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 varieties, it is far more difficult to spot grades. It needs to be understood that most paper and card is manufactured for a specific purpose, so that whilst corn-flake packet may look smart it is clearly not something destined for 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 word ‘paper’. Many of these are very specialized, but preponderance of paper making has been from soft wood and cotton or rags, with 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 final product is made, relying on bonding together of cellulose into layers. That, in a very small nutshell, is essence of paper making from wood. However, reality is rather more complicated. In order to give us our white paper and card 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 tree since it holds cellulose fibres together, but if it is incorporated into manufactured paper it presents archivists with a problem. Lignin eventually breaks down and releases acid products into paper. This will weaken bond between cellulose fibres and 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 lignin can be removed from paper pulp during manufacture obvious question is ‘why is it left in paper?’ The answer lies in fact that lignin makes up a considerable part of tree. By leaving lignin in 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 lignin for many paper and card applications.