闻香识书

By+Karl+Kruszelnicki

If youre into reading， youll probably have noticed how a brand new book has a rather special smell. Yes， its that new book smell—and its quite different from the smell of an older book. Whats going on？

Books have been around for about 4，500 years. Some of the earliest books come from the fifth dynasty of Egypt， about 2，400 BC. They were written on papyrus1—similar to modern paper， but thicker.

They made papyrus sheets by weaving together the stems of the papyrus plant into a sheet， and then smoothing out the bumps by pounding the woven sheet with some kind of mallet.2 But these were scrolls， a continuous roll of paper， rather than “the book” as we think of it today， which is a collection of individual sheets， stuck together along one edge so that the pages hinge3 on that side.

The book， in its modern form， began to appear around the first century AD. These books had the advantages of being easier to read than a scroll， easier to find a specific page， and you could stack4 them more efficiently than you could with scrolls.

In the early days， books were heavy and cumbersome5. Each book had to be made individually by hand—with every word on every page written by a scribe.

So by 800 AD， a large library might hold only 500 books. Around 1045 AD， the Chinese inventor， Bi Sheng， came up with movable type made of earthenware—mud or clay， not metal.

Unfortunately， neither his printing press nor any books made with it have yet been found.

So the credit usually goes to Johannes Gutenberg for devising the printing press with movable type.6 He independently invented it around 1450 AD.

Suddenly， books could be produced much more rapidly. Adding steam power meant that by 1800 AD， a printing press could deliver over 1，000 sheets per hour.

So， where does the smell come from？ Three sources—the paper， the ink and the glue.

The Chinese first came up with paper like our modern paper around 200 AD. This invention slowly spread westward to Muslim countries， and then to Europe.

Now theres a big difference between a lump of wood， and a sheet of paper. The wood has to be crushed， and then chemicals have to be used.

Chemicals have to be added to make the wood fibres swell， to remove acid， to bleach the paper to the desired grade of whiteness， to confer some degree of water resistance， to add a sheen to the paper， and so on.7

Thats part of the smell： each chemical comes with its own odour.

And there are many different inks. Some inks fade with time， while others get darker.

Theres a huge range of glues that can be used to bind the sheets together along one side to form a hinge. Different glues again would be used to attach the covers， whether hardcover or paperback.

So you can see that there is an enormous range of different chemicals that can waft8 out of the freshly opened pages of your brand new book.

Even within the books of one publishing house， there would be many different chemicals used， depending on the purpose of the book. A cheap black-and-white paperback would use quite different chemicals compared to an expensive coffee table book with glossy colour pages.9

The whole situation gets more complicated again as the book degrades10. Not only will the inks and glues age and break down at their own rates， so too will the lignin and the cellulose in the paper.11

These by-products include toluene （which gives a sweet odour）， vanillin （which gives， of course， a vanilla odour）， benzaldehyde （which smells like almonds） and 2-ethyl hexanol（slightly floral）.12

Indeed， some of the other breakdown products （such as furfural13） can be used to work out the age of the paper. So if you try to sell your freshly forged14 100 per cent genuine diary of the Buddha， make sure that you use paper that is older than a few years—or else your deception will be quickly detected.

Today， the evolution of books has continued into the digital revolution， with eBooks. They might be convenient， but you cant give your copy to another person as a present， and they dont smell as nice.

如果你愛读书，可能你曾注意到：一本崭新的书会散发出一股奇特的气味。没错，那就是新书的味道，与旧书的相去甚远。其中奥妙何在？

书的历史可追溯至大概4500年之前。公元前2400年左右，埃及第五王朝的一些书应属最早的书籍之一了。它们用的是莎草纸——与现代纸张相似，但较之更厚。

埃及人把莎草的茎梗编织在一起，做成一大张莎草纸，然后用类似于木槌的工具连续砸击其凹凸不平的表面，使纸变得平滑。但那时用的纸都是卷轴，即长长的一卷纸，而非我们所认为的现代意义上的“书籍”——纸被裁成一张一张的，沿一侧粘贴起来，形成书脊。

公元一世纪左右，现代书籍开始出现，这样的书籍与卷轴相比更便于阅读，更容易翻到某一页，也能更好地摞起来。

早期书籍过于笨重，成书过程复杂繁琐。每本书都是“手工”制作—— 古代抄写员一字一句誊写在书页上。

因此，公元800年时，一家“大型”图书馆的藏书量可能仅有500本。公元1045年左右，中国的发明家毕发明了泥活字—— 使用泥土或黏土制版，而不是金属。

不幸的是，他的印刷机和用之印制的书籍尚未被发现。

所以，人们常常将活字印刷机的发明归功于约翰尼斯·古登堡——他在公元1450年左右独立发明了活字印刷机。

忽然之间，书籍得以更快速地生产出来。到了公元1800年，蒸汽动力出现之后，一台印刷机一小时就能印刷一千余张纸。

那么，书的气味究竟从何而来？源头有三：纸、墨、胶。

公元200年左右，中国首先造出了类似现代纸张的纸。这项发明慢慢向西传到伊斯兰国家，然后再传入欧洲。

一块木头和一张纸看上去差异巨大。木材必须碾碎，然后使用各种化学药品进行处理。

加入化学药品，使木质纤维膨胀，去除酸液，漂白纸张至想要的白度，使其具有一定的防水性，增添其光泽度，造纸需要进行上述等一系列的处理工艺。

每一种化学药品都具有自己独特的气味，这就是书气味的部分来源。

印刷时还会使用许多不同种类的油墨。随着时间的推移，一些墨水慢慢褪色，另一些则越来越深。

沿书页一侧粘贴书脊时可用的胶水也是五花八门。同样，在粘贴封面时——无论是精装还是平装——也会用到不同的胶水。

因此，当你刚刚打开一本崭新的书时，一大堆各种各样的化学品的气味扑鼻而来。

即使是同一个出版社的书，书的定位不同，所用的化学品亦会不同。单色的廉价平装书所用的化学品必然与亮丽的彩色印刷的昂贵咖啡桌配书完全不同。

随着书籍的年头越来越长，情况又愈加复杂起来。不光油墨和胶水会以各自的速度老化、分解，纸张中的木质素和纤维素也同样在降解。

这一过程产生的副产品包括甲苯（散发甜甜的气味）、香草醛（显然，有香草的气味）、苯甲醛（闻起来像杏仁）和2-乙基己醇（微带花香）。

事实上，其他一些分解产物（例如糠醛）可用于检测纸张的年代。所以，如果你想成功地售出一本新鲜炮制的“百分百正宗”的佛陀日记，那么你必须确保用纸有一定的年头——不然，骗局很快会被拆穿。

如今，随着电子书的诞生，书籍的进化已经进入了数字革命时代。电子书倒是携带方便，可是你没法将它们作为礼物赠送他人，而且它们闻起来可没有纸书这么好。

1. papyrus：（古埃及人用的）莎草纸。

2. stem： （植物的）茎，梗；bump：隆起之处；pound： 连续重击，猛打；mallet： 木槌。

3. hinge： 给……装铰链。此处指用胶或线等方式把书页黏合起来。

4. stack： 整齐地堆起，摞起。

5. cumbersome：（过程或系统）耗时的，累赘的。

6. credit： 功劳，赞誉；Johannes Gutenberg：约翰内斯·古登堡（1398—1468），是第一位发明活字印刷术的欧洲人，他的发明引发了一次媒介革命，并被广泛认为是现代史上最重要的事件之一。

7. swell： 鼓起，隆起；bleach： 使变白，漂白；confer： 赋予，带来；sheen：（外表的）光泽，光彩。

8. waft： （在空气中）飘荡。

9. coffee table book： 咖啡桌图书，一般是供咖啡茶几上摆设用的书或大型画册；glossy： 光亮的，有光泽的。

10. degrade： 降低……的質量（或品格）。

11. lignin： 木质素；cellulose： 纤维素。

12. toluene： 甲苯，一种无色、带特殊芳香气味的挥发液体；vanillin： 香草醛，又名香兰素，一种白色至淡黄色针状结晶的有机化合物，可从香草种荚中提取；benzaldehyde：苯甲醛，有机化合物，在室温下是无色液体，具有特殊的杏仁气味；2-ethyl hexanol： 2-乙基己醇，无色有特殊气味液体，可燃；floral： 像花的。

13. furfural： 糠醛，一种工业用化学制品，一种芳香族的醛。

14. forge： 伪造。