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Explaining Spot Color Ink Mixing Techniques

Posted on 04-29-2024 by

Currently, spot color ink mixing methods mainly include traditional spot color ink mixing and computer-based spot color ink mixing. Based on the research experience in spot color ink mixing for offset printing, some suggestions are proposed for spot color ink mixing techniques for reference by peers.

Traditional Spot Color Ink Mixing Methods

Traditional spot color ink mixing methods rely on the skills and experience of operators accumulated over many years, using observation and comparison to achieve color mixing. This method is generally suitable for small packaging printing companies with low color requirements. However, many companies have reported that even with reasonable application of this method, there are significant color differences between the printed materials and the originals, leading to a high rate of defective products, which severely impacts normal production.

It is understood that when comparing the spot color mixed using traditional methods with the original spot color, the usual practice is to manually mix the ink first and then compare it with the original spot color. However, this approach is not scientific because the uniformity and thickness of the ink layer greatly affect the color effect of the spot color ink. When the color of the mixed ink is not significantly different from the original color, operators may mistakenly believe that the spot color ink has been properly mixed and begin printing, resulting in significant color differences between the printed materials and the originals. Combining traditional spot color mixing methods with mechanical ink mixing mechanisms can reduce color deviations caused by judgment errors.

In addition, the influence of paper on the effect of traditional spot color ink mixing should not be overlooked. Different paper materials have different effects on the color presentation of printed materials. Therefore, during the process of pattern production and comparison with the originals, it is necessary to use paper of the same material as the printed materials.

Even with these improvements, the phenomenon of metamerism may still occur due to improper color selection. This phenomenon manifests as two color printing samples appearing the same under one light source but different under another light source. Therefore, it is recommended to use computer-based spot color ink mixing whenever possible.

Hengsong Computer Spot Color Ink Mixing Method

Large packaging printing companies with higher color requirements typically use computer-based spot color ink mixing methods for color matching. The principle involves first measuring the target color using a spectrophotometer, processing it with computer color matching software to objectively represent the color information of the target color, and then using basic color data stored in the database for color mixing. The computer calculates the spot color ink formula that closely matches the hue of the target color. When significant color deviations occur between the matched color and the target color due to factors such as raw material properties and process parameters, the computer color matching system automatically adjusts the formula used to keep the color deviation within an acceptable range.

To accurately reproduce spot colors, optimization of computer-based spot color ink mixing techniques is necessary, with attention to the following points:

1. Accurate sampling of primary colors is crucial, as it directly affects the color matching effect. Therefore, when establishing primary color standards, strict and meticulous procedures are necessary to eliminate interference from external factors as much as possible.

2. Ensure stable ink transfer. Multiple experiments have shown that directly using an ink fountain to produce ink printing samples may not meet the higher color requirements of large packaging printing companies due to ink thickness and uniformity issues, mainly caused by overly thick or viscous ink, reducing ink transferability and resulting in significant color deviations. Before making samples, the ink should be placed in an oven at around 100°C, cooled for half an hour, to greatly improve ink flowability for better ink transfer. Additionally, accurate and clean ink weighing is necessary to avoid ink transfer issues caused by phenomena like floating colors or ink bleeding.

3. Substrates should be selected from the substrate to be printed on. Some substrate properties are measured and stored in the computer, while others are used to make primary color samples.

4. General principles and precautions for sample production: Samples should be made by the same person using consistent techniques; the ink for making a set of primary color samples should be weighed out at once; the conditions for making primary color samples should closely simulate production process conditions, with additives, amounts, time, temperature, and post-processing conditions similar to production conditions.

5. Try to use as few types of ink as possible for color mixing, as fewer types of ink result in better mixing effects and color saturation.

6. Select the same manufacturer or series of inks as much as possible during the color mixing process to avoid uneven color mixing. In severe cases, ink may coagulate and become unusable.

7. Ensure that the rubber roller of the IGT proofing machine is intact and clean. This has a significant impact on the accuracy of samples. When measuring sample data, three test points from different positions on the same sample can be measured, and the average value can be taken.

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