The conservation of photographs is a key challenge in the field of heritage preservation, as these objects are particularly susceptible to chemical and physical deterioration. Among the various factors that influence their longevity, the type of materials used for storage and packaging plays a decisive role. In this context, the use of acid-free paper stands out as a fundamental practice.
Ordinary paper, which is often acidic due to industrial manufacturing processes, can accelerate the deterioration of photographs, causing yellowing, brittleness and loss of image quality. In contrast, acid free paper is produced to have a neutral or slightly alkaline pH, significantly reducing the risks of degradation. Thus, its use in envelopes, boxes and interleaves contributes directly to the long-term stability and preservation of photographic collections.
This article explores the reasons why acid-free paper is essential for the conservation of photographs, discussing its benefits and practical applications, and clarifying common questions on the subject.
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Learn more about this subject in the online course Preventive Conservation of Photography.
What is photo deterioration?
Deterioration is basically any physical and chemical transformation occurring after processing.
It usually consists of a change in the original colour, or the fading and the loss of contrast of the image,…
It can have various forms and origins, such as changes in temperature and humidity, the formation of fungi, animal or insect infestations, among others.
How to avoid this by using acid free paper
Improper packaging may also potentiate its degradation. For this reason, the most recommended material is acid free paper .
But, what does this mean…?
The acid that exists in most papers and tissues causes several changes in photographs, weakening them with time. The paper gets stained, ages and dries out, the image fades out progressively, the emulsion gets pasty or breaks…
What is acid free paper
In 1930, William Barrow concluded that paper itself deteriorated over time and that, without the proper control of its acidity level, the contact with the light itself can wear out and affect the composition of paper.
Thus, it becomes important that the paper has a neutral (or basic) chemical composition, with a pH equal to or slightly higher than 7.0.
Acid free paper then began to be used in the context of archives and museums.
The manufacturing process of this paper implies the treatment with calcium carbonate (which is called an alkaline reserve) that neutralizes the acids naturally created by cellulose.
Acid Free paper or Alkaline paper
In this way, it can be ensured that papers with this treatment maintain their alkalinity for at least 100 years, favouring the conservation processes of the photographs.
However, if you want to conserve albumins, chromogenic or dye-transfer processes, paper with an alkaline reserve is not recommended because it can react with the compounds in the photograph.
Another important detail is to guarantee that the paper is equally free of lignin.
Lignin is a chemical compound naturally present in cellulose, whose oxidation acidifies and stains the paper.
It is the main responsible for the appearance of yellow spots.
How to identify acid free paper
Acid free paper generally presents a quality certificate where you can read its main characteristics and tests to which it has been subjected.
In some cases, standards such as ISO18902 and ISO18916 are specified, but it is not crucial they be mentioned.
The Image Permanence Institute (IPI) website has more information about the tests made for photographic papers.
Points to consider when choosing paper for preserving photos
If you are looking for paper to store your file or photo album, keep these basic points in mind:
- it is important the paper has a neutral pH,
- is acid and lignin free,
- it may or may not have an alkaline reserve (make sure your photos are secure with it)
- and search for duly certified paper so as to ensure its quality, efficacy and durability.
Study the needs of your photos and suit the materials to them.
Learn how to do a photo storage program of our private collections.
