In the printing process, lead to spot color ink production chromatic factors are many, these factors are discussed.

The influence of paper on color  

The influence of paper on ink layer color is mainly reflected in three aspects.  

(1) paper whiteness: paper with different whiteness (or with a certain color) has different effects on the color of the printing ink layer.  For the same kind of white paper, the whiteness is different, the color difference of the printing ink layer is mainly reflected in the black ink composition of the special color ink, especially for the color of lightness in more than 70, the influence is particularly obvious, resulting in the ratio of the special color ink is very different.  Therefore, in the actual production should try to choose the same whiteness of paper printing, in order to reduce the impact of paper whiteness on printing color.  

(2) absorbability: the same ink in the same conditions printing to different absorbability of paper, there will be different printing gloss.  The structure of the paper determines the surface of the paper there are concave and convex and pores formed by the plant fiber, in order to make the paper surface to obtain good uniformity and smoothness, generally in the paper surface coated with different thickness of paint.  The properties and thickness of the coating determine the absorbability of the paper surface to ink.  Absorption capacity is different, it is necessary to make the color of the printing ink layer difference.  Non-coating paper and coating paper compared, black ink layer will appear dark, matte, and color ink layer will produce drift, by cyan ink and magenta ink to match the color of the most obvious performance.  

(3) gloss and smoothness: printing gloss depends on the gloss and smoothness of the paper.  The surface of printing paper is a semi - gloss surface, especially coating paper.  

On a color print, when light hits the surface of the paper at an Angle of 45°, about 4% of the light is reflected off. This is the light reflected from the first surface.  And the rest of the incident light through the ink layer, through the selective absorption of ink, and then reflected through the ink layer, into the human eye, perceived by the human eye, this is the color we observe.  If the gloss and smoothness of the paper is high, the first layer of surface reflected light is a mirror reflection, not easy to enter the human eye, the color is basically observed through the ink layer reflected color.  If the surface of the paper is rough and low gloss, the light reflected from the surface of the first layer will be diffused, and the color we see at this time is the mixture of the main color light and the light reflected from the surface of the first layer.  Because this contains white light components, so reduce the saturation of the main color light, so people feel the color becomes lighter when observing printing, with density meter measurement density value is reduced, brightness rise.  

The effect of surface treatment on color  

The surface treatment of packaging products mainly includes laminating (light film, matt film), glazing (cover light oil, matt oil, UV varnish), etc.  Printing after these surface treatments, there will be varying degrees of hue change and color density change.  These changes are divided into physical changes and chemical changes.  The physical change is mainly reflected in the increase of specular and diffuse reflection on the surface of the product, which has a certain influence on the color density.  When covered with bright light film, bright light oil and UV oil, the color density increased;  When covering matte film and matte oil, the color density decreases.  Chemical changes mainly come from coating glue, UV bottom oil, UV oil contains a variety of organic solvents, they will make the color of the printing ink layer change.  

Influence of diluent on color 

Diluent is a paste of colorless transparent material in spot color printing mainly plays a role in diluting colors.  The influence of different amount of diluent on hue is also different, especially blue.  

In the process of preparing special color ink, the shear force and pressure of ink produced by ink leveling and ink spreading apparatus are smaller than those on the printing press.  In printing, it is not necessary to add the diluent, but only when adding the diluent in the production of color card with ink, can the uniform color of the ink display card be produced.  In the case of the same color density, color card and printed matter color is the existence of chromatic aberration, this is because the addition of diluent, change the distribution of pigment in the ink, so that the ink absorption, refraction and reflection of light have changed, resulting in chromatic aberration, this chromatic aberration is caused by the difference in the system.  

Effect of dry - fading density difference  

Just printed printing, ink is still in a wet state, and dry state when a density difference.  The phenomenon that the density of wet color is greater than that of dry color is called the phenomenon of dry fading density.  This is because the ink layer just printed has a certain level, so the surface reflection is mainly mirror reflection, looks bright and shiny.  When the ink layer is in a dry state, the surface reflection is mainly diffuse reflection, and the color and lustre is naturally darker than when it is just printed.  

Because dry color density can be measured after 30 ~ 60 minutes of drying, it brings difficulties to the measurement and control of spot color density.  

The density meter with polarization mirror device can eliminate the ink layer surface due to mirror reflection and light, the measured wet color density and dry color density is very close, so that the measured density value is not affected by the ink layer dry and wet.  For coated paper, the density difference is 0.05 ~ 0.15, and for non-coated paper, 0.1 ~ 0.2.  Different colors vary, with yellow having the least difference, black the most, and blue and red in between.  Therefore, when such a densitometer is used to measure, the measured value should be appropriately higher than the density value of the standard color sample, so as to play the role of control.