For a long time wood was the principal substance used by man for building his home and provided the means to furnish it as well as the utensils to use in it. Even in this atomic age, wood is still a vitally important commodity commanding high prices and requiring large-resources of space and manpower for its production. Wood is very often used directly, the nature of use depending on the type of wood itself, but the use of’processed’ wood and wood products is discussed here.
The paper used for newspapers and books is very often manufactured from wood pulp that was once part of a forest in Scandinavia, Canada or USA. About 80 million tons of pulp are produced annually throughout the world, half to make paper other than newsprint, onethird for cardboard and about one-sixth for newsprint. Pulp is produced mainly from softwoods or conifers: two qualities of pulp are obtained, one by mechanical means (grinding) and the other by chemical means (dissolution of binding materials such as lignin to free the cellulose fibres), the latter process giving the best quality paper.
The leather industry depends upon the successful processing of animal hides to produce a tough stable leather, resistant to oxidation, moisture, extreme temperature changes and bacterial attack. An important part of this process is tanning, in which tannins (a complex group of astringent substances found almost universally in plant tissues) are allowed to combine with the proteins in the hides over a period of time which can range from a few hours to several months. Although tannins can be ob- tained from numerous sources, they are most often produced from tree bark by leaching with hot water. The tannin concentrate so produced is then used directly for the tanning process. Oak, chestnut and hemlock trees have been traditional sources of bark for tannin extraction: present-day commercial sources of importance are wattle and mangrove barks and chips of quebracho wood.
Although not directly obtained from wood, rubber can perhaps be considered as a ‘wood product’. Rubber is manufactured from the latex (a milky juice) present in the cells of several species of tropical and subtropical plants. Most important is para rubber obtained from Hevca brasiliensis, a tree first found in the forests of the Amazon and transferred in the nineteenth century to Sri Lanka and Malaysia where eventually over 90 percent of the world’s supply of rubber came to be, and still is, produced. Normally, the latex is obtained by tapping the tree trunk, using variously shaped incisions, and collecting the exuded latex in specially designed cups. After collecting, the latex is coagulated, either by acid or by smoking, and then sold for processing to make the wide variety of.articles that are so familiar to us today. Other plants, including dandelions also produce latex.
Other ‘household’ plants
Wood is not the only plant product of material use to the household. Plant products are used to clothe us, to colour our clothes and to perfume our bodies; they provide us with ropes for tying and binding and materials for basket weaving. Although many of these uses have been superseded by the discovery of synthetic substitutes there is nevertheless a sense of nostalgia in many people which encourages the continuation of traditional recipes and methods. Of these, the use of plant extracts for colouring material is perhaps one of the most interesting aspects.
The employment of colour must be as ancient as man himself and for this purpose he has always made extensive use of vegetable dyes. From their rather primitive use on parts of the body, as ornamentation or as protection against evil spirits, their use was developed extensively for dyeing clothes, a method which continues today, although most dyes are now synthetically manufactured.
In western Europe one of the earliest products was woad, a blue dye obtained from Isatis tinctoria involving a very smelly fermentation process. Combination of woad with other natural dyes such as madder powder (red) or weld (yellow) produced a wide range of other colours so that in the Middle Ages woad was referred to as ‘universal dye’. Eventually woad was supplanted by indigo, another blue dye, obtained from the plant Indigqfera tinctoria (actually containing the same blue pigment, now called indigotine) and which had been used in Asia for over 4,000 years.
Of the yellow dyes one of the most sought after was saffron, the principal yellow colouring used by the Greeks and Romans. Saffron is obtained from the yellow stigmas of a blue crocus (sativus) which is cultivated mainly in the Mediterranean area. Because it is only obtained in relatively small quantities (about 8,000 are needed for the production of loog (3 5oz) of dried saffron) the use of saffron as a dye has been replaced by cheaper substitutes, but it is still valued as a food additive.
For producing a red colour one of the most important dyes was obtained from the madder plant (Rubia tinctorum). The red pigment can be extracted from the-stock and may have been first used in India although it was well-known to the Persians and ancient Egyptians. With the advent of modern synthetic dyes the use of madder for dyeing has been superseded although it is still produced in small quantities for artists’ needs (e.g. Madder and Madder Brown).