One of the important tasks of the forger is to find a suitable paper upon which the document is to be forged and one of the daunting tasks of the question document examiner is Forensic Analysis of Paper or Paper Examination or Study of paper.
The need to examine a paper arises when a document is suspected or questioned to be forged. It is very often seen in wills suspected to be forged , counterfeit currencies, notarised documents, registry of property etc.
Some questions that a Questioned Document Examiner needs to answer regarding paper analysis are :
- Whether the questioned paper is identical with or different from the other papers of the same.
- Whether the questioned paper is identical with the source of the document i.e. same origin
- Whether the water mark of the paper is genuine or forged.
- whether the paper of the questioned document is a part of some other paper i.e. multiple origin.
- Sometimes he needs to comment on the age of paper too.
Let us now read in brief history of paper and what all features are observed while a QD expert is assigned paper examination. In this post , we will be taking you briefly around the process of paper manufacturing.
Paper
Ever since paper was found in India being made from cotton and used as a writing medium in 327 B.C., many more attributes have been invested to it by newer raw materials and improved techniques of manufacture. It is now a very complex material, practically beyond the scope of a concise and precise definition. It is an amassing network of fibres having as much a 75% air space only a small percentage of which may be inside the fibres, the rest being in the form of pores or voids enmeshed by fibres, or recesses on the surfaces.
The fibres may be natural or synthetic, and they may be intrameshed by being deposited from a suspension in liquid, gas or vapour. The appearance , strength and other properties of paper are determined by the quality of fibres, formation of the meshwork, strength of inter-fibre bonds, use of certain chemicals or additives, and the treatment given during or after the process of manufacture.
Raw Materials
The bulk of paper is made from vegetable fibres however fibres may be derived from various other sources such as wool, silk, asbestos, nylons, etc. Cotton is considered to be an ideal raw material for paper manufacturing because of its colour, purity with durability, folding strength but as the price is very high only the secondary cotton fibers in the form of rags, tailor cuttings, hosiery cuttings, and the like, are actually used for manufacture of quality papers.
Bast fibres like linen, hemp, and jute are also available to paper makers in the form of rags, old mats, ropes,etc., and constitute raw materials for speciality papers. Ordinary papers used for writing and printing are made from grasses, bamboos, and agricultural residues like straw, bagasse and jute-sticks.
Paper Making Process
1.Raw Material is chosen to make the paper.
2.Cutter: it is used to convert raw material into small pieces called wood chips. Wood is stripped of its bark and process is done with water or without water.
3.Pulp Making: wood is composed of cellulose fibres that are bounded together with a substance called lignin. Depending upon the quality of paper required, one out of the two following process is used: (a) Mechanical Pulping and (b) chemical Pulping.
Mechanical Pulping: It is done by crushing the stripped logs with grinders and soaking them with water. The wood chips are heated in a digester using steam at high temperature and pressure and pulp prepared from this process is known as thermo mechanical pulp (TMP). The output paper from this process is of poor quality that is less strength in paper. Paper is used for news printing and paper boards.
Chemical Pulping: when chemical like sulphate is used in digester along with steam at high temperature and pressure, the pulp prepared through this process is known as Chemithermo mechanical pulp (CTMP). Chemical pulp is also known as Kraft pulp. This type of paper is available in the market in the form of packing paper and brown paper (unbleached).
The chemicals used are (1) sulfite salts with an excess of sulfur dioxide and (2) caustic soda and sodium sulfide (the kraft process).
Digester:
(a) Stationary Digester:
Temperature: 160-170o C
Pressure: 10kg/cm2
Time duration: 3 hrs
Yield: 60-80%
Wood chips + Water + Caustic Soda + Sodium Sulphate
(b) Rotary Digester:
Generally it is used for fibres of Bagasse, Wheat and rice Straw etc.
Yield: 45-60%
4. Washing: Washing is done using water to remove chemicals and lignin from the pulp.
5. Screening: This process removes the over-sized fibres.
6. Bleaching: Chlorine dioxide, hydrogen peroxide etc. are bleaching agents. Oxygen bleaching is the latest technique. Bleaching gives whiteness, more resistance and absorbent to the paper.
7. Sheeting and Drying: the pulp is fed to rotatory screen and goes to head box. Head box controls the GSM of the paper. The pulp at this stage contains very high water content (over 90%). A canvas or belt with vacuum suction system serves to extract excess water from the pulp. The system is called press section. During this process 60% of water is drained off.
Woollen belt carries paper from first press section to second, the Dryer Section. Here, the paper is heated through steam at 70 – 80oC.
8. Calendaring: The steel cylinders are used to compress the paper to smooth the surface of the sheet.
9. Winder: At this time, a winder is used to rolls the sheet.
10. Cutter: It cuts the sheets in required size.
Pigments/ Fillers/ Additives used in Paper
Paper used for writing or printing usually contains white pigments or fillers to increase brightness, opacity, and surface smoothness, and to improve ink receptivity. Clay is commonly used as a filler in paper. Another pigment is titanium dioxide (TiO2), it is the most expensive of the common pigments and is often used in admixture with others.
Calcium carbonate is also used as a filler to impart improved brightness, opacity, and ink receptivity.
Other fillers are zinc oxide, zinc sulfide, hydrated silica, calcium sulfate, hydrated alumina, talc, barium sulfate, and asbestos.
The most common way to impart colour to paper is to add soluble dyes or coloured pigment to the paper .
Starch, polyacrylamide resins, and natural gums are used to increase the dry strength of paper.
Forensic Analysis of Paper
It is done by:
- Physical examination
- Chemical examination
- Microscopic examination
Physical examination:
Physical examination of paper involves the examination of paper by merely looking at the paper via the naked eyes. Here, we examine the:
- Colour- The colour of the paper is compared with the other documents in question or with the standard document (if available). The changes in colour of the paper due to storing conditions, reactions of the environment, yellowing of paper naturally or artificially is also observed.
- Condition – The condition of paper is determined by the environmental conditions in which it is being stored. The paper stored in safe inside a book case will be in much better condition as compared to that which is kept in a open or damp place. The deterioration in the condition of paper depends on the amount of light to which they are exposed, moisture, wind, temperature, etc. conditions.
- Dimensions – The papers available in the market are of standard size/dimensions (length, breadth/width, diameter, GSM), whose data is readily available with the manufactures. If the expert is able identify the make and model of the paper under question then its dimensions can be compared with the standard dimensions. Also the papers of the document under question should be compared with each other to give an idea of any torn/removal of paper portion from the original paper.
- Appearance – Texture, colour, dimension, transparency, staple holes, pin holes, grease and folds, indentation marks, printing and writing. These features are observed in the questioned document and any discrepancy if seen is made note of.
- Staple marks – The number, shape, depth, position etc. of the staple marks are well observed and examined carefully. This proves/ help in identifying any substitution of paper made.
- Fold –The fold (if present) are carefully observed under the stereomicroscope to check if a fold has been done before writing on it or vice versa. This observation makes it possible to gain the knowledge whether the writing is made on the fold or under the fold. Also the number and depth/prominence of fold marks help us in identifying the substitution made, if any.
- Florescence – Some papers shows specific florescence under UV-light which adds on to their safety and uniqueness, which is helpful identifying and authenticating such papers.
- Watermarks –It is an important physical characteristic which help in comparison and dating of paper.
Chemical examination:
Chemical examination of paper is done to estimate the presence of various components like starch, glue, clay, titanium oxide or paraffin wax etc. Also to determine the specific dyes used. The type of bleaching agent added.
1.Dye examination: it is done by using specific chemical reagents to test the presence or absence of a specific dye. The reagents used are dye specific and target the trace elements present in the dye.
2.Glazing material:it is done by micro-chemical analysis for the examination of glue, starch, or any other gelatinous matter.
3.Ash Determination: Questioned document and control sample both are carried upon a flame and the colour of flame, weight of ash, smell of gases released, etc. is carefully observed.
Microscopic examination:
Microscopic examination involves the use of various types of microscopes and state-of-the-art equipments.
- Colour examination: it is done by visual observation, under UV light of short wavelength (254nm) or in longer wavelength (366nm).
- Trace elemental analysis: it may be possible that many trace elements are present in small quantity on the paper. It can be done through Neutron activation analysis (NAA), Atomic absorption and emission spectroscopy, energy dispersive analysis.
- Fibre analysis: it is possible for papers to have same water marks and other physical characteristics but still have entirely different fibre and chemical composition. In fibre analysis, one has to establish the type of fibre like cotton, wood or synthetic, etc. it is primarily done through microscopic examination and observing the morphological characteristics of fibre.
In our next post we will take up examination of fibres in detail as it is one of the most important topic for entrance and semester exams. Happy Reading 🙂
Nicely explained. Thank you for clearing all my doubts