At Priority Printing we make metal plates, usually aluminum. Metal plates can last for over 100,000 impressions, hold finer detail, and allow tighter register than polyester plates, which were used in the past. CTP (computer-to-plate) imagesetters image metal plates using lasers. Metal plates can be preserved for future printing, as they generally do not wear out after just one printing.
Polyester Plates (CTP and Analog)
Offset presses have three printing cylinders (plate, blanket and impression) as well as inking and dampening systems. As the plate cylinder rotates, the plate comes in contact with the dampening rollers first, and then the inking rollers. The dampeners wet the plate so the non-printing areas repel ink. The inked image is then transferred to the rubber blanket, and paper is printed as it passes between the blanket and impression cylinders.Makeready is minimal. The wraparound plates can be moved slightly for proper register. The resilient rubber blanket compensates for the variable thickness and texture of paper stocks, largely eliminating a source of considerable trouble in other printing processes. A wide range of papers can be used. Halftones can be printed with text and solids on both rough and smooth surface papers.
Offset Sheetfed Presses
Sheetfed presses can print at speeds up to 15,000 impressions per hour and are made as single or multicolour presses up to 10 units. Sheetfed printing has the advantages that (1) a large number of sheet or format sizes can be printed on the same press, and (2) waste sheets can be used during makeready, so good paper is not spoiled while getting position, colour or ink-water balance up for running.
Sheetfed presses are available with perfecting features. The perfecting unit allows the press to print both sides of the paper in one pass through the press. Newer multi-unit sheetfed presses with coating towers are available with extended deliveries to provide space for infra-red drying or UV ink- curing units. Five of Priority Printing’s presses have perfecting features.
Lithographic inks are formulated to print using the principle that oil and water don't mix, and are generally very strong in colour value to compensate for the lesser amount applied. The average amount of ink transferred to the paper is about half that of letterpress because of the double split of the ink film between the plate and blanket and the blanket and paper.
The recent development of new vegetable oil vehicles has improved performance especially of new inks. It is a renewable resource which helps make the industry independent of petrochemical oil vehicles. Linseed and rapeseed oils have been used for years. The newest vegetable oil is soybean oil commonly referred to as soy ink, which has good printing qualities and eliminates smudging from newsprint. Priority Printing uses vegetable based inks.
These use metallic powders, such as aluminum and copper alloys, mixed with the proper varnish base, to give a pleasing metallic luster. This is because the powders are actually flakes which deposit in reflective layers. The bronze powder and vehicle for preparing gold inks are mixed just before using, since the majority of gold inks tarnish rapidly after mixing. The varnish used dries rapidly and has sufficient binding qualities to hold the powder to the paper surface. Coated papers give the best results. Metallic inks are generally more expensive.
These inks were developed to increase the speed and efficiency of handling bank checks. These inks are made with pigments which can be magnetized after printing, and the printed characters are later "recognized" by electronic reading equipment. These inks must be formulated to produce high-grade printing which will meet the rigid requirements of the reading equipment. Makeready and amount of ink must be precise and consistent.
Each of the 10 numbers and 4 symbols shown above has a distinctive shape which can feed information to a computer, which processes the information for a number of uses.
These were formerly limited to screen printing. New finer grind pigments and greater pigment strength now permit colours to be printed in one impression. Duotones and even full-colour process are now feasible. The naturally bright inks reflect and emit light, making use of ultraviolet light waves which other inks cannot utilize. The semi-transparency of the inks permits overprinting to achieve colour mixture. The pigments are not light- fast.
Fluorescent inks should be printed on a white surface. They provide maximum brilliance when contrasted with dark surrounding hues. Fluorescent pink is used as a fifth colour in 4-colour process printing to enhance skin tones, and extend the range of magenta hues in the images. Fluorescent ink is generally more expensive.
Varnish and Lacquer
Used as coatings over printing to protect the printing and increase gloss. Varnish is recommended on coated stock that has large solid areas that receive wear and tear such as book covers. Highly recommended on matte coated stocks.
Lacquers are applied on special coating machines. Most varnishes are applied on-press, from a blank or imaged plate inline with the printing on the press, and drying is by oxidation without heat. Gloss and other special characteristics are limited as the varnishes must be compatible with wet inks. Varnish can be tinted with regular inks for unique special effects.back to passport to printing bindery