To test dry properties of flexo inks a standard print on a substrate is necessary. Such a print must be made under standard printing conditions with a printing device following the flexo principle. In flexo three types of ink are used: water based, solvent based and UV-drying inks The water based and solvent based inks have a very low viscosity and dry very quickly. For these inks it is impossible to use an offset system like Global Standard Tester with inking unit. The UV-drying inks have a viscosity like a paste and dry only by exposure to UV-light. In principle this type of ink can be used with a system of Global Standard Tester with inking unit but there can be reasons (printing quality) to use a flexo system.
To print the flexo inks there is an accessory which can be used with the Global Standard Tester 2. The system can be used for all types of flexo inks. The principle of the system is a flexo printing system comparable to practice. The prints, made with this system can be used to test the dry properties like colour, adhesion, light fastness, chemical resistance, and so on.
Principle
The flexo system for the Global Standard Tester 2 consists of an anilox roller with a doctoring system, a photopolymer printing form and an impression cylinder. The ink is applied to the anilox roller and the surplus is wiped off with the doctoring system. The ink is transferred from the anilox roller to the printing form and from the printing form to the substrate. The anilox roller is placed on the top shaft of the Global Standard Tester 2 and the impression cylinder on the bottom shaft. The photopolymer is mounted on the sector. The substrate is stuck on the impression cylinder with a piece of tape. The anilox force, the printing force and the speed can be adjusted. Also the number of inkings of the printing form can be adjusted.
There is a wide range of anilox rollers (ceramic and copper engraved). All these parameters make the system very flexible. All flexible substrates like paper, plastic films, foils and so on, can be printed.
Method of operation
• It is recommended to execute the test in the standard atmosphere; to most standards it is 23.0 ± 1.0 °C (73.4 ± 1.8 °F) and 50 ± 2% rh.
• For the operation of the Global Standard Tester follow the instructions of the manuals, IGT information leaflet W100 and the displays accurately.
• Handle the samples carefully.
Assessment
1. For colour measurement: check the colour visually in comparison with the original sample or measure the colour with a spectrophotometer.
2. For dry properties in general: check the desired dry property according to the testing method valid for that property
3. Repeat points 1 or 2 for each test strip.
4. Calculate the average and if required the standard deviation. In some cases it may be useful to mention the highest and lowest value as well.
