R. W. Sindall

“ The complete examination of an art paper, apart from the practical test of printing, involves the determination of the amount of coating matter added to the paper, the proportion of glue in the coating, and the usual analysis of the paper itself. ”

“ The Chinese were not only the inventors of felted paper and the imitators of rag paper—though in the preparation of the latter they made use of rags only as a surrogate by the side of raw fibres—but they must also be credited with being the forerunners of the modern method of preparing ‘cellulose paper.’ For their very ancient practice of extracting the fibre from the bark and other parts of plants by means of maceration is in principle identical with the modern method of extracting ‘cellulose’ by means of certain chemical processes. ”

“ A paper in its normal condition always contains a certain proportion of water as one of its ingredients, and the presence of this moisture has much to do with the strength, elasticity, and use of the paper, the absence of moisture giving rise to defects and troubles in the use of the paper which to a certain extent lower its commercial value and deteriorate it, though not perhaps in the sense of permanent degradation of quality. ”

“ Boil the paper with a mixture of alcohol and sulphate of alumina. If no dye is extracted or a fluorescent solution is formed, we have an inorganic pigment, or eosine, phloxine, rhodamine, safranine, or one of their allies. Add bleaching powder solution, and heat. If the paper is bleached, add concentrated hydrochloric acid. A violet colour shows safranine or an analogue. If there is no colour, but the fluorescence disappears, we have eosine, phloxine, rhodamine, or one of their allies. If the paper is not bleached test for inorganic colouring matters. ”

“ In the case of common printings and writings, which form the great bulk of the paper made, the possibility of one mill competing against another, apart from the important factor of the cost of freight, coal, and labour, is almost entirely determined by the economy resulting from the introduction of modern machinery. ”

“ Pure air has little or no action upon paper, cellulose being a remarkably inert substance, and even in impure mechanical wood pulp, if merely exposed to pure dry air, the signs of decay would be delayed considerably. The combined action of air and moisture is of a more vigorous character in promoting oxidation changes in the fibres, or a dissociation of the sizing and other chemical ingredients of the paper. ”

“ The manufacture of parchment paper is an example of the practical utility of the chemical reaction between cellulose and acid. A sheet of paper is dipped into a mixture of three parts of strong sulphuric acid and one part of water, when it becomes transparent. Left in the solution it dissolves, but if taken out and dipped into water in order to wash off the acid the reaction is stopped, and a tough semi-transparent piece of parchment is obtained. The cellulose is more or less hydrated, having the composition
C12H20O10 H2O,
a substance having the name amyloid. ”

“ Colour.—If the subject of deterioration of paper is to be considered in its broadest sense as including changes of any kind, the fading of colour must be taken into account. The use of aniline dyes which are not fast to light results in a loss of colour in paper just as with textiles, and the fading may be regarded as a function of the dye and not as arising from its combination with the paper. ”

“ The preparation of a small quantity of cellulose from materials like straw, rope, hemp, the stringy bark of garden shrubs, wood, and bamboo can easily be accomplished without special appliances. Soft materials, such as straw and hemp, are cut up into short pieces, hard substances like wood and bamboo are thoroughly hammered out, in order to secure a fine subdivision of the mass. The fibre so prepared is then placed in a small iron saucepan, and covered with a solution made up of ten parts of caustic soda and 100 parts of water. ”

“ The questions relating to the chemical residues of paper [Pg 239] can only be adequately dealt with by a discussion of actual cases which arise from time to time. There are certain conditions in manufacture, common to all papers, which may give rise to the presence of chemical residues, of which two have already been mentioned.
The acidity of papers is frequently quoted as an instance. It is true that the presence of free acid in a paper is most undesirable, as it seriously attacks the cellulose, converting it into an oxidised form. ”

“ It is sometimes argued that the lack of durability is due to the want of care on the part of manufacturers in preserving the knowledge of paper-making as handed down by the early pioneers, but such an argument is superficial and utterly erroneous. The quality of paper, in common with the quality of many other articles of commerce, has suffered because the demand for a really good high-class material is so small. ”

“ The plant grows to a height of three or four feet, and when mature the long blades of grass curl up into the form of a cylinder resembling a piece of wire. The leaf consists of two parts, the stalk and a sheath, which are easily separated when harvested. The grass is pulled up by hand and stacked into heaps in order that it may be dried by the heat of the sun, after which process it is carefully picked over for the removal of all extraneous matter and impurities. It is then graded, the best sorts being kept for weaving, and the remainder being sold for paper-making. ”

“ Introduction.—The process of beating has for its object the complete breaking down of the bleached pulp to the condition of single fibres, and the further reduction of the fibres, when necessary, into smaller pieces. The disintegration of the material is essential for the production of a close even sheet of paper, and the amount of beating required varies greatly according to the nature of the raw material, and the class of paper to be produced. ”

“ The gradual fading of some dyes, however, and of many water-colour pigments may be traced to the presence of residual chemicals in the paper and to the presence of moisture in an atmosphere impregnated with gaseous or suspended impurities. In fact the latter is a greater enemy to permanence of colour than light, since it has been proved by experiment that most colours do not fade when exposed to light in a vacuum. The oxygen of the air in combination with the moisture present is the principal agent in bringing about such changes. ”

“ Parchment.—Parchment succeeded papyrus as an excellent writing material, being devised as a substitute for the latter by the inhabitants of Pergamus on account of the prohibited exportation of Egyptian papyrus. For many centuries parchment held a foremost place amongst the available materials serving the purpose of paper, and even to-day it is used for important legal documents. This parchment was made from the skins of sheep and goats, which were first steeped in lime pits, and then scraped. ”

“ Now the conditions of boiling may be varied by altering one or more of these factors, the period of boiling, the strength of solution, or the steam pressure, and the paper-maker must exercise his judgment in fixing the exact relation between the varying factors so as to produce the best results.
In the second place, the mechanical devices for washing the boiled pulp and for bleaching cause slight losses of fibre, which cannot be altogether avoided when operations are conducted on a large scale. ”

“ Careful attention is paid to economy of every kind with regard to the power required for driving the machine, the amount of steam consumed in drying the paper, recovery of excess of fibre and china clay which escapes from the machine wire, and similar details of a mechanical order. ”

“ Test for Esparto in Papers.—Paper containing esparto fibre may be tested by means of a weak solution of aniline sulphate. The suspected paper is gently heated in the test reagent, and if esparto is present the paper turns a rose-red or pink colour, the depth of colour being a measure of the amount of esparto. Most of the modern book papers are prepared from chemical wood pulp and esparto mixed in varying proportions, and while this test can be used as a means of detecting a small or a large proportion of esparto, a microscopical examination is required for a more accurate estimation. ”

“ In the manufacture of newspaper the tendency during recent years has been to make the paper mill operations as mechanical as possible and to dispense with the preliminary operations which are essential for the manufacture of half-stuff, the chemical processes being left in the hands of the pulp manufacturers.
The manufacture of straw cellulose is now practically confined to Germany, but small quantities of the bleached straw cellulose are imported because the pulp imparts certain qualities to paper which improve it, notably in making cheap printing papers harder and more opaque. ”

“ The presence of iron is undesirable, particularly in photographic papers, and since cellulose has a remarkable affinity for iron, the conditions of manufacture which tend to leave iron in the pulp have to be taken into consideration. The presence of minute quantities of iron in the form of impurities must not be confused with the presence of iron in large quantities derived from the toning and colouring of paper by means of iron salts.
The fading of colour is frequently observed when coloured papers are tested on boxboards, particularly those made of straw. ”

“ For the best quality of straw cellulose, the material is cut up into small pieces by machines which resemble an ordinary chaff-cutter, and the knots taken out by a separating machine. In most cases, however, the whole straw is simply cut up into small lengths of about one to two inches long, and placed at once in the digester. When the straw is contaminated with foreign weeds, sand, husks, and similar substances, as is usually the case, it is carefully hand-picked by girls, who remove these impurities, which tend to produce particles of unbleached matter in the finished pulp. ”

“ In fact, the well-known differences between the raw materials used for paper-making, and also between the numerous varieties of finished paper, are to be largely accounted for and explained by a careful study of the cellulose group, particularly with reference to the microscopic characteristics and the chemical composition of the individual species.
The only vegetable substance which may be regarded as [Pg 22] a simple cellulose is cotton, all others being compound celluloses of varying constitution, the nature of which cannot be appreciated without a considerable knowledge of chemistry. ”