Archival Definitions: Acid Free / Buffered / Unbuffered
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The term Acid Free gets tossed around a lot!
… just WHAT does “acid-free” actually mean???
First, a quick review: Remember 7th grade science class all those zillions of years ago?
Now, just HOW does this apply to your …
Collectibles • Artwork • Family Heirlooms • Works on Paper • Photographs • Fabrics • Everything Else
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High Acid Content can Destroy YOUR Collections & Archives
The acid content in a paper is the best indicator of its life expectancy. Acid free means that the paper’s pH is 7.0 (neutral) or higher (alkaline). Acid free papers will last up to 200 years under normal use and storage conditions.
In terms of vintage paper and cardboard, each of these materials react differently to sunlight, temperature, and humidity – more often than not with damaging results. Over time, certain chemicals that were either naturally present in the paper or were perhaps introduced during the manufacturing process may become “activated,” affecting the paper or cardboard in very destructive ways.
Perhaps the best example of paper “destroying itself from the inside” is seen in old newsprint and the paper used for many old books from the late-1800s / early-1900s, much of which is now yellowed (if not brown) and very brittle.
Lignin is a naturally occurring acid that is often present in the wood pulp slurry used to create the paper. The yellowing and brittleness of old papers is due to lignin and other residual acids becoming “activated” by humidity and temperature in a process that often ends up destroying the paper itself.
An extreme example of high acid content in paper can be seen in the page fragment below, which came from an old book on World War I, c.1920.
In addition to “breaking off” from the larger page this fragment was originally a part of, when slightly bent this brittle, acid-burned page cracked and fell apart, as its structural integrity had been compromised by the high acid content of the paper.
There is not much that can be done to mitigate THAT level of internal acid damage, other than to carefully scan the original and make copies, and then perhaps consult a trained, professional conservator. (Please click here to see our blog entitled “Conservators – Pros You Should Know.”)
In addition, in order to maintain a safe, long-term archival environment, and to minimize any chance of “acid-migration” from your artworks or artifacts, most of our acid free materials are “buffered” with 2-3% calcium carbonate.
This calcium carbonate “buffering” provides our museum-quality storage and presentation materials with an archivally-safe pH of 9 (±0.5), which will help neutralize any acids that might migrate from your artifacts or artworks.
While “buffered” acid free mat boards / boxes / envelopes / & interleaving tissues are what are most commonly recommended for most archival storage and presentation needs, there are exceptions – especially for certain fabrics and photographic processes.
When storing “vegetable” based fabrics or artifacts (such as cotton), either “buffered” or “un-buffered” Archival Tissue can be used.
When storing “protein” based fabrics or artifacts (such as silk or wool), one should always use “un-buffered” Archival Tissue, as these fabrics should not be exposed to direct contact with standard 2-3% calcium carbonate buffering agents.
As mentioned, certain photographic processes – such as cyanotypes (blue prints) & dye-transfer prints – “just don’t like” calcium carbonate buffering agents, which can harm them. These types of images should be interleaved with “un-buffered” Archival Tissue.
Cyanotypes (see photo below) and dye-transfer prints can also be placed in archival Polyethylene Bags before they are stored in buffered acid-free enclosures and boxes – the PERFECT archival solution.
Of note, there are some older photographic conservation guides that suggest that the dyes in chemically processed color photographic prints can be harmed by exposure to calcium carbonate buffering agents.
More contemporary research, however, has indicated that this is usually not the case – unless your color photograph AND your interleaving material BOTH get wet, see explanation below.
In practice, since calcium carbonate buffering agents do not “migrate” like some acids can, using “buffered” mat boards and interleaving is fine, as exposure to liquid water is required – both the archival interleaving paper or tissue AND the gelatin layer of the print itself getting wet – for there to be any transfer of buffering agents to your print.
Using “buffered” mats and interleaving should therefore be considered for use with color photographs, because if your interleaving material and the print itself get wet then you have even greater problems than anything caused by the potential transfer of buffering agents. If you’re still in doubt, however, go with “unbuffered” Archival Tissue.
And that, folks, is what’s up with the terms “acid free” / “buffered” / & “un-buffered.”
You can rest assured that your important artwork, photographs, collectibles, papers, fabrics and artifacts from the family archive are safely protected for generations to come in their “acid free” enclosures, boxes and mats.
Lastly, as a quick 5-minute review of everything mentioned in this blog, please watch our short / comprehensive YouTube video on Archival Methods Definitions / Differences: Acid-Free / Buffered / Unbuffered!
If you have any additional questions regarding “acid-free” storage or presentation, or whether “buffered” or “un-buffered” materials are right for your needs and applications, please contact us here at Archival Methods. We’re always there to help with any archiving, storage, or presentation questions you may have.
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