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Paper - More than Meets the Eye
We are surrounded by so much paper and card that it is easy to
forget just how complex it is. There are many varieties and grades
of paper materials, and whilst it is fairly easy to spot the varieties,
it is far more difficult to spot the grades.
It needs to be understood that most paper and card is manufactured
for a specific purpose, so that whilst the corn-flake packet may
look smart it is clearly not something destined for the archives.
It is made to look good, but only needs a limited life span. It
is also much cheaper to manufacture than high grade card.
Paper can be made from an almost endless variety of cellulose
based material which will include many woods, cottons and grasses
or which papyrus is an example and from where we get the word
‘paper’. Many of these are very specialized, but the
preponderance of paper making has been from soft wood and cotton
or rags, with the bulk being wood based.
Paper from Wood.
In order to make wood into paper it needs to be broken down into
fine strands. Firstly by powerful machinery and then boiled with
strong alkalies such as caustic soda, until a fine pulp of cellulose
fibres is produced. It is from this pulp that the final product
is made, relying on the bonding together of the cellulose into
layers. That, in a very small nutshell, is the essence of paper
making from wood. However, the reality is rather more complicated.
In order to give us our white paper and card the makers will add
bleach and other materials such as china clay and additional chemicals.
An further problem with wood is that it contains a material that
is not cellulose. Something called Lignin. This is essential for
the tree since it holds the cellulose fibres together, but if
it is incorporated into the manufactured paper it presents archivists
with a problem. Lignin eventually breaks down and releases acid
products into the paper. This will weaken the bond between the
cellulose fibres and the paper will become brittle and look rather
brown and careworn. We have all seen this in old newspapers and
cheap paperback books. It has been estimated that most paper back
books will have a life of not greater than fifty years. Not what
we need for our archives.
Since the lignin can be removed from the paper pulp during manufacture
the obvious question is ‘why is it left in the paper?’
The answer lies in the fact that lignin makes up a considerable
part of the tree. By leaving the lignin in the pulp a papermaker
can increase his paper yield from a tree to some 95%. Removing
it means a yield of only 35%. It is clearly uneconomic to remove
the lignin for many paper and card applications.
It also means, of course, that lignin free paper is going to
be more expensive, but that is nevertheless what the archivist
must look for in his supplies. There is no point whatsoever in
carefully placing our valuable artifacts in paper or card that
is going to hasten their demise. Acid is particularly harmful
to photographic materials, causing them to fade and is some cases
simply vanish!
So, how do we tell a piece of suitable paper or card from one
that is unsuitable? You cannot do it by simply looking, and rather
disappointingly, you cannot always rely on the label. ‘Acid
free’ might be true inasmuch as a test on the paper may indicate
that it is a neutral material at this time. But lignin can take
years before it starts the inevitable process of breaking down,
and in the right conditions it will speed up enormously.
Added to this, as I have indicated earlier, paper may also contain
other materials added during manufacture such as bleach, china
clay, chemical whiteners and size. This looks like a bleak picture,
and it would be but for the fact that there are suppliers who
will guarantee the material that they sell. If you want to be
absolutely sure that you are storing in, or printing on, the correct
material then this is probably the only way.
Incidentally, acids can migrate from material to material. Lining
old shoe boxes with good quality acid free paper will do little
to guard the contents. The acid will get there in the end.
Paper from Rag.
Paper is also commonly made from cotton and rag waste. This has
the advantage of being lignin free, but because there is much
less cotton and rag than trees, it also tends to be much more
expensive than wood pulp paper. You will still need to purchase
from a reliable source though, since even rag paper and card can
contain undesirable additives.
A reliable source for quality rag papers is a recognised art
stockist. Many water colour artists insist on using only fine
quality rag paper and board.
The main lesson to learn from this information is that you cannot
rely on purchasing archival materials from the high street. The
only safe solution is to purchase from specialist suppliers. It
may cost rather more, but in the end you will know that your important
and valuable data and images have the best home possible.
About the Author
Peter Amsden has many years experience in photography, film and
television. An Associate of both The Royal Photographic Society
and of the British Institute of Professional Photographers. He
had made a special study of conserving and archiving imaging media
and is author of "Images for the Future". Runs consultancy
and web design business. http://www.ASAT.biz
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