MODULE No.8: Study of Paper

Transcription

1 SUBJECT Paper No. and Title Module No. and Title Module Tag MODULE No.8: Study of paper FSC_P8_M8

2 TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Manufacture of paper 4. Examination of Paper 5. Summary

3 1. Learning Outcomes After studying this module, you shall be able to Know about paper and its manufacturing. Identify different techniques that are employed in the examination of paper. 2. Introduction and scope of paper Paper is one of the important evidence in cases of forgeries and counterfeits. Paper is available in abundance in the market and is one of the most important writing surfaces, so probability of finding different types of paper in different cases of crime related to documents are more. Paper is made by different processes so it can be said that paper can be distinguished from each other on the basis of different papers and it should be done by using scientific methods which provide solid evidence in the detection of paper. Some papers are rough, some are smoother, some are lined, some of them are plain and some have a texture on it. All these varieties of paper provide some sort of uniqueness to them. This uniqueness can be the basis of the identification of paper by different methods that we will reveal in this module moving further with the topic. Paper as mentioned earlier too can be involved in many ways in many cases. These are some examples of cases in which the analysis of paper is of utmost importance for solving the case: - Sometimes the date of the document is not in accordance with the date of the manufacture of the paper; say if a document is available dated to 12 th august 1902 but on analysis of that paper the date of manufacture of paper was found to be of around year Whether the paper is identical with or different from the other papers of the same document. Whether the water mark of the paper is genuine or forged, whether the paper of the questioned receipt, agreement compromise etc. is a part of some other paper from which it has been torn to use the signature or thumb impression appended thereon for some other purpose etc. Paper is made up of a cellulose fiber in the form of compact sheets with uniform thickness.

4 In very ancient time when India was ruled by kings at that time leaves of plant called as Bhojpatra was used for the purpose of writing. Mahatmas and Rishi`s used the sheets of metals for the purpose of writing these metal sheets are known as the Tampatra. Papyrus plant bark was used at around 3500 B.C. for preparation of sheets which could be used for writing. The production techniques has changed with time and the recent discoveries made the process of paper manufacturing easy and less time consuming due to increase in automation. 3. Manufacturing of paper 3.1 Some basic knowledge about paper development and its manufacturing: - The development of mechanical paper by Kelier in the year 1843 has made the paper production easier. The first chemical treatment process using calcium bisulphate got developed in In 1884 a refining process based on the use of sodium sulphate was developed by Dahl. One of the methods of paper manufacturing has already been mentioned in the previous module. There is some more information about how the paper is manufactured.

5 Steps involved in the manufacturing of paper: - Rags of linen or cotton were stored, cut up, washed with water and left to ferment in closed vessels for several weeks until a pulpy mass was obtained This was beaten in oak vats with stamping rods fitted with iron heads and worked either with hand or by primitive mills. The pulp was then spread evenly upon wire moulds, upon which was then placed a mahogany frame termed the deckle and subsequently transferred to a layer of felt. After being repeatedly pressed, it was sized and given final pressing. There are number of substances which can be added to make a paper now a days but for our convenience we categories them as follows: - Rag- this includes cotton, hemp, linen etc. Wood- this include coniferous trees like pine, fir etc. Straw fibers- like rice, wheat, oats, rye etc.

6 The quality of paper can be improved by the addition of some sizing and loading agents which help in developing the cellular strength and required weight of the paper. 3.2 General examination protocols to be followed for the paper examination: The different ways of analyzing the paper and their significance has been mentioned in points given below: - Colour of the paper should be determined by comparing it from the colour chart. Weight- the weight of the paper should be confirmed per square meter. For common paper the weight is approximately gram/sq. meter. There can be a difference in the limit of 2.5% only for the samples which have the common origin. Thickness-the thickness of the paper can be measured by the micrometer and paper calipers. Ash residue- cellulose, cotton, jute, sun and deciduous fibers composed paper have a ash residue of 0.4 to 1.5%pulp of straws and cellulose made paper have a ash residue of 2 to 6% and for rice paper this weight is 14 to 15%. The papers which have the common origin may have a difference of up to 4.5%. the ash residue is mostly due to the presence of loading agents. Microscopic examination: - the ratio of fibers and the distribution of these fibers throughout the paper is same in the papers of same batch. From Microscopic study of paper we can also know about the structure of fibers present in the paper. Character of paper: - it can be determined by the degree of beating and the study of the amount of the fibers. Fluorescence: - two papers can be compared under ultraviolet light for the comparison of fluorescence. Water mark: - watermark can be seen in strong light. The size of watermark, its design, and the fluorescence it produces in the UV light. Loading and sizing agents: - sizing agents like rosin, starch, gelatin, aluminium hydroxide and synthetic polymers can be used to stop feathering of ink in the paper and hence they can be detected by careful examination of the paper. Sizing agents are also used to provide cellular strength to the paper. Loading agents are used to make paper smoother, and non-transparent. They are also known as the fillers.

7 Coloring matter: - if the paper have been coloured by using some dye or pigment then the paper can be subjected to TLC for the detection of that particular dye or pigment. Other evidences like fingerprints can also be found on the documents many times so before doing anything on the document it is checked for any other evidences like fingerprints and then preserved accordingly. 4. Some other examinations which are more specific Appearance of paper is an important factor in examination or study of paper it includes following important points and should be done while analyzing document by physical method: - All the markings on the paper should be recorded and also the location of these marks should be noticed. The marks which should be noticed include marks like punch marks, staple marks, indentations etc. The edges of the paper should also be examined carefully either with a low power microscope or with a magnifying glass to determine if there are any torn edges or cut edges in the paper. The dimensions of the paper should also be noticed. The surface texture of the paper under analysis should also be studied carefully. The number and the positions of folds present if any should be noticed. The watermark identification is also one of the important aspects of the paper study as it can also be forged. The following knowledge can prove good for distinguishing artificial watermark from the genuine one: - In artificial watermark the paper will not be thinner in the area of watermark because the thinning of watermark can only be caused in the paper at the time of its manufacturing. Sometimes an artificial watermark is made by applying some acid in the appropriate area to make the paper comparatively thinner and sometimes a watermark is made by applying some oil or grease on a metal block and pressing it against the paper to make it comparatively more translucent.

8 In the latter case, the forgery may be detected by treating the watermark area with dilute caustic solution which would obliterate or dim the artificial/fake watermark. Identification of the fibers present in the paper pulp: - the identification of the paper pulp can be done by its microscopic examination and the conclusion can be drawn on the basis of in-depth study of the fibers present and the study should be done by an experienced scientist. The fragment of paper under analysis should be treated with 1% of sodium hydroxide; this is done by separation of the fibers of the paper. Once the fibers get separated they are placed on the slide and then a small drop of Herzberg`s reagent is added to it. This prepares the fibers on the slide for microscopic examination. The following fibers are generally used in the paper industry: - Wood fibers- they are found in coniferous trees like pine or they can also be obtained from the deciduous trees such as eucalyptus, chestnut etc. the fibers of the wood fiber are shorter than the fibers of the textile fibers and they have a broad lamina with a wider circular orifices surrounded by bordered pits. Textile fibers-these fibers are generally obtained from plants like flax, hemp and cotton etc. their fibers are very long and they have very narrow lumen. Starch fibers- they are a product of plants such as rice, wheat, oats and rye etc. their fibers have hair or scale like epidermal cells and cylindrical or spherical parenchyma cells. There fibers are smaller and slenderer. Detection of the sizing agents: - as many sizing agents are added to the paper for different purposes so, their detection may help us to identify the paper involved in crime. There are some of the methods which can be used to detect some of the sizing agents present in the paper. These methods are given below: -

9 Gelatin which is one of the sizing agents in the paper can be identified by a chemical reaction. Boil some paper strips in water and save the extract Extract is treated with dilute solution of gallotanic acid Gelatin in the presence of gallotanic acid gives rise to flocculent yellowish precipitate. Rosin is also one of the sizing agents which can be detected in the paper as follows: - One to two drops of saturated solution of sucrose is added to a small piece of paper placed in a porcelain tile. After ten seconds the excess solution is removed from filter paper and one drop of concentrated sulphuric acid is added to it, if red raspberry colour appears then rosin is present. If gelatin is absent in the paper then casein can be identified by using Millon`s reagent which is a solution of mercury in its own weight of fuming nitric acid and then it is diluted with two parts of water. The production of pink colour indicates casein is present. Starch can also be detected in the paper by the formation of characteristic blue colour with a dilute solution of iodine.

10 5. Summary Paper is one of the important evidence in cases of forgeries and counterfeits. Paper is available in abundance in the market and is one of the most important writing surfaces, so probability of finding different types of paper in different cases of crime related to documents are more. The paper are made by different process so it can be said that the paper can be distinguished from each other on the basis of different papers and it should be done by using scientific methods which provide a solid evidence in the detection of paper. Some papers are rough, some are smoother, some are lined, some of them are plain and some have a texture on it. The development of mechanical paper by Kelier in the year 1843 has made the paper production easier. The first chemical treatment process using calcium bi-sulphate got developed in In 1884 a refining process based on the use of sodium sulphate was developed by Dahl. The quality of paper can be improved by the addition of some sizing and loading agents which help in developing the cellular strength and required weight of the paper. General examination protocols to be followed for the paper examination that is what are the different ways of analyzing the paper and their significance has been mentioned in points given below: - Colour. Weight. Ash residue Microscopic examination. Loading and sizing agents. Coloring matter. Fluorescence. Thickness etc.