Paper

Paper, a dense felt made from crushed plant fibers, which has been formed into thin sheets of various sizes and colors. Paper is used for printing, writing, drawing, drafting, wrapping, as wallpaper, etc. In the sanitary evaluation of paper intended for writing and printing, the following factors are taken into account: 1) the size of the printing paper sheet, 2) the weight of the paper, 3) its surface, 4) color shade, 5) strength, 6) thickness, 7) admixture of wood pulp, and 8) transparency. Paper should be white or slightly yellowish, even, smooth, without gloss, with a low wood pulp content, and of such thickness that the print or writing does not show through from the reverse side. The dimensions of a printing paper sheet are indicated by its length and width in the form of two multipliers. The weight of paper is determined on special balances (quadrants) by Shopper by weighing one sheet; the pointer on the balance shows in kilograms the weight of a ream, which contains 480 and 500 sheets; accordingly, there are two scales on the balance scale. Depending on the character of its surface, paper can be clean, dirty, smooth, rough, even, uneven, without gloss, with slight or strong gloss. From a hygienic point of view, glossiness is important, as it has the ability to dazzle, and printing on such paper is difficult to read. Therefore, only a low degree of glossiness is permitted. The whiteness of paper is determined by standard samples, which are designated by ten numbers: 1-9 with an intermediate number between 6 and 7, number 67s. Good paper should be completely white, without any shade, and should not yellow with time. The strength of paper is tested by special devices for tearing, extensibility, and brittleness. The thickness of paper is determined with a micrometer; for accuracy, 3 to 5 sheets should be placed; the results are recorded as a fraction: numerator - micrometer readings, denominator - number of sheets placed; division determines the average thickness. The thickness of paper is determined insofar as it affects transparency. Paper should not be thinner than 0.075 mm. The determination of wood pulp admixture is based on the staining of wood with reagents of a certain color. Qualitative reactions: 1) 20% aqueous sulfuric aniline stains paper with wood pulp yellow; 2) alcoholic solution of orcinol - dark violet color; 3) resorcinol in alcohol with hydrochloric acid - blue-violet color. Quantitative determination: 1) according to the color table of Klemm with Wiesner's reagent: 1 g of phloroglucinol, dissolved in strong alcohol, diluted to 50 cubic cm with water and 25 cubic cm of strong HCl added to the solution; 2) according to the color scale of Wurster with reagent or reagent paper (both available ready-made) - also red staining. The percentage content of wood is determined by comparing colors with a color scale. The presence of wood affects the strength, transparency, and yellowing of paper. The permissible standard is not more than 10% wood. The transparency of paper is examined by Klemm's diaphanometer, in which paper is tested for light absorption of a normal candle: one unit divided by the number of sheets that absorbed the light of a normal candle gives the value of absolute opacity; the norm is Vis. The hygienic significance of paper is especially important for textbooks, research in various countries having shown unsatisfactory quality of paper. The hygienic importance of paper quality for textbooks was recognized long ago and found reflection in the relevant legislation of different countries. The Württemberg regulation of 1678 is the oldest official document regarding the use of good paper for textbooks; in Germany in 1746, the first decree was issued prohibiting the use of poor paper. In Russia in 1905, standards and rules for sanitary control of textbooks and teaching aids were approved by the Ministry of Public Education, which were to come into force for all newly printed non-stereotyped editions after 6 months, and for stereotyped editions after 5 years. - According to Nikitin's research in 1906, the following results were obtained: paper thickness below norm - 76.4%, paper with gloss - 78%, print transparency - 84%, wood pulp content above norm - 70%; of the 20 textbooks examined by Ya. S. Shapiro and I. L. Freydgeym in 1926, only one met the hygienic requirements, having only one defect: not quite sufficient paper thickness; the other 19 books had one or other significant defects from a hygienic point of view. As for paper used for wrapping, especially food products, as well as for replacing napkins ( in public canteens) and for other everyday purposes, sanitary requirements boil down to the fact that for these purposes clean, unused paper of appropriate strength and softness depending on the purpose, and uncolored (especially, with harmful dyes that transfer to food products) should be used. As for paper wallpaper, sanitary requirements require that it be, if possible, light-colored (not absorbing much light), not rough (to avoid dust settling on it), air-permeable (not hindering natural ventilation), easily cleanable, and not contain harmful substances and dyes, e.g., arsenic (see Wallpaper).