英语学习资料：2012年6月大学英语六级快速阅读冲刺（1） 以下文字资料是由小编为大家搜集整理后发布的内容，让我们赶快一起来看一下吧！
Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1.
For questions 1-7, choose the best answer from the four choices marked [A], [B], [ C] and [D ]. For questions 8-10, plete the sentences with the information given in the passage.
Paper–More than Meets the Eye
We are surrounded by so much paper and card that it is easy to forget just how plex 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 fibers 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 plicated. 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.
A 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 fibers and the paper will bee 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
