Hi Phaedra

I feel I should point out as a matter of urgency that spot checks using this sort of pH pen will not serve to check the suitability of paper for it's use to make  archival enclosures nor anticipate the lifespan of paper collections amongst archives.  

This is because paper that is 'acid free' now, or at the time of manufacture may become acidic over time, especially if kept in less than perfect storage conditions and contains lignin.  Only documents that are to be kept in the short term, such as office paperwork, should be produced on standard office paper and it should not be used to make labels or placed in direct contact with archival items as they can cause damage through acid migration.  The paper enclosures and 'archival papers' that are available from specialist suppliers at high prices are expensive because they do not contain sizing, bleach residues and other manufacturing chemicals are generally made from cotton or linen fibres, rather than cheap wood pulp - so they do not contain lignin which is important.

I lifted the following from a website which may be of help:      

Q: What does “acid-free paper” mean?

A: Acid-free paper means that at the point of manufacture, the paper had a pH of 7 (neutral) or slightly above 7 (alkaline). A paper that is labelled “acid-free” with no other qualifier means the paper is currently acid-free but will probably become acidic over time. This definition applies to paper made from wood pulp. If paper is made from cotton, linen, or hemp, the longevity of the paper greatly increases.

Q: What does “lignin-free paper” mean?

A: Lignin is found in wood pulp and is the substance that exacerbates acidity. Lignin can be removed in the pulping process. It is expensive, but the resulting paper will remain acid-free much longer than wood pulp paper in which lignin is present. When newspaper turns brown over time, this is due to the lignin causing acid to form within the paper fibres.

Q: What does “buffered paper” mean?

A: Buffered paper means that a buffering agent, usually calcium carbonate, has been added to the paper pulp in order to neutralize any acids formed in the paper over time and make the product slightly alkaline. Paper that has had the lignin removed is the most likely candidate to also have a buffering agent added. This type of paper has very good longevity but is not suitable for the storage of some media i.e some photographic processes (see guidelines below).  Lignin can be even more harmful to photos than acid.


Guidelines:

·        Mount boards should be 100% cotton fibre and all papers should be made of new ‘rag’ (cotton or linen) pulp, or fully bleached chemical wood pulp with a high alpha cellulose content (above 87%) and pH of 6-9.  (Both should be free of ground wood, lignin, acid, alum-rosin, metal particles, waxes, plasticizers. and have less than a 0.0008 percent reducible sulphur content).  Some items benefit from packaging with a 2-3% calcium carbonate alkaline reserve.

·        Photos should be stored in non-buffered paper with a pH of 6 that is free of chloride, sulphur and lignin. 100% cotton fibre is recommended.  All materials must pass the PAT silver tarnish test (i.e. the Photographic Activity Test).

·        Labels should be made of archival paper with pressure sensitive acrylic adhesive.

kind regards

Suzanne Breeze (Conservator) Birmingham






Phaedra Casey <[log in to unmask]>
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11/07/2012 12:12
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pH Testing pen





Dear all
 
Further to my recent post about acid-free paper suppliers, may I draw your attention to Gresswell’s “Abbey pH Pen”, which can be used to check if your general-use paper is acidic.  They work out at about £5 each.
 
Mine has just arrived so I am now merrily checking all my paper!  It turns out that our normal printer paper is non-acidic. 
 
Many thanks to Joanne Wishart of Shetland Archives who suggested checking our usual paper.
 
Best wishes
 
Phaedra
 
Phaedra Casey
Archivist
Brunel University Archives
Kingston Lane
Uxbridge
Middlesex UB8 3PH
 
01895 267095
 
Please note that the Archives have now moved to Uxbridge. 
 

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