Ink technical specification: 1. Color of ink Color is a direct-viewing important specification of the ink consumers; color also gives the ink consumers a first sensible impression. Because of the different hobbies and customs of the ink consumers, it is very hard to tell the right coloration, chromaticity and the depth. Generally speaking bright color with moderate depth is acceptable. Different inks require different specifications of the color. 2. Intermittence writing Intermittence writing is the cap-off time of the ink. Ink must not dry out fast on the pen tip, but must dry out fast on the paper. The longer the cap-off time is, the better the quality is. The cap-off time can be tested under certain temperature, humidity and wind power. We consider the intermittence writing as an important specification of the ink. 3. Divergency of ink Divergency is a specification to test the ink infiltration on the paper, ink with a good quality has no infiltration on the paper. 4. Stability of ink Stability is storing ink for a long time with no precipitation and metamorphic. It is very important for all kinds of inks. Inks are fine chemicals reacted and mixed by lots of chemicals, its stability depends on raw material reacting in acid and alkali medium. The good stability can be tested by storing ink for a long time under certain temperature with no precipitation and metamorphic. 5. Fastness of ink Ink fastness is the performance of the ink dry on the paper for waterproof and lightproof. Pigment inks have better performance for waterproof and lightproof. 6. Viscosity of ink Viscosity is a very important specification for pigment ink, especially for gel ink. Viscosity is a key specification for smooth writing, viscosity must match with different models of pens, pen tips. Different inks require different viscosity. 7. Particle size of ink Particle size is a specification for pigment ink. Particle size can be examed by microscope. When the particle size of pigment pellet is small and even enough, we consider the stability of ink is good. 8. Surface tension of ink Surface tension of ink is different from divergency. We can take effect on divergency of ink by control the surface tension, and also can take effect on infiltration of ink. Surface tension is an important specification for highlighter ink, water-based ink and gel ink, it can be examed by surface tension meter.