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Why acid-free enclosures?

In our daily contact with customers, we often encounter the following questions: What does it mean that an enclosure is acid-free? Do books and documents should really be stored in special packagings? Don't ordinary ring-binders and folders, available in each stationary, suffice?

The answer is no, ordinary packagings are not sufficient if we wish to preserve the good state of a document, a book or a photo for longer time than several years. Common boxes, ring-binders and folders offered in stationery shops are mostly used to keep documents in order and well organized. However, they cannot be applied for a long-term storage and preservation since the boards they are made of might be acidic or equipped with harmful components like brightening agents. In this case, such enclosures will not protect documents from degradation but they will accelerate it. How is that possible? Unfortunately, that is the nature of paper; cellulose fibres, the main matter of paper, disintegrate under the influence of acids. We all held a book or a newspaper issued a few decades ago which pages turned yellow or even brown and became extremely brittle. It happens mostly because of acids e.g. sulphur and nitrogen compounds present in polluted air. The biggest problem, however, is that acidic components are the ingredients of paper itself. The paper produced between the mid 19th century and the end of the 20th century is called „Suicide-Paper” not without reason. Due to printing massification in this period, paper industry searched for cheaper and more efficient methods of paper production. In consequence they started mixing cellulose with wood pulp, brightening agents or glues and caused its acidification and eventually decay. We need to be aware that world's cultural heritage falls apart with disintegration of cellulose fibres. Various unique works of literature and art, documents which changed the history; all these testimonies of past slowly turn into dust, just as the newspaper from a few decades ago. This issue has been troubling archivists, librarians and scientists for many years. Some methods of de-acidification have been discovered but they remain very expensive so only the biggest libraries and archives can afford them, and even so only the most precious collections are subjected to those processes. Appropriate storage of paper plays a major role in this context. There are unavoidable harmful factors such as polluted environment or already mentioned ingredients of paper, so the aim is to add some elements which could slow down the deterioration process of paper instead of accelerating it. It is worth noting that acids can migrate from one object to another or from an enclosure to its contents. If we posses a book made of highest quality paper (pure cellulose with no brightening agents or wood pulp), which is resistant to the process of disintegration, and we store it in a box made of acidic board it will gradually acidify the book and destroy it. That is why using acid-free storage products is so important. Such enclosures shall not accelerate the disintegration of cellulose fibres, instead they will create an optimum safe environment for the stored objects and separate them from outer damaging influence.

What are the characteristics of enclosures intended for storage of archives?

Enclosures meant for long-term storage of documents, books and other paper objects should be made of materials of the following characteristics:

  • pH > 7, best between 7.5 – 10
  • Kappa number < 5
  • alkali reserve > 0,4 mol/kg (in case of calcium carbonate, paper should contain at least 2% of CaCO3)

What does it mean? The pH value informs us about (non)acidity of enclosures. pH is a numeric scale used to specify the acidity or alkalinity of an aqueous solutions, it takes values from 1 to 14. The pH value of 7 means that solution is neutral e.g. distilled water. Solutions with a pH less than 7 are acidic – enclosures made of materials of such pH accelerate the process of deterioration of records. That is why when choosing the right storage product we should note whether it's made of a material of pH value between 7.5 – 10.00. We should also bear in mind that this requirement applies to all layers of boards. The Kappa number is a parameter specifying the maximum content of oxidizing agents in paper and board. Its value should be less than 5, which can be obtained only by boards made of ~100% of pure cellulose and no wood pulp.

Alkali reserve means that a board or paper was produced with addition of basic component (usually calcium carbonate), which will neutralize acidic compounds appearing with time. Thus it will longer protect the stored object. We should also mention that enclosures meant for storage of valuable collections ought to present high mechanical resistance. That is the reason why most of our storage products are made of solid boards, which compared to corrugated boards are much more durable, rigid and resistant to soaking. The highest quality of products for a long-terms storage of paper is certified by International Standards ISO 9706:1994 and ISO 16245:2009.

Beskid Plus Company offers wide variety of enclosures manufactured of acid-free boards and papers, suitable for the long-term storage of records. You can find detailed characteristics of our materials used for production of our boxes and folders in Papers & Boards chapter. Should you have any questions or problems with choosing the right material, please contact our employees, who are well qualified and more than happy to help you finding the finest solution.

Prepared by: Zofia Parchańska-Puczek
Sources:

  • Bogacz-Walska, Monika, 1998, Główne przyczyny niszczenia materiałów archiwalnych, [w:] Archeion, T. XCIX, Warszawa
  • Hebig, Dieter, 2001, Schutzverpackungen – ein wichtiger Beitrag zur Bestanderhaltung von Archiv- und Bibliotheksgut, [w:] INFO 7, Heft 3, s. 143-150

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