.gaylord.com/resources/archival-terminology-explained#ph). ## Encapsulation Think of this as giving a document or photo a clear plastic sandwich. You put the item between two sheets of clear plastic film (usually polyester) and then seal all the edges. This protects the item from dirt, dust, and handling. However, it's important to know that even inside this plastic "capsule," the item can still break down over time. This could be because of problems already in the item or because moisture gets trapped inside. The good thing is, you can easily remove the item later by simply cutting open the edges of the plastic, because the plastic doesn't stick to the item. ## Fiberboard Paperboard made of laminated sheets of heavily pressed fiber. ## Friable Easily crumbled. ## Inert See [Chemical Stability](https://info.gaylord.com/resources/archival-terminology-explained#chemical-stability) ## Lignin This is a natural substance found in plants, along with cellulose. It's what makes plants strong and stiff. But, when lignin is present in paper, it's believed to speed up the paper's breakdown over time. That's why paper companies often try to remove as much lignin as possible during the paper-making process. You might see paper labeled "lignin-free," but there's no official standard for what that means. Scientists are still learning about exactly how lignin affects paper, so "lignin-free" doesn't guarantee that the paper will last a super long time. [Learn more about what acid-free and lignin-free mean \>](https://info.gaylord.com/resources/what-does-that-mean-acid-lignin-free) ## Mil Unit of thickness equalling one thousandth of an inch (0.001"). ## Melinex® See [Archival Polyester](https://info.gaylord.com/resources/archival-terminology-explained#archival-polyester) ## Mylar® See [Archival Polyester](https://info.gaylord.com/resources/archival-terminology-explained#archival-polyester) ## Neutral Having a pH of 7; neither acid nor alkaline. ## pH In chemistry, pH- the measure of the concentration of hydrogen ions in a solution- determines acidity or alkalinity. The pH scale runs from 0 to 14, and each number indicates a ten-fold increase. Seven is pH neutral; numbers below 7 indicate increasing acidity, with 1 being most acid. Numbers above 7 indicate increasing alkalinity, with 14 being most alkaline. Paper with a pH below 5 is considered highly acidic. Buffered storage materials typically have a pH between 7 and 9. See also [Acid](https://info.gaylord.com/resources/archival-terminology-explained#Acid); [Alkaline](https://info.gaylord.com/resources/archival-terminology-explained#alkaline). ![The pH Scale](https://info.gaylord.com/hs-fs/hubfs/Blog_AK/PH_ScaleGraphic.gif?width=1113&height=373&name=PH_ScaleGraphic.gif) ## Permanence This refers to how well a material resists breaking down over time due to chemical reactions. It's hard to measure exactly. When you see paper labeled "permanent," it usually means it's made of a special type of alkaline paper that follows certain standards. But even "permanent" paper will only last if it's stored properly! Things like temperature, humidity, and light can still damage it. See also [Chemical Stability](https://info.gaylord.com/resources/archival-terminology-explained#chemical-stability). ## Point A unit of thickness of paper or board; one-thousandth of an inch. E.g. 0.060" equals sixty points. See also [Mil](https://info.gaylord.com/resources/archival-terminology-explained#mil). ## Polyethylene This is a type of plastic that's flexible, clear (or partly clear), and doesn't react with other chemicals. It's used in preservation to make protective sleeves for photos, among many other things. [Learn more about plastics for preservation \>](https://info.gaylord.com/resources/choose-the-right-plastic) ## Polypropylene A stiff, heat-resistant, chemically inert plastic. Common uses in preservation include sleeves for photographic materials. [Learn more about plastics for preservation \>](https://info.gaylord.com/resources/choose-the-right-plastic) ## Polyvinyl Acetate A plastic usually abbreviated as PVA. A colorless transparent material often used in adhesives, also referred to as PVA or PVA adhesive. While there are dozens or PVA adhesives, some are "internally plasticized" and are suitable for use in conservation, due mainly to greater chemical stability. ## Polyvinyl Chloride (PVC) A plastic, often abbreviated as PVC. It is not as chemically stable as some other plastics, and will emit hydrochloric acid (which, in turn, can damage library materials) as it deteriorates. It has not safe for preservation of any materials. See also [Vinyl](https://info.gaylord.com/resources/archival-terminology-explained#vinyl). [Learn more about plastics for preservation \>](https://info.gaylord.com/resources/choose-the-right-plastic) ## Preservation The protection of cultural property through activities that minimize chemical and physical deterioration and damage and that prevent loss of informational content. The primary goal of preservation is to prolong the existence of cultural property. See also [Conservation](https://info.gaylord.com/resources/archival-terminology-explained#conservation)and [Restoration](https://info.gaylord.com/resources/archival-terminology-explained#restoration). ## Pressboard A tough, dense, highly glazed paperboard. Used where strength and stiffness are required of a relatively thin (e.g. .030") board. Almost as hard as a sheet of fiber board, it is commonly used for the covers of notebooks. See also [Fiberboard](https://info.gaylord.com/resources/archival-terminology-explained#fiberboard). ## Reversibility Ability to undo a process of treatment with no change to the object. Reversibility is an important goal of conservation treatment, but it must be balanced with other treatment goals and options. ## Restoration Treatment procedures intended to return cultural property to a known or assumed state, often through the addition of non-original material. See also [Conservation](https://info.gaylord.com/resources/archival-terminology-explained#conservation)and [Preservation](https://info.gaylord.com/resources/archival-terminology-explained#preservation). ## Sizings Chemicals added to paper making it less absorbent so that inks applied will not bleed. Acidic sizings can be harmful and can cause paper to deteriorate, but some are not acidic and are expected to be more chemically stable. ## Solid Board A paper board made of the same material throughout. Distinct from combination board where two or more types of fiber stock are used in layers. See also [Fiberboard](https://info.gaylord.com/resources/archival-terminology-explained#fiberboard)and [Pressboard](https://info.gaylord.com/resources/archival-terminology-explained#pressboard). ## Unbuffered Paper or board that does not contain an [alkaline](https://info.gaylord.com/resources/archival-terminology-explained#alkaline)buffer. While a buffering agent help protect against [acid](https://info.gaylord.com/resources/archival-terminology-explained#Acid) damage, some special items need to be stored with unbuffered paper because the buffer could harm them.   [Learn more about choosing buffered or unbuffered storage materials \>](https://info.gaylord.com/resources/buffered-or-unbuffered) ## UV Filter A material used to filter the ultraviolet (UV) rays out of visible light. Ultraviolet radiation is potentially damaging to library, archival and museum objects. More is present in sunlight and fluorescent light than incandescent light. Removing UV radiation throughout museum spaces can reduce the rate of deterioration of materials. A UV filtering material can be placed over windows, fluorescent light tubes, or glass used in framing and exhibition cases. Certain acrylic sheet materials have UV filtering properties built in. ## Vinyl The word vinyl is imprecisely used to refer to any of a number of plastics, many of which are not appropriate for use in preservation. For safe plastics, see [Polyester](https://info.gaylord.com/resources/archival-terminology-explained#archival-polyester), [Polypropylene](https://info.gaylord.com/resources/archival-terminology-explained#polypropylene), [Polyethylene](https://info.gaylord.com/resources/archival-terminology-explained#polyethylene) and [Polyvinyl Acetate](https://info.gaylord.com/resources/archival-terminology-explained#polyvinyl-acetate). ##### LEarn More: - [What is Conservation?](https://www.culturalheritage.org/about-conservation/what-is-conservation) - American Institute of Conservation (AIC) - [Introduction to Preservation](https://www.nedcc.org/preservation101/session-1/1what-is-preservation) - Northeast Document Conservation Center (NEDCC) - [Preservation](https://siarchives.si.edu/what-we-do/preservation)- Smithsonian Institution Archives - [Conserve, Preserve, Restore: What's the Difference?](https://www.history.sa.gov.au/resource/conserve-preserve-restore-what-is-the-difference/) - History Trust of South Australia - [Preservation: Getting Started](https://www.nps.gov/subjects/museums/upload/MHI_Ch3_Preservation_GettingStarted.pdf) - National Park Service (NPS) - [Dictionary of Archives Terminology](https://dictionary.archivists.org/index.html)- Society of American Archivists (SAA) ### Share: [Share on Facebook](http://www.facebook.com/share.php?u=https://info.gaylord.com/resources/archival-terminology-explained&utm_medium=social&utm_source=facebook) [Share on LinkedIn](http://www.linkedin.com/shareArticle?mini=true&url=https://info.gaylord.com/resources/archival-terminology-explained&utm_medium=social&utm_source=linkedin) [Share on X](https://twitter.com/intent/tweet?original_referer=https://info.gaylord.com/resources/archival-terminology-explained&utm_medium=social&utm_source=twitter&url=https://info.gaylord.com/resources/archival-terminology-explained&utm_medium=social&utm_source=twitter&source=tweetbutton&text=Archival%20Terminology%20Explained) [Archival Basics](https://info.gaylord.com/resources/tag/archival-basics), [Preservation](https://info.gaylord.com/resources/tag/preservation) ## Related posts Resources provided here are based on general circumstances. Depending on the condition and significance of your collection, it may require special care. Certain actions may cause irreversible damage. When in doubt, [Find an Expert \>](https://community.culturalheritage.org/expertsearch) ### Are we missing something? If you can't find the information you're looking for, we want to know! [Suggest a Resource \>](https://www.surveymonkey.com/r/VFG5D5S) ![Gaylord Archival: Preserve Today. Share Tomorrow.](https://info.gaylord.com/hs-fs/hubfs/Gaylord%20Archival%20Logos%20-%20Horizontal-02.png?width=500&name=Gaylord%20Archival%20Logos%20-%20Horizontal-02.png "Gaylord Archival: Preserve Today. Share Tomorrow.") # Shop - [Preservation](http://www.gaylord.com/c/Preservation) - [Exhibit & Display](http://www.gaylord.com/c/Exhibit-and-Display) - [Environmental Control](http://www.gaylord.com/c/Environmental-Control) - [Storage & Handling](http://www.gaylord.com/c/Storage-and-Handling) - [Family History/Collectors](http://www.gaylord.com/c/Family-and-Collectors) - [New Products](http://www.gaylord.com/c/New) # Let Us Help You - [Contact](https://www.gaylord.com/contact) - [Returns](https://www.gaylord.com/returns) - [Shipping](https://www.gaylord.com/shipping) - [FAQs](https://www.gaylord.com/frequently-asked-questions) - [100% Satisfaction Guarantee](https://www.gaylord.com/satisfaction-guarantee) - [Catalogs & Guides](https://www.gaylord.com/request-a-catalog) - [Order by Part #](https://www.gaylord.com/quick-order) Copyright © 2025 Gaylord. All rights reserved. [Privacy Policy](https://www.gaylord.com/privacy-policy) | [Accessibility](https://www.gaylord.com/accessibility)