1. TAPPI : TAPPI represents the Technical Association of Pulp and Paper which is internationally accepted institution whose testing procedures for evaluating the qualities of the paper is accepted as reliable and accurate . The TAPPI testing methods are similar to ISO testing methods. There are several properties of paper that determines the suitability of Paper for various uses in printing and most of them are measurable by some testing method. The TAPPI authorized test method provide accurate and reproducible results as the TAPPI standard describe the calibration of testing equipment, the size of representative samples for testing, the room condition under which they are tested etc. TAPPI is run by highly devoted professionals dedicated to research and development. The TAPPI test results are universally accepted as approved methods. Since all presses can not afford to have their own in house testing labs in view of huge cost required they get the result tested from the reputed laboratories that keeps all the testing equipments and apparatus in centralized place. Some of the important Paper tests include Elongation test, tear Resistance, Double fold, Porosity, Oil Absorbency, Tensile strength, PH of Paper, Roughness etc. They are all testable using TAPPI standards.To read more on the TAPPI test methods and Standards click the following two links :
2. Tabloid: The word Tabloid refers to the single sheet or page equivalent to half the size of standard News Paper or 11’’ x 17’’. Newsletters are frequently printed on tabloid size paper (and then folded to letter size). Some of the sensational weekly Newspapers and Posters are often printed in tabloid size paper. Such Tabloid size News Papers are called Tabloid journalism. While universally many countries have accepted the ISO standards for the Paper sizes, the Tabloid paper dimensions are still officially used in USA and Canada both of who have not officially accepted the ISO standard for the paper. The most commonly used sizes of Paper in these two countries are Letter, Legal, Ledger and Tabloid.
3. Thermographic Printing : Thermographic printing is stimuli of Embossing derived by Die stamping process and also slightly resemble to Intaglio prints. The Thermographic print adds elegance, vibrant and gives 3 dimensional effect to an image. Thermography is a simple process used in conjunction with any conventional wet-ink printed by Letterpress and therefore is a post print process to give raised effect of prints. The Thermographic images which are slightly raised are shinier than embossed prints. Thermographic printing uses a colorless resin powder which is sprayed on the wet printed ink and fused through heat that melts the powder to cause images in relief ( not high relief but relief in touch). The inks that are used in this process should not contain too much of dryers or hardeners so that the ink will remain wet during the application of powder. This is an important factor that needs to be taken care of . While the quality of Thermographic print is not comparable to Intaglio print by any standards, the Thermographic printing is a low cost method of printing to get embossed images, which will also be not sharper, and used for producing business cards, invitations, greeting and gift cards, personal stationery, luggage tags etc . Thermography is cost effective solution to print raised images than the one obtained through engraved die printing process. There are automatic machineries and equipments which can be added with the printing machine to do Thermographic printing at a faster phase and are used by printers where huge volume of Thermographic printing is carried out. The technique of producing Thermographic image involves the following:
4. Thermochromic inks : Do not confuse it with Thermographic resin powder used in Thermographic printing. Thermochromic ink is a special ink used for printing on garments, Children’s play kits etc. In addition specially formulated Thermochromic inks are used for printing some of the security documents since the Thermochromic ink's reaction to temperature changes cannot be replicated on a color copier or laser printer. Thermochromic inks are sensitive to temperature changes and will appear or disappear at different temperature ranges. Therefore the inks are temperature activated to change their color and are manufactured in various temperature sensitivities as per customer demand provided the ordered volume is high. Otherwise the Thermochromic inks comes even to react in less temperatures such as 15-20°C. When rubbed with a finger, or held between the thumbs that has slight body heat, or exposed to differing temperatures, or blow through mouth the ink changes from a colorless state or to another color and quickly reverts to its original color.
- Print the matter in letterpress
- Immediately apply the resin powder on the still partially wet ink. The powder sticks to the wet ink.
- Dust it to remove the excess powder from the paper surface other than the one stuck on image. Alternately if you have a vacuum system, then remove excess powder from unlinked areas of the substrate or paper by vacuum.
- Then place the powdered image print inside a heat chamber or hold it above an low heat apparatus.
- The resin will instantly fuse or melt to show a embossed image
- Remove and stack it.
Thermochromic inks are specially formulated inks and are available in different colors and also as colorless inks. The inks can be formulated to act in pre determined temperature.
5. Thermal printing : Thermal print refers to those copies obtained on thermal papers which produce images by heat process. There are two types of thermal printers available to produce the digital images. One is the thermal paper, which has shiny look with very smooth feel. They have special coating that reacts with the beamed light source to change its colour to black on exposed areas. When the thermal printer transmit the image it turns into some form of electrical impulse and sends it to the printer head. The sheet reacts to the heat of the printer head which transmit the heat in a specific pattern. This pattern of heat transfer is responsible for creating images in the form of text, symbols or pictures. Many varieties of Thermal papers are available in the market.
The other form of thermal printer uses a ribbon coated wax base ink that melts and form the image by the heat element incorporated print head to cause the images to appear. In both the cases the digitally transferred light beam in micro dots causes the image to appear through heat process.
Color printing is also possible in Thermal printing. Thermal printers print faster and are noiseless than the Dot matrix printers though its system is similar to dot matrix printer only. While the dot matrix printer cause the images to appear by several pins that pushes the ribbon ink on to the paper, in Thermal printing the captured images turns into electrical impulses which heats up the print head to heat those portions of the images on the ribbon to release the wax ink on to the substance to form the image. Few of the classic cases that use the Thermal Paper include the Paper on Fax machines, ATM outlet receipts, hand held billing machines, Queue Coupon issuing machines in banks etc. The thermal printers cause the images to appear using internet transmitted images too. The classic example is the check in coupons issued in the Airports by hand held printers by the Airport staff. This printer works really well for standard text or black and white documents, and they generally print as fast as other printers. Thermal printers are more popular for printing the receipts because they are faster than most normal printers.
alphabet T to be continued under T/2