A Glossary of Embossing Terminology
Definitions of technical terms on this webpage are primarily as the terms are used in the absorbent tissue paper industry. Many of the terms are used with the same meanings in other industries that emboss relatively thin materials in continuous or unbroken lengths.
absorbency (or absorbancy), rate or capacity - A measure of how a material or product picks up and holds a liquid, usually water or oil. The two most important components of absorbency are rate and capacity. The rate of absorption is a measure of how fast a specific amount of liquid penetrates the material. The absorptive capacity is a measure of the quantity of liquid that the material can hold. It is reported either on an area basis (grams of liquid per square meter of product), or on a weight basis (grams of liquid per gram of product). The capacity is very dependent upon how the excess liquid is drained after the product is saturated. Embossing can increase the absorptive capacity of paper and other materials.
anti-nesting - The avoidance of nesting within a roll of product or a stack of product.
anti-ridging - The avoidance of ridging within a roll of product.
appearance - How the embossing looks in the product. In the consumer market, the embossing is often visible through transparent areas of the packaging when the buyer sees the product on the shelf. When the embossing is intended to be a visual “signature” of a branded product, distinctiveness in appearance is important. If the pattern clarity is too weak, irregular, or if the image is not recognizable, then the consumer may see the embossing as not intentional, like water damage, and a sign of poor quality. Sometimes an embossing pattern fails to convey the intended image, and looks more like something else entirely. “It looked like a pillow on the drawing, but more like a pig on the tissue.” Other appearance problems associated with embossing are wrinkles, crushed embossing elements, pattern strike-through (of a nested laminated towel), ridging (or corrugation), and scuffing.
basis weight - Weight per unit area of a paper product. Reported in grams per square meter (gsm) or pounds per ream. Embossing may decrease the basis weight slightly, due to the growth in the machine direction that it may cause.
bath tissue - Also called bathroom tissue, loo paper (in UK), toilet paper, or just TP. Its primary use is to clean and/or dry the skin after eliminating bodily wastes. It is supplied in roll form in most of the world, perforated for easy dispensing. Embossing is used to increase bulk, absorbency, softness, and product roll size.
bulk - A measure of the height of a stack of paper. The number of layers in the stack varies from company to company, as well as what constitutes a single layer. For base paper, one layer usually consists of a single ply of paper. For the finished product, in its final form, one layer may be defined as a unit of product, which may be several plies combined together. Some companies use the term “bulk” to mean thickness divided by basis weight, which is essentially a measure of specific volume. The test result is very dependent upon how much compressive force is applied to the product by the test instrument. Embossing almost always increases bulk, and the effect is greater when a relatively light compressive force is used. Also see thickness and caliper.
CD - Short for cross direction.
commercial market - Also known as Away-From-Home (AFH) market. Manufacture and sale of product for use away from the home. Products are purchased by the case from a catalog, rather than from a display shelf. Storage space is often at a premium. Embossing patterns must be designed to accommodate this (with less emphasis on bulk and roll size).
consumer market - Manufacture and sale of product for use in the home. Most of the volume is sold in grocery stores. Products and packaging must be designed for display on the store shelf, in very direct competition with other brands. Embossing plays a key part in this.
corrugation - See ridging.
converting - A process which reduces a large sized parent roll provided by a paper machine into usable small sized rolls or folded products. The word "converting" may also mean the machinery that applies a converting process, or even the manufacturing area or department where it is done. More information about converting may be found at www.WebconInc.com.
cross direction (CD) - Cross machine direction, which is perpendicular to the direction of the flow of the material that is running through a machine. Almost all of the rollers in the machine have axes that are aligned in the CD. Both cross direction (CD) and machine direction (MD) are in the plane of the material, whereas Z direction (ZD) is perpendicular to the plane of the material.
double-nip embossing - Embossing a multi-ply product with two separate embossing nips in parallel, with one or more plies in each nip, and then bringing all of the plies back together before forming the final product. Bonding the separately embossed plies together can be done with laminating (for a strong bond), or ply bonding (for a weaker bond). The relationship between the positions of the embossing designs in the different sets of plies is called registration. The registrations described in this glossary are nested registration, pin-to-pin registration, and random registration. A configuration where all of the plies pass through a single embossing nip together is called single-nip embossing.
edge embossing - See ply bonding.
element of a pattern - A small feature of an embossing pattern, usually completely surrounded by a region that is at a different elevation. Also called an "embossment". If the element is raised with respect to its surroundings, then it is called male. If the element is recessed with respect to its surroundings, then it is called female. With some embossing patterns, an element may contain smaller elements within it (see spot embossing).
embossing - To change the shape of a thin material or sheet from flat to shaped, so that there are areas that are raised and/or recessed from the rest of the surface, usually without rupturing the material. For an example of embossing that intentionally ruptures the material, see perf-embossing. For continuous embossing of long materials, see rotary embossing. Discontinuous embossing of cut sheets is often done with a stamping process. To learn more about embossing, see the Technology page on this website.
engraver - A company or a machine that does engraving. In the absorbent tissue paper industry, the word is most often used to mean a company which supplies engraved embossing rollers.
engraving - The main process used to create an embossing roller (cylinder) or an embossing plate. Engraving changes the surface from smooth to shaped, either by etching (where material is selectively removed) and/or by mechanical force (like knurling). Etching methods include: chemical (acid or solvent), machining, and laser. Steel embossing rollers are usually engraved with a combination of mechanical pressure and acid etching. Laser engraving is a relatively new process for making embossing rollers and is used to etch a special coating that is applied to a steel roller. For more in-depth information about engraving, and especially about laser engraving, please see the article “Using Laser Engraving in Tissue Embossing” by Carl Ingalls and Ed Giesler, which was presented at CMM International 2003 Conference in Chicago on 15 April 2003.
facial tissue - An absorbent tissue paper product primarily used on the face. There are some people (not in the paper industry) who call it Kleenex® (which is a trademark and brand name owned by Kimberly Clark). Softness is highly valued in facial tissue, and especially in the “ultra premium” category. Embossing on facial tissue can make it feel thicker or plusher and more absorbent. Many facial tissues have special materials added to improve the consumer’s experience of the softness, through a process called lotionizing.
female - When applied to an embossing pattern that is engraved into the surface of an embossing roller or plate, “female” means that the pattern is composed of elements that are recessed into a flat background, like potholes in pavement. A male pattern is composed of elements that are raised up from a flat background, like mesas in a desert. However, many patterns are too complex to be described overall either as male or as female. These terms, male and female, work better when applied to a single embossing element.
finishing - A group of processes which add value by changing the intrinsic properties of the paper after the paper is formed and dried, after all of the papermaking processes have ended. Examples include embossing, calendering, printing, lotionizing, laminating, etc. Most finishing processes are done on converting machines. For more in-depth information about finishing processes, please see the article “Adding Quality Through Finishing Processes” by Carl Ingalls, which was presented at Tissue World Americas 2002 in Miami on 1 October 2002.
handfeel - See softness.
interdigitating embossing - A type of embossing engagement where the raised elements of one engraved roller pass between - but do not surround - similar raised elements of the opposing roller in an embossing nip. Only male elements are able to engage in this way. This is similar to the way that the fingers interlace when clasping hands together, which is the origin of the term “interdigitating”. The most well known and practical application of interdigitating embossing is perf-embossing.
laminating - A process which combines two or more plies of material with a strong bond (stronger than provided by ply bonding), and is used on some paper towel and bath tissue products. Laminating that is combined with embossing in a single unit is often called double-nip embossing laminating. This requires two separate embossing operations that run in parallel (double-nip), an adhesive applicator that places small amounts of glue on the tips of the raised elements of the paper while it is still in contact with one of the embossing rollers, a laminating area between the two embossing rollers where the plies are brought back together again, and a marrying nip (or shoe) where pressure is applied to make the adhesive bond stronger. The two embossing nips are usually rubber-to-steel nips. In bath tissue, the advantage of double-nip lamination is that it provides invisible ply bonding and it also avoids the two-sided handfeel problem that occurs with single-nip embossing. In paper towel, double-nip lamination improves bulk, absorbency (capacity), and roll size. There are several different ways in which the embossing designs on the two embossing rolls are registered with each other and come together in the product. The ones described here are nested registration, pin-to-pin registration, and random registration.
lotionizing - A process which improves the perception of the softness of a paper product by the application of an invisible substance onto its surface. The substance is often an oil, a wax, or a silicone. This is most often applied to facial tissue. One disadvantage is that the lotion can interfere with some ply bonding methods.
male - When applied to an embossing pattern that is engraved into the surface of an embossing roller or plate, “male” means that the pattern is composed of elements that are raised up from a flat background, like mesas in a desert. A female pattern is composed of elements that are recessed into a flat background, like potholes in pavement. However, many patterns are too complex to be described overall either as male or as female. These terms, male and female, work better when applied to a single embossing element.
malleable - Literally, cabable of being worked by hammering, so that the material’s shape can be modified by the application of mechanical force (hammering or pressing) without breakage. This shape change should be permanent. Some materials must be heated to have this property. A more modern term is plasticity.
marrying nip or shoe - The part of the laminating process where the layers to be bonded are pressed together to make the adhesive form a better bond. The best way to do this is to apply pressure only at the glue-bond points, and avoid crushing any other part of the product. In nested lamination, this is done by using a marrying roll that is pressed against the same embossing roller that carried the paper which received the glue from the adhesive applicator. In pin-to-pin lamination, this is done in the laminating nip, which is where the two embossing rollers come into contact with each other. With random registration, it is not possible to avoid crushing unbonded areas of the product.
matched embossing or engraving - An embossing or engraving nip where the surfaces of the two rollers are perfectly matched, so that wherever the surface of one roller is raised by some distance, the corresponding surface on the other roller is recessed by the same distance. When the rollers are fully engaged, there is complete contact between the surfaces of the two embossing rollers at every point along the nip line. In matched embossing, both rollers are engraved (as in steel-to-steel embossing), and one roller is usually made from the other in a matched steel engraving process using acid etching. In actual embossing practice, absolutely perfect matching is often avoided, in order to improve runnability, by creating a small gap between the rollers in selected areas of the pattern. This is also called “mated embossing”.
MD - Short for machine direction.
micro embossing - Embossing with a very fine pattern, sometimes with the purpose of simulating the textured appearance of a TAD product, or for creating a visual impression of a textile fabric. Pattern fineness is often characterized by the density of embossing elements (number of elments per unit area). Micro embossing is sometimes combined with (used as a background) spot embossing and/or quilting.
napkin - See paper napkin.
nested embossing / laminating (registration) - One of several ways in which two layers or plies of embossed product are brought together in a laminating nip for a general process known as double-nip embossing laminating. Nested lamination means that the raised elements of each layer fit between each other in the product, as in interdigitating, so that the tops of each element come into contact with the recessed area (or floor) of the opposing layer. Most laminators run with a significant gap between the engraved embossing rollers to prevent any possible interference between the raised elements. In normal practice, an adhesive glue is applied to the tips of the raised elements of only one of the two layers, and those tips are bonded to the floor of the other layer. Other types of registration for embossing laminating are pin-to-pin registration, and random registration.
nesting inside a roll of product or a stack of product - Nesting is when the embossing elements of one layer of product fit into the embossing elements of the layer above or below it, similar to the way that bowls are stacked on a shelf, which causes them to take up less space. This normally only occurs with single-nip embossing. In a roll product, this usually occurs in alternating bands of nesting and anti-nesting, which is described and illustrated in the article “Using Laser Engraving in Tissue Embossing” by Carl Ingalls and Ed Giesler.
nip - The area where two rollers (cylinders) come into contact, sometimes with pressure. The three most common types of embossing nips are: steel-to-steel (S/S), rubber-to-steel (R/S), and paper-to-steel (P/S).
overall embossing - A type of embossing design with a fairly uniform density of embossing elements, so that there are no significant areas that have no embossing. Usually, all of the elements are identical size and shape. This style of embossing has fallen out of favor in the USA in recent years. Most bath tissue in the US is now embossed with one or more (a combination) of the following types of embossing: quilting, spot embossing, and/or micro embossing.
P/S - Short for paper-to-steel embossing.
paper napkin - An absorbent tissue paper product used with food, and usually provided as a stack of folded sheets. The most common paper napkin product categories are: lunch, luncheon, or family; beverage or cocktail; dinner; and decorative or floral. All of these categories are most often embossed in a single nip. The least expensive lunch napkins may be made with multiple streams of single-ply paper running through the same embossing nip with an overall embossing design, and then the plies that were embossed together are separated into single plies before each ply is quarter-folded and stacked. Dinner napkins are often embossed with a coin-edge plus a decorative border, two or more plies, and many different types of folding patterns. The purpose of embossing on paper napkins is largely decorative, and partly functional (ply bonding and bulk building). Many paper napkins are printed with high quality color printing. Decorative napkins often use edge-to-edge printing, which requires special embossing and ply-bonding considerations.
paper-to-steel (P/S) - Embossing between two rollers where one has a steel surface that is engraved with an embossing pattern, and the other roller is a paper filled roll (made by stacking sheets of paper or similar material on a core, pressing the stack, and machining the surface to be a smooth cylinder). This type of embossing provides finer detail in the embossing design, and some degree of ply bonding. It is the preferred method of embossing for high quality paper napkins. The three main types of embossing nips are: steel-to-steel (S/S), rubber-to-steel (R/S), and paper-to-steel (P/S).
paper towel - An absorbent tissue paper product whose primary use is to absorb liquid, and is most often used to dry hands. It must have very good absorbency capacity, and must remain strong even when wet (a property known as wet strength). The purpose of embossing on paper towel is mostly functional and only partly decorative. Embossing is used to increase the absorbency of paper towels. For the consumer market, embossing is also used to increase the diameter of a roll of product (which is not desired in the Away-From-Home or commercial market).
parent roll - A large roll of paper, also called a jumbo roll, that is unwound into a machine that processes the paper in some way. In the absorbent tissue paper industry, these processes are often called finishing processes. For a multi-ply product, there may be more than one parent roll being unwound into the machine, or the parent roll may have been wound with multiple plies (using a separate rewinding process). In some special cases, the plies are bonded together by some means (see ply bonding) before being wound into the parent roll.
perf-embossing - Embossing by a method that creates a pattern of very small ruptures at precisely controlled locations within the material. This process was invented at Scott Paper Company decades ago and was originally used for ScotTowels® (trademark now owned by Kimberly Clark). Both embossing rollers in perf-embossing are usually engraved with the same pattern of discrete, raised, male elements, and the pattern is designed so that these elements pass between each other when the rollers are engaged in a nip. This is also known as interdigitating embossing.
performance of embossing - The ability of an embossing pattern or machine to deliver the required product properties. It is best determined and documented by a general method called a technology curve.
pin-to-pin embossing / laminating (registration) - One of several ways in which two layers or plies of embossed product are brought together in a laminating nip for a general process known as double-nip embossing laminating. Also known as “tip-to-tip” or “foot-to-foot” or “point-to-point” registration. Pin-to-pin lamination means that the raised elements of each layer contact each other at their tips, which is where the bonding occurs. In normal practice, an adhesive glue is applied to the tips of the raised elements of only one of the two layers. The layers are pressed together in the lamination nip, where the two embossing rollers come into contact. Other versions of embossing laminating are nested registration, and random registration.
ply bonding - A process which causes plies to adhere together, usually rather weakly, so that it is fairly easy to separate the plies without tearing the paper. When the plies are bonded much more tightly, the adhesion process is usually called laminating. Ply bonding is important for bath tissue and for facial tissue whenever either is sold as having two or more plies. The most common ply bonding process uses a set of narrow knurled wheels that are pressed against a smooth anvil roll, and the multiple plies of paper are passed between the wheels and the anvil. This process is often called edge embossing. The very high pressure at the contact points between the knurling and the anvil causes the paper to fuse into glassine at those points. This method of ply bonding causes very visible lines in the product, sometimes negatively described as “railroad tracks”. Embossing two or more plies together in a single nip can also create a weak bond between the plies (the bond is stronger when using a paper-to-steel nip). For bath tissue, the process of perforating the sheets usually creates a weak ply bond at each perf line. Another method of ply bonding applies a small amount of hot-melt glue between the plies, which is completely invisible.
properties of a product or material (also called attributes) - The term physical properties usually means the characteristics of the product that can be measured by a machine (objectively) and reported as a number. For absorbent paper tissue products, these properties include basis weight, bulk or thickness, absorbency, tensile strength, plus the as-packaged properties of roll diameter, roll firmness, stack height, stack firmness, and product weight. These objectively measured properties are approximations of what the user will perceive when experiencing the product. The term consumer perceived properties usually means the characteristics that are better determined by human senses (subjectively). These include appearance and softness (or handfeel), and sometimes fragrance.
quarter-folded - Folding into quarters, by folding in half once along one axis (usually the MD first), and then folding in half once along a perpendicular axis. Most common for paper napkins. Also see folding.
quilting or quilted embossing - A type of embossing design which gives the general impression of a quilt, usually by incorporating pattern features which suggest a network or lattice of continuous or connected stitching lines, and with open areas between the stitch lines that appear to puff up as a quilt often does. Quilting is often combined with spot embossing (a signature boss) and/or micro embossing. Another type of embossing design is overall embossing.
random registration embossing / laminating - One of several ways in which two layers or plies of embossed product are brought together in a laminating nip for a general process known as double-nip embossing laminating. In random registration, also called DERL (for double embossed random lamination), the embossing elements do not engage, and do not even maintain a fixed relationship to each other betweent the two embossing rollers. An adhesive glue is applied to the tips of the raised elements of one of the two layers to be laminated while it is still in contact with its embossing roller. Since registration is random, many of the raised elements of the opposite layer will be crushed in the marrying nip or shoe. Other types of registration for embossing laminating are nested registration, and pin-to-pin registration.
ream - A quantity of paper, measured by area. For fine papers (not intended to be absorbent), one ream is usually 500 sheets. For absorbent tissue papers, one ream can equal 2880 square feet or 3000 square feet, depending upon the company.
ridging - The appearance of a series of circumferential ridges and valleys around a roll of product, where the roll appears to be corrugated like a tin can. The height and spacing of the ridges is very uniform. This is often considered a sign of poor product quality, and is usually caused by the design of the embossing pattern. One solution to this problem is described in the article “Using Laser Engraving in Tissue Embossing” by Carl Ingalls and Ed Giesler.
rotary embossing - Embossing by passing the material between two rotating cylinders that press the embossing pattern into the material. This is the best process for continuous embossing with a seamless pattern.
R/S - Short for rubber-to-steel embossing.
rubber-to-steel (R/S) - Embossing between two rollers where one has a steel surface that is engraved with an embossing pattern, and the other roller has a smooth rubber surface. This term may also be used when the engraved surface is a rigid material other than steel and/or the smooth surface is an elastic material other than rubber. The three main types of embossing nips are: steel-to-steel (S/S), rubber-to-steel (R/S), and paper-to-steel (P/S).
runnability (or runability) - The ability of an embossing process (or any other process on a production machine) to run smoothly at the desired speed with minimum downtime and waste, and with a minimum of attention from the machine operator or from the maintenance department.
single-nip embossing - An embossing configuration where all of the plies that form a unit of product pass together through a single embossing nip. For a one-ply product, the only embossing options are single nip and sequential nip. The double-nip embossing configuration is an option when two or more plies are used.
softness (or handfeel) - The user’s experience of the feel of the material and how it yields to the touch. This is extremely important for premium-quality bath tissue and facial tissue products. Predicting the user’s perception of softness can be done by a machine (objectively) or by human touch (subjectively) using trained testing personel. The machine method is easier and faster, but the human touch method is more accurate, and especially when comparing products that are very different from each other. The components of softness include compressive or pillowy softness, flexibility or drape softness, and surface smoothness. Embossing often improves the first two, but rarely the last. More information can be found at Certified Softness Measurement
spot embossing - A type of embossing design, sometimes called deco embossing. The “spot” is a small discrete region of embossing that is completely surrounded by a much larger area of material that is not embossed at all. The embossing rollers are designed to engage only at the spots, with plenty of space between them at the un-embossed areas. In a rubber-to-steel nip, the spots themselves will appear as male on the engraved roll. However, the embossing elements within those spots may be any combination of male and female. Other types of embossing designs include overall embossing, quilting, and micro embossing. Sometimes, two or more of these types of embossing designs are combined in a single design.
S/S - Short for steel-to-steel embossing.
steel-to-steel (S/S) - Embossing between two rollers where both rollers have steel surfaces, and both are engraved with embossing patterns that are designed to engage each other in some way. One way of engaging the two rollers is matched (or mated) embossing. Another engagement is interdigitating embossing. The term “steel-to-steel” may also be used when one or both of the engraved surfaces is a hard material other than steel. The three main types of embossing nips are: steel-to-steel (S/S), rubber-to-steel (R/S), and paper-to-steel (P/S).
strength - See tensile strength.
TAD - Acronym for Through Air Dried, which is a special tissue papermaking technology that produces desirable lower density for the same strength, resulting in better bulk, absorptive capacity,and softness for the same amount of fiber (basis weight). The TAD fabric that carries the paper through this part of the paper machine leaves a characteristic impression in the tissue paper that looks like very fine and very faint embossing (see micro embossing). This technology is being used on bath tissue and paper towels, but only rarely (if ever) on paper napkins or facial tissue. More conventional tissue papermaking technologies include: Light Dry Crepe (LDC) and Heavy Wet Crepe (HWC). An embossing pattern that works well with one papermaking technology usually does not work as well with a different papermaking technology.
technology curve - A method for determining the entire range of performance of a process. The concept was originally developed by scientists and engineers at Scott Paper Company for use on papermaking processes and technologies. It has been adapted for use on finishing processes, and especially for embossing. For more in-depth information, please see the article “Adding Quality Through Finishing Processes” by Carl Ingalls, which was presented at Tissue World Americas 2002 in Miami on 1 October 2002.
tensile strength - The strength of a material when tested by pulling, in a tensile testing machine. In the absorbent tissue paper industry, this is usually reported as the maximum load that a one-inch (or 25mm) wide specimen will bear before it tears or breaks, and is usually averaged over a number of specimens. The test can be done while the paper is dry or re-wetted (see wet strength). In most products, the test result is very dependent upon which direction the paper is pulled. In paper products, the machine direction tensile strength (MDT) is usually much greater than the cross direction tensile strength (CDT), and the ratio of MDT divided by CDT is called the “tensile ratio”. There are two other measurements that are often provided by the machine that performs the tensile test: stretch and energy. Machine direction stretch (MDS) is important for runnability in converting, and is reported as the percentage of elongation of the test specimen at the moment that peak load occurred.
thickness or caliper - Thickness and caliper may refer to a single layer (one sheet of product or one ply of paper), whereas bulk often refers to a stack of layers. It is difficult to directly measure the thickness or caliper of a single layer of an absorbent tissue paper. The surface is highly irregular, the paper may contain a few small wads or fiber clumps that are thicker than the rest of the paper, and there may be very thin areas or holes. The most common method of measuring the thickness of a material is to place it between two parallel rigid flat plates that are pressed together with a predefined force. The distance between the plates is reported as the thickness or caliper of the material. Note that this method can be very sensitive to a few high points. Also, the test result can be very dependent upon the pressure that is applied to the material by the plates. The increase in the measured thickness before and after embossing is often greater when a lighter compressive force is used.
tissue paper - Paper that is very light in weight. There are two basic categories of tissue paper: wrapping tissue and absorbent tissue. Wrapping tissue paper is stronger, thinner, denser, and less porous than absorbent tissue paper, and is very rarely embossed. Products like bath tissue, facial tissue, paper towel, and paper napkin are made from absorbent tissue paper, and are often embossed to improve their physical properties, appearance, and softness.
toilet paper - See bath tissue.
toilet tissue - See bath tissue.
towel - See paper towel.
wet strength - The strength of a paper product when saturated with water, as determined by tensile testing.
Z direction (ZD) - Perpendicular to the plane of a material, the direction which is thinnest. If the material were placed flat on a horizontal surface, then the Z direction would be vertical. Also see machine direction (MD) and cross direction (CD).