A colorimeter is a specialized instrument used to quantify and control the color of plastic products, ensuring consistency across production batches and compliance with design standards.
The emergence of color measuring instruments provides an effective tool for color measurement and control in the plastics industry. With increasing demands on plastics, the appearance quality of plastics directly affects the market competitiveness of products. Therefore, measuring and controlling plastic color has become an essential part of the work.
Principles of Plastic Color Measurement
Color measurement is a very important step in the production process of plastics. By measuring the color of plastics, we can obtain color standards and thus ensure the quality of plastic products.
Traditional color measurement methods typically use tristimulus values to represent plastic color. Tristimulus values refer to the intensity of visible light at specific wavelengths. By measuring these values, the RGB components of a color can be determined. RGB components represent the three primary components of a color image: red, green, and blue.
However, the traditional tristimulus method has several problems. First, the tristimulus value method cannot represent all possible colors. Second, the tristimulus value method has different sensitivities to different light sources, which results in different RGB components under different light sources.
Currently, several new methods have emerged to derive RGB components. These include representing color using four-stimulus values, five-stimulus values, hexadecimal, or Lab color space. Lab color space is a balanced color space capable of representing all possible colors. Four-stimulus values, five-stimulus values, and hexadecimal are all derived from intensity measurements at different wavelengths. Lab color space also derives RGB components from intensity measurements at different wavelengths, but it also includes two parameters: luminance and chroma. Luminance is composed of brightness and saturation, while chroma is composed of luminance and hue.
Plastic Color Measurement Methods
This section introduces methods for measuring plastic color. First, we’ll explain the principles of plastic color measurement. Then, we’ll introduce three methods for measuring plastic color: a double-beam spectrophotometer, a spectrophotometer, and a colorimeter. Finally, we’ll compare these three methods and select the optimal one.
Plastic color control methods
There are generally two methods for plastic color control:
1. Colorant control method: Adding an appropriate amount of colorant can adjust the color of the plastic, but this method will have a certain impact on the performance of the plastic.
2. Adding substances to control the color of plastics. The color of plastics can be controlled by adding substances, but this method will increase the cost of plastics.
Plastic Color Measurement Instruments
Plastic color measuring instrument is an instrument specially used to measure the color of plastics. It can accurately measure the color of plastics, thus helping factories to classify, match and control plastics.
Plastic color control technology
By controlling the color of plastics, the appearance of plastics can be optimized.
Plastic color control technology optimizes the appearance of plastics by controlling their color. Color control is crucial in plastics production. On the one hand, it allows for the creation of specific colors based on demand; on the other hand, color optimization can reduce product variations caused by different raw materials. However, implementation also presents challenges. For example, factors such as the ratio of different raw materials, process parameters, and the production process can all affect a product’s appearance.
Core Functions of Colorimeters in Plastic Applications
Colorimeters perform two key roles in plastic color management, covering both measurement and control.
Precise Color Measurement
It captures objective color data by measuring the reflection or transmission of light on the plastic surface.
It converts color information into numerical values based on standard color spaces, such as CIE LAB, CIE LCH, or RGB, eliminating subjective visual judgment errors.
Color Consistency Control
It compares the color of the produced plastic parts with the pre-set standard color (target value) to calculate the color difference (ΔE).
It triggers alerts or adjusts production parameters (e.g., pigment ratio, processing temperature) in real time when the color difference exceeds the allowable range, preventing off-color products.
Key Considerations for Using Colorimeters with Plastics
The selection and use of colorimeters need to be tailored to the unique characteristics of plastic materials.
Plastic Surface Type Adaptation
For glossy or matte plastics, choose a colorimeter with adjustable measurement apertures and light sources to avoid errors caused by surface reflection.
For transparent or translucent plastics, select a model that supports transmission measurement mode, rather than just reflection mode.
Environmental Factor Correction
Ensure the measurement environment is free from strong external light interference, as ambient light can distort the color reading.
Control the temperature of the plastic sample. Changes in temperature may cause slight color shifts in some plastics, affecting measurement accuracy.
Compliance with Industry Standards
Confirm that the colorimeter supports industry-specific color standards, such as Pantone (for consumer goods) or RAL (for industrial plastics), to meet customer or market requirements.
What is the gloss unit and definition?
What is the unit and definition of gloss? According to international standards, the unit of gloss is specular reflectance (Specular Gloss), which is defined as the luminous flux (Lux) reflected by the specular surface per square meter.
1. Gloss unit and definition
Gloss units and their definitions
Gloss refers to the intensity of light reflected from a material’s surface, and is used to measure the material’s glossiness. Its unit of measurement is lumen per square meter, or LUX.
What is gloss? The degree of lightness or darkness of an object’s surface. According to international standards, gloss is 10 times the surface’s reflectivity. It is usually expressed in Imperial units (GU). Generally speaking, the higher the gloss, the better it feels.
2. Gloss measurement method
Gloss is a physical quantity that characterizes the intensity of radiation reflected from a material’s surface. It can be used to characterize a material’s quality and texture. This chapter introduces several gloss measurement methods.
3. Application of gloss
Gloss application
Glossiness is an indicator of an object’s surface condition, used to determine its brightness. Generally, higher glossiness indicates greater surface roughness. In real life, glossiness is often used to distinguish between different materials. For example, the glossiness of metals and plastics often differs.
4. Meaning of gloss meter values:
Gloss is the ability of an object’s surface to reflect light when it is illuminated by light. It is usually expressed by multiplying the reflectivity of the sample in the mirror (regular reflection) direction relative to the standard surface by 100, that is, G=100R/R.
In the formula, R is the reflectivity of the sample surface, and /R is the reflectivity of the reference plate. Perfectly polished black glass is used as the reference standard. Its sodium D-ray refractive index is 1.568. The specular gloss is calibrated to 105 gloss units for each geometric optical condition.
Therefore, different values indicate the glossiness of the surface. If the result is between 10-70 GU, the coating is considered semi-gloss and should be measured at this angle. If the result is less than 10 GU, the product is considered low-gloss and should be measured at 85°. If the result is higher than 70 GU, the product is considered high-gloss and should be measured at 20°.
5. Gloss meter measurement principle:
Gloss meter Gloss is a physical quantity that evaluates the ability of a material’s surface to reflect light under a set of geometrically specified conditions. It has a directionally selective reflective property. When we refer to gloss, we usually mean “specular gloss,” so a gloss meter is sometimes also called a “specular gloss meter.” Therefore, to measure the gloss of an object’s surface, components such as a light source, a reflected light receiver, and a data analyzer are required. Let’s take a look at the working principle of a gloss meter :
Light source G emits a beam of light through lens L1 to the measured surface P, which reflects the light to lens L2. Lens L2 converges the light beam to the photocell located at the light barrier B. The photocell performs photoelectric conversion and sends the electrical signal to the processing circuit for processing, and then the instrument displays the measurement result.
Under specified light source and receiver angle conditions, the ratio of the sample’s radiant light energy (luminous flux) in the specular reflection direction to the reflected light energy (luminous flux) of a standard black glass sample in the same specular reflection direction is the sample’s gloss value. For polished black glass with a refractive index of 1.567 at a geometric angle of 60 degrees, the specular gloss value is set to 100 (gloss units). The specific formula is as follows:
In many fields, gloss is more than skin deep. It’s a matter of trust, safety and reputation. The right shine on that car, and the buyer will be convinced of its quality. Inspectors can be assured of its performance when a protective coating has the correct gloss. Brand support Packaging with uniform gloss adds to brand recall.
The key to successfully utilizing gloss meters is not the equipment, it is the operator. Accuracy, carefulness, and accountability are the ingredients that transform common measurements into reliable results. In some ways, gloss meters don’t just measure reflection — they reflect the professionalism of the person holding them.
