SUBJECT FORENSIC SCIENCE Paper No. and Title PAPER No. 8: Questioned Document Module No. and Title MODULE No.21: Rubber Stamp and Seals Module Tag FSC_P8_M21 FORENSIC SCIENCE PAPER No.8: Questioned Document MODULE No. 21: Rubber Stamp & Seals TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Stamp and Seal Impression 4. Characteristics of Rubber Stamp and Seal Impression 5. The Examination Process 6. Summary FORENSIC SCIENCE PAPER No.8: Questioned Document MODULE No. 21: Rubber Stamp & Seals 1. Learning Outcomes After studying this module, you shall be able to: Know about the Rubber stamps and Seal Impression. Identify the Characteristics of Rubber Stamps and Seal Impression. Learn about the Examination procedure for analysis of Rubber and Seal impression. 2. Introduction Rubber Stamp Rubber stamping, also called stamping, is a craft in which some type of ink made of dye or pigment is applied to an image or pattern that has been carved, molded, laser engraved or vulcanized, onto a sheet of rubber. The rubber is often mounted onto a more stable object such as a wood, brick or an acrylic block. Increasingly the vulcanized rubber image with an adhesive foam backing is attached to a cling vinyl sheet which allows it to be used with an acrylic handle for support. These cling rubber stamps can be stored in a smaller amount of space and typically cost less than the wood mounted versions. They can also be positioned with a greater amount of accuracy due to the stamper's ability to see through the handle being used. Temporary stamps with simple designs can be carved from a potato. The ink coated rubber stamp is pressed onto any type of medium such that the colored image is transferred to the medium. The medium is generally some type of fabric or paper. Other media used are wood, metal, glass, plastic, rock. High volume batik uses liquid wax instead of ink on a metal stamp. Seal A seal is a device for making an impression in wax, clay, paper, or some other medium, including an embossment on paper, and is also the impression thus made. The original purpose was to authenticate a document, a wrapper for one such as a modern envelope, or the cover of a container or package holding valuables or other objects. The seal-making device is also referred to as the seal matrix or die; the imprint it creates as the seal impression (or, more rarely, the sealing). If the impression is made purely as a relief resulting from the greater pressure on the paper where the high parts of the matrix touch, the seal is known as a dry seal; in other cases ink or another liquid or liquefied medium is used, in another color than the paper. FORENSIC SCIENCE PAPER No.8: Questioned Document MODULE No. 21: Rubber Stamp & Seals In most traditional forms of dry seal the design on the seal matrix is in intaglio (cut below the flat surface) and therefore the design on the impressions made is in relief (raised above the surface). The design on the impression will reverse (be a mirror-image of) that of the matrix, which is especially important when script is included in the design, as it very often is. This will not be the case if paper is embossed from behind, where the matrix and impression read the same way, and both matrix and impression are in relief. However engraved gems were often carved in relief, called cameo in this context, giving a "counter-relief" or intaglio impression when used as seals. The process is essentially that of a mould. Most seals have always given a single impression on an essentially flat surface, but in medieval Europe two-sided seals with two matrices were often used by institutions or rulers (such as towns, bishops and kings) to make two-sided or fully three-dimensional impressions in wax, with a "tag", a piece of ribbon or strip of parchment, running through them. These "pendent" seal impressions dangled below the documents they authenticated, to which the attachment tag was sewn or otherwise attached (single-sided seals were treated in the same way). In the 1982 edition of Scientific Examination of Questioned Documents, Ordway Hilton wrote: “As an office laborsaving device, the hand or impression stamp is convenient to use and useful; as a field of investigation for the document examiner, it is rather infrequent but diversified. Much of its diversity lies in the great variety of stamps in use: those of fixed letter design, those made up entirely of loose type, the facsimile signature stamp, those with rotating sections of the time-date stamp variety, the date stamps with movable strips of type, and any combination of these. The diversity is not limited to classifications based upon makeup. The actual material from which the stamp is constructed and its mode of manufacture adds to the possible varieties.” FORENSIC SCIENCE PAPER No.8: Questioned Document MODULE No. 21: Rubber Stamp & Seals 3. Stamp and Seal Impression Stamp classification is not based on the type of die material, but rather the location of the ink source. Based on the ink source location, there are four main types of conventional stamps encountered by forensic document examiners in their casework: the hand stamp, the self- inking stamp, the pre-inked stamp, and the flat-die stamp. Personal, business, and industrial use rubber stamps are produced by the same manufacturing processes and are classified by the ink source. However, the die materials and inks differ in the industrial setting due to the marking needs of a particular industry. Even though discussion in this text is limited to personal or business use rubber stamps, the forensic document examiner should be aware that other die materials are used in the industrial setting. Personal and business use hand and self- inking stamps contain dies made of vulcanized rubber or photopolymer. The die of a hand stamp is mounted on a die plate attached to a knob handle mount or a molded mount. Because the die is exposed to its surrounding environment, it is subject to damage and debris contamination. Inking of the die is accomplished by manually pressing the die onto the stamp pad in order to obtain ink coverage. The inking process of the hand stamp is achieved manually, while the inking process of the self-inker is achieved mechanically. The self-inking stamp consists of a container (usually plastic) that houses the stamp die and ink pad. Since the die is in a container that usually has a cover, it is protected from excessive debris contamination or cuts and other damage that can occur as a result of colliding with other objects one may find in or on a person’s desk. For inking, the die rotates 180° to press into the ink pad when the top of the container is pressed down. The first two classifications concern dies that primarily use water-based inks. The third classification includes pre-inked stamps characterized by a high relief die and, as a general rule, use oil-based inks. Salt- leached rubber, foam and powder, and premixed gel are the materials used to make high relief pre-inked stamps. The flat-die stamp is the fourth classification, and it has a low- or no- relief die, with the ink pad sandwiched between the die and the die holder. Depending upon their intended use, water- or oil-based inks are used in flat-die stamps. FORENSIC SCIENCE PAPER No.8: Questioned Document MODULE No. 21: Rubber Stamp & Seals 4. Characteristics of Rubber Stamps and Seal Impressions The characteristics a forensic document examiner observes in stamp impressions are influenced by the die material, whether the ink is water based or oil based, the size of the stamp, the type of paper, the interaction of the ink to the paper, and the individual making the impression. The two most common causes of a less-than-perfect stamp impression involve the mechanics of stamping, i.e., failing to hold the stamp correctly, creating an uneven impression, and using too much force when making the impression, causing the stamp to bounce. Differences are observed between impressions made by hand or self-inking stamps and pre- inked stamps. As a general rule, it would be difficult to make a definitive statement as to the type of stamp that made the questioned impression. However, characteristics observed in a stamp impression can provide clues as to the die material of the suspected stamp. Vulcanized rubber and photopolymer are the most common materials used for hand and self-inking stamp dies. These two materials are non-porous and do not retain ink. Whether the material is vulcanized rubber or photopolymer, they share the same characteristics in their impressions, as follows: o Even Ink Coverage o Ring of darker ink outlining the individual letter. Known as the “squeegee effect,” this ring occurs as a result of the relief of the printing area squeezing the ink out to the edge of the ink line. This characteristic is difficult to observe if the entire character is heavily inked. o Absence of an indentation in the ink line. o Rounded beginning and ending of letters. o If water-based ink is used, the bleeding of ink through the paper is minimal. o Ink filling in sharp angles and intersection points of two lines. o Some patchy areas within the inked impression may be observed. o Uneven outline of the letter. Due to its porosity, the die of a pre-inked stamp serves as its own ink reservoir. The materials commonly used for pre-inked dies include pre-mixed gel, salt-leached rubber, and foam and powder.