The Craft of Offset Ink Mixing

Posted on 04-16-2024 by

The mixing of ink is a crucial task in offset printing, as its quality directly impacts the printed product. Since vibrant colors, good brightness, and accurate hues are fundamental requirements for offset printing products, achieving this necessitates accurate ink mixing. Therefore, operators must grasp basic color knowledge and ink mixing techniques.
 
1. Understanding the Law of Primary Colors Variations for Accurate Ink Mixing
 
We know that any color can be mixed by varying the proportions of the three primary colors. The variation in ink hues is precisely based on this law. For instance, mixing equal amounts of primary color inks can result in black (approximately). By mixing primary color inks in equal proportions and adding different proportions of white ink, various shades of light gray ink can be obtained.
 
Mixing primary color inks in various proportions can produce many intermediate or compound colors, but their hues tend to lean toward the hue of the primary color with the larger proportion. Additionally, adding white ink to any color ink makes its hue appear brighter, while adding black ink makes its hue darker. The mixing of various colors of ink, based on the subtractive color theory, is used to create different colors.

2. Analyzing the Hue of the Original Manuscript and Using the Complementary Color Theory to Correct Color Bias, Improving Ink Mixing Results
 
Upon receiving a printing color draft, careful appreciation and analysis of the colors in the original manuscript should be conducted, evaluating the proportions of ink hues required for mixing.
 
Analyzing the color draft involves mastering a basic principle: the three primary colors are the basis for mixing any ink color. Generally, using the law of variation of the three primary colors, any complex color can be mixed, except for metallic colors. However, in practical applications, relying solely on primary color inks to mix countless ink colors is not enough.
 
This is because the pigments used in ink manufacturing are not always standardized, and even each batch of ink produced inevitably contains some degree of color difference. Therefore, in actual work, additional ink colors like cyan, dark blue, light blue, fluorescent blue, medium yellow, dark yellow, light yellow, gold, orange-red, dark red, light red, black, and green should be added in appropriate quantities to achieve the desired ink hue. While there are many types of ink, apart from primary color inks, all other colors are used to supplement the deficiencies of primary colors.
 
Any complex color always changes within the range of the three primary colors. By mastering this principle, ink mixing becomes straightforward. Once the color analysis determines the main and auxiliary ink colors and their proportions, mixing can proceed. However, if the resulting hue has deviations, the complementary color theory can be used to correct it. For example, if a green hue is too pronounced, a small amount of red ink can be added to correct it. Conversely, if the red hue is too pronounced, blue ink can be added to correct it.
 
3. Mixing Intermediate and Compound Colors
 
Intermediate colors are those mixed from two primary color inks. For example, adding yellow to red yields an orange hue; adding blue to yellow produces green; adding blue to red results in purple. By varying the proportions, many intermediate colors can be mixed. For instance, mixing peach red and yellow in equal proportions yields a deep red hue; mixing them in a 1:3 ratio yields a dark yellow hue; mixing them in a 3:1 ratio yields a gold-red hue.
 
If yellow and blue primary color inks are mixed in equal amounts, a shade of black can be obtained; mixing them in a 3:1 ratio yields an emerald green hue; mixing them in a 4:1 ratio yields an apple green; mixing them in a 1:3 ratio yields a dark green. Mixing peach red and blue in a 1:3 ratio produces a deep blue-purple hue; mixing them in a 3:1 ratio yields an approximation of teal.
 
Compound colors are derived from mixing three primary color inks. By mixing them in different proportions, many types of compound colors can be obtained. For example, mixing peach red, yellow, and blue in equal proportions results in an approximation of black; mixing peach red in a 2:1 ratio with yellow and blue in equal proportions yields a reddish-brown hue; mixing peach red in a 4:1 ratio with yellow and blue in equal proportions yields a reddish-brown color; mixing peach red and yellow in equal proportions, and blue in a 2:1 ratio, results in an olive hue; mixing peach red and yellow in equal proportions, and blue in a 4:1 ratio, results in a dark green, and so on.
 
4. Operational Methods for Mixing Ink Colors
 
When mixing ink, based on the analyzed hue of the original manuscript, determine which ink colors are appropriate for mixing. For example, to mix lake blue ink, it can be achieved based on visual estimation and practical experience. White ink is the primary color, and peacock blue is the secondary color that should be slightly added. If a deeper hue is desired, a little brandy blue can be added.
 
Once the main ink colors are determined, other colors are auxiliary and should be gradually added in small amounts and stirred evenly. Then, using two pieces of paper (the same as the printing paper), apply a small amount of the mixed ink to one paper, and use the other paper to scrape it to the thickness of the ink layer for comparison with the original manuscript to see if it is suitable.
 
When comparing the sample manuscript, accurate observation of the thinner and lighter parts of the ink sample on the paper surface is necessary for more precise evaluation. When mixing ink, it is also essential to adhere to a principle: try to use as few different colors of ink as possible. In other words, if a hue can be achieved by mixing two inks, do not use three inks to avoid diminishing the glossiness of the ink.
 
Furthermore, the ink colors in the samples should be slightly darker than the original colors. This way, the colors printed from the samples will be more accurate. After adjusting the colors of the samples, batch ink mixing can be conducted based on the proportions of ink used in the samples to ensure the quality of ink mixing and improve work efficiency.
 
In summary, as long as we grasp the law of variation of the three primary colors, apply color knowledge, practice diligently, and analyze and summarize, we can accurately and quickly mix colorful inks with precise hues, vibrant colors, brightness, and good printability, laying a solid foundation for improving product quality.