SPECIAL TYPES OF PRINTING INK

 

SPECIAL TYPES OF INK 

1.                QUICK-SET INK: - Because coated papers and boards have a much more compact and less penetrate surface than uncoated stocks. The thick oils and varnish necessary in lithographic and letterpress inks are only slowly absorbed leading to the problems of set off in sheet fed and the possibility of blocking in reel fed operations. Low viscosity oils and solvents will be absorbed relatively very quickly. Quick set inks exhibit the principles of absorption drying by ink in cooperative a two part, oil system comparatively thin oil that is readily absorbed through the surface coating living the thicken oil, resin and pigment on the surface. The print then sets to a tough drying coatingwhich oxidation polymerizes more slowly to give a fully hardened film.

 

2.                MOISTURE-SET INK: - These type of ink are now commonly used by letterpress printer. These inks have the great advantages that they are free from unpleasant odour, which arises from the formation of certain per-oxides in the oxidation stage of the drying of a vegetable oil. The vehicle for this type of ink is one of the substances called di-glycols, which are carbon chain with hydroxyl group of each end.

3.                Heat- set inks- These are used in web offset are subjected to high speed hot air blower, this treatment evaporates solvents and minerals oils. The hot web is cooled by passing over chilled rollers to reduce the likely hood of acceleration of oxidation polymerization takes place because the rate of the chemical reaction increases with the temperature. The rate of drying doubles with every 100 rise in temperature.

4 Cold- set inks- The term cold- set is used to describe a printing method in which the ink is applied by lithography process to a absorbent substrate and dries by penetration. External heating is not applies, newspaper stocks is the principle material in this process. The penetration of ink into paper occurs in two stages. A rapid penetration under pressure at the movement of impression followed by a slower penetration forces.

5. Metallic inks- These inks are made from aluminium or bronze powders mixed with suitable resin solution the particles size of metallic powder used in inks are large than pigments particles to give metallic luster. The bronze powder and vehicle for repairing gold inks are mixed just before using, since the majoring of gold inks tarnish rapidly after mixing. Coated paper gives the best result to dry and over printed with gold inks. Both silver and gold inks can be printed Letter- press. Offset or gravure when printed by offset, alkaline or neutral fountain solution is used to prevent the tarnishing of bronze powder. 

Gold inks: -

Bronze powder = 30%

P.V.A varnish = 55%

Wax compound = 5%

Ethanol = 10%

Silver inks: -

Aluminum powder = 30% 

P.V.A varnish = 60%

Wax compound = 4%

Propylene alcohol = 15%

Aliphatic hydrocarbon = 5%

6.               Magnetic inks: - These inks are made with pigments which can be magnetized printing and the printing character is reorganized by electron reading equipments. The processing of checks and other security documents has made possible a highly Centralized cleaning system cleaning system. The inks are formulated using a synthetic iron- oxide pigments (Ferrous or Ferrous oxide), which has been dispersed in a medium with good wetting properties, such as low viscosity alkyd resin which may has been combined with a resin or oil varnish. The ink must have sufficient flow to distribute on the press, but also must have sufficient body to print the characters clearly, so that the correct responses are registered by sorting equipments. 

7.               Fugitive- security ink: - These inks require water soluble dye as the main coloring matter. The printed security has to be chemicals to overcome any attempt to forgery and hence water soluble dye stuff are used in coloring matter in such security ink. 

8.               Fluorescent inks: - These were formerly limited to screen- printing new finer grind pigments and greater pigments strength now permit color to be printed in one impression by letter- press, lithography and gravure. Duo tone and even full color process are now possible, The naturally bright inks reflects and emit light making uses of u.v (ultra violet ) ins, which other inks cannot utilize, the semi- transparency of inks permit over printing to achieve color mixture the pigment are not light fast fluorescent inks must be printer on a while surface. They appear most brilliant powder have the property of converting short wave visible radiation into longer permanent nature such a labels packaging products, hand bills, posters, etc. 

9.               High gloss inks: - Basically contains an extra quality of varnish giving them a glossy appearance when dry. For best results coated stocks should be used generally the more resistant the paper is to penetration of the vehicle. The higher the gloss this property of the paper is called hold out, gloss inks are made of synthetic resins and drying oils which doesn’t penetrate into the substrate as the other inks do. The resistance to penetration is what produces the high gloss. A combination of gloss ink with a paper that resists penetration will produce the best ink finish since the ink doesn’t penetration.