Technical Terms

ADDITIVE. Substance that is added to an ink to change its initial properties.

CAPILLARY FILM. Sheet of pre-sensitized emulsion which adheres to the mesh with water and after the excess water is removed with the help of a squeegee, is dried and then later, developed.

CATALYST. Chemical product that makes it possible to accelerate or complete the polymerization of a compound.

COVERAGE. Ability of an ink to cover or superimpose its own color over that on which it has been printed.

CURER. Generic name by which additives for improving washing resistance of water based textile inks, are known. Normally, they are compounds based on urea-formaldehyde resins.

DEGREASING. Removal of grease material before fabricating the screen frame. Degreasing will help to improve the curing of the screen emulsion.

DIAZO. A photosensitive chemical or process by which screen printing emulsions are made sensitive to actinic light; characterized by its controlled definition, low toxicity and useful life.

DISPERSION. A uniform suspension of fine, solid materials in a liquid medium.

DPI. : Dots per inch (abbreviation of the Letters). It refers to the definition of digital or computer printing (arranged).

DUROMETER. A measurement of the hardness of a material, that is, it’s resistance to permanent indentation. In screen printing, this term is used to define the hardness of the squeegee rubber typically made with silicone rubber. Dual or multiple DUROMETER is used when the squeegee rubber is made with different rubber compositions to get multiple end performance parameters.

FISHEYE. A flaw in an emulsion coated screen that results in a generally circular thinning defect of points in the emulsion film, which are the result of dust on the screen fabric, insufficient degreasing of the screen or insufficient emulsion sensitizer mixture.

FRAME. Frame support for silk screen printing It is understood to be fabricated from finished tubing, which has the function of subjecting the fabric to a strong tension. The frame must resist mechanical deformation whilst forming the screen and during the printing process, insofar as it is possible. It must withstand the chemical agents and maintain good dimensional stability. It may be made of wood, metal, aluminum or steel. There is also a “Retensionable” type”.

FIBRILLATION. Fibrillation in screen printing is when the fibers of a fabric stick through the ink deposit, giving a faded or even hairy look of the fabric surface.

GHOST IMAGE. Vague image of the design which remains on the screen mesh after having been reclaimed.

HALF-TONE OR “NETWORK”. Image in which different tones are obtained by dots of different sizes and concentrations according to the amount of light or shade of the areas represented.

HEAT CURING. Application of heat to textile printing to obtain polymerization of the ink. Its parameters are temperature and time.

LPI. Lines per inch. Lines formed by rows of dots on an original, a film or a print. The number of lines in one inch are counted.

MATRIX. Image recorded on a screen by means of a photolith, which enables the passage through it, of the silkscreen inks, it comprises two zones: printed and unprinted.

MIGRATION. The movement of ink into another ink, coating, or substrate causing unwanted color change, caused by a reaction between the ink and the fabric dyes, or could be from the fabric fibers to the printing or from the printing to the fibers. This phenomenon also occurs between coats of different inks.

MISREGISTRATION. An incorrectly positioned image during printing or finishing; or the failure to be properly registered, one color imprint to another.

MOIRÉ. An undesirable optical pattern that occurs when one regular set of parallel lines or dots crosses another set, at various angles of intersection or by the regular pattern of mesh threads intersecting the halftone screen pattern. This problem is more acute when the number of threads per cm of the mesh is a multiple of the number of dots per cm of the half-tone network. There is a series of methods for reducing this problem.

OPACITY. Optical density of a material, generally a pigment, as opposed to transparency. An ink with high opacity is said to have good covering power which means its ability to cover or superimpose itself on the base color to which it is applied.

PHOTOGRAPHIC EMULSION. Product which, on being mixed with a sensitizer, will be used for recovering and recording screens by the direct die-cast method.

PHOTOLITH. Transparent material containing the graphic that serves for the preparation of silk screening frames. It must be prepared directly, that is to say looking from above the emulsified side. The photoliths may be manual, photographic or digital. The sheets on which it is made must be the most transparent possible.

PIGMENTS. Substances with high coloration, finely ground of organic or inorganic nature use to impart color to the inks.

POLYMERIZATION. Chemical reaction ,initiated by a catalyst, heat or light, consisting of the chemical union of two or more molecules, to form bigger and more complex molecules, obtaining a compound with improved characteristics of cohesion, adhesion, stability and resistance.

PREDRYING. Partial drying of a printing before printing the next color or total drying.

PRESSURE. The amount of vertical force required to pass the ink from the screen mesh to the support.

4COLOR/QUADRA COLOR (QUADRA-CHROMIC). Reproduction process using dots that, using only four colors (cyan, yellow, magenta, and black), succeeds in printing the optical illusion of possessing all other colors in the spectrum.

RECLAIMING. (1) The process of removing the emulsion, ink and stencil from the screen mesh after a printing in order to obtain a clean screen for preparing another screen mesh. (2) The process of cleaning used solvent to obtain a reusable product.

RECLAIMING SOLUTION. Liquid chemical product, gel or paste used to remove a screen printing film or emulsion from screen mesh to make the mesh useful again.

SAWTOOTH. A stairstep appearance on the edges of a screen print; the effect of stencil material that conforms to the threads of a screen printing mesh rather than the contours of the design on the film positive from which the stencil is produced. The main reason: the coat is too thin. To avoid this, it is recommended to use a multiple damp, over-damp emulsifier or after drying, emulsify once again on the frame print face.

SCREEN. This is the combination of a screen mesh and its tensioning support frame.

SHADING EFFECT. Gradual variation of hue or tone of a printing, obtained by adding dots on an otherwise transparent sheet until obtaining another color. The mixing of different colored inks to achieve a gradual lightening of color is known as stumping.

SHORE HARDNESS. An international scale for measuring the indentation hardness of the material as determined by tests made with a durometer gauge or scleroscope. (Consists of a ball for deflection or pin point for depression into the material, which is at least 100 mils thick – Instrument manufactured by Shore Instrument Manufacturing Co., Jamaica, New York USA). The hardness of squeegee blades is measured in Degrees Shore. A higher number indicates greater hardness. The hardness recommended in serigraphy is generally 60D- 80D Shore.

SCREEN MESH. Technical fabrics made of polyester or nylon fibers. Polyester meshes, which are less elastic, are used for printing on flat or cylindrical surfaces whilst those of nylon, that have good elasticity, are recommended for printing on uneven surfaces.

SQUEEGEE. Instrument consisting of a wooden or metal support with a flexible rubber blade used to force ink through the openings of a screen printing stencil when in contact with a substrate. The edge, pressure, angle, material, as well as the hardness, all contribute to producing a good final print.

SQUEEGEE ANGLE. Angle between the squeegee and the screen frame which helps to control the amount of ink forced through the screen. The usual angle is 75°.

SUBLIMATION. Process where dye pigments change from solid to vapor without passing the liquid state and back to solid again with the application of heat. In textile printing, the technique of sublimation consists of printing on paper with sublimation ink (Sublisol, Subliset or Pgm Subli) and then transferring it by applying pressure and heat (190-210 °C) for one minute. Printing by sublimation is only possible on polyester, lycras®, acetates and mixtures of cotton with a high percentage content of these fibers.

SUBSTANCE WHICH IS ADDED TO AN INK TO CHANGE. the material on which the printing is to be done.

TENSIOMETER (OR TENSIONMETER). 1) an instrument used to measure the tautness of screen mesh in Newtons per centimeter; (2) an instrument to measure surface and interfacial tension of liquids, or tensile strength of solids.

THERMOCOUPLE. Used to measure the temperatures in the screen printing process using a thermocouple probe such as Atkins probe.

THIXOTROPHY. The property exhibited by certain fluid compounds to reduce their viscosity, when shaken and to recover it when subsequently put at rest, without having changed the temperature.

THREAD COUNTER. Magnifying glass or lens used to determine the number of threads (strands) per cm (or inch) of a screen mesh.

TRANSFER. Process of printing a mirror image of a design on transfer paper. The ink is partially cured, then transferred to the substrate by applying pressure and heat. Also called “textiles decalomania” or “printing by heat transfer”. Procedure which is widely used in textile printing.

VEIL. Thin transparent coat of emulsion that blocks the passage of ink in a screen mesh. Can be due to multiple causes, mainly under-exposure.

VISCOSITY. Thickness or fluidity of inks. It is any property that determines the amount of resistance opposed to the shear forces. High viscosity means it is thick and low viscosity means is is less dense (liquid).