Industrial Color Spectrophotometer: Everything You Need to Know

Consistency of colour is one of the important factors in industrial manufacturing. Even small colour differences between product batches can have an impact on product quality, customer satisfaction, brand identity etc. A visual inspection may be insufficient, due to lighting conditions and human perception that can affect the way people interpret colors. An Industrial Color Spectrophotometer can be used to provide manufacturers with an objective measurement of color by measuring reflected or transmitted light and expressing the measurements in numbers. These measurements are used in quality control for metal manufacturing, packaging, textiles, paints and coatings and plastics industries. This guide covers the basics of color measurement, the types of color measurement instruments, and how manufacturers can choose the right one for their production.

What Is a Color Spectrophotometer?

A color spectrophotometer is a type of optical instrument which measures the reflectance or transmittance of a material at various wavelengths. It reads these and attempts to determine the numbers that represent the colour value, which aids in comparing the sample to the approved colour standard. A widely used system is called CIELAB: L* (lightness) defines a color's varying brightness, a* (green-red) indicates the position of a color on the green to red plane and b* (blue-yellow) denotes the position of a color on the blue to yellow plane. Colour difference values, like Delta E (ΔE), can be used to measure just how different a sample is from its reference. This method can measure and collect data that can be recorded, shared and used for consistent quality decisions, unlike a visual inspection only method.

What Is the Purpose of a Color Spectrophotometer?

A color spectrophotometer's primary function is to assist the manufacturer with the color uniformity of a product during the manufacturing process. It can help in quality control of incoming raw materials, batch comparison, quality control of finished products, color difference detection, etc., before the occurrence of rejected products. Manufacturers can, for instance, use colour measurements to verify that the colour of plastic housings, coated metal parts, textiles or packaging materials is in accordance with an approved standard. The instrument can also be used for supplier quality control and for teams to communicate colour requirements in a numerical value, instead of a subjective description. Early detection of unwanted colour changes helps businesses minimize rework, material waste and colour differences between products.

How Does a Spectrophotometer Measure Color?

The spectrophotometer is a tool which measures colour, either by reflecting light on a sample or by passing light through it. Depending on the type of instrument, the optical system will disperse the light into the different wavelengths and a detector will provide a measure of the reflected or transmitted light. This is then translated to a spectral profile by the instrument and the color values are calculated based on selected settings. These settings can be the illuminant, standard observer, measurement geometry and colour space. The CIELAB system, for instance, can be used to describe colour direction and lightness, and ΔE can be used to describe how different two measurements are, using a selected formula. It is important to have calibration and the same measurement conditions since the results will change when there is a change in sample preparation or instrument conditions.

How Can a Spectrophotometer Be Used to Measure Color?

It is essential to have an instrument appropriate to the material to be measured and that the required color standard is correct. This is followed by calibration following manufacturer's directions and collection of a clean representative sample. Sample needs to be set up, proper measurement modes need to be used prior to taking readings. Users can then measure and compare the values of the colour of the sample to that of the reference. If the surface of the product is uneven or a variation in colour is evident, a number of representative points may be measured to give a better indication of the product. It is helpful to document the instrument settings and results so that it is easier to make comparisons in the future.

Using a Spectrophotometer for Color Measurement

It is essential to have an instrument appropriate to the material to be measured and that the required color standard is correct. Calibration of the instrument based on manufacturer's instructions and preparation of a clean and representative sample are the next steps. The sample should be in the proper position and the appropriate measurement parameters should be set before the measurements are made. The users can then measure the sample and compare the values of its color with the values of the reference color. If the surface of a product is not even, or a color change is observed, it may be more useful to make measurements at several representative locations. The instrument settings and results should be recorded to ensure future results are reliable.

Main Types of Color Measurement Instruments

There are various types of color measurement instruments which are used for different purposes. Some have been developed for rapid measurement on production floor; others are more sophisticated laboratory measurement or to evaluate appearance in a specific light source environment. The type has to be chosen based on the sample, the necessary level of detail and a quality control process.

Portable Color Spectrophotometer

Portable color spectrophotometer is a handheld spectrophotometer which can measure samples directly in production areas, warehouses or supplier's facilities. It offers the advantage of being compact enough to be useful in checking large parts which cannot be easily transported to a laboratory. It is a tool that can be used by manufacturers to test plastics, metal surfaces that are coated in paint, fabric and other coated products. In choosing a portable type, one should take into account the aperture of the measurement, the battery life, calibration, data storage, and the accuracy of the measurement of the material.

Benchtop Color Spectrophotometer

A benchtop color spectrophotometer is designed for use in the laboratory for testing and controlled measurement procedures. Can give repeatable results for samples placed and measured under specified conditions. These instruments can be used for testing of plastics, powders, paints, coatings and other materials which can be brought to a work station. They can include complex software, several measuring settings and in-depth color reports, depending on the models. They are particularly useful if a manufacturer requires some form of standardised method for comparing samples from the various batches of production.

Liquid Color Spectrophotometer

A liquid color spectrophotometer measures the color of transparent or translucent liquids, by using a suitable transmission or other validated measurement method. The sample is typically inserted in some form of cuvette or sample cell where light will pass through the sample under controlled conditions. Examples are chemicals, beverages, oils and other liquid products. A path length, cleanliness and suitability of the sample cell may influence the readings. Manufacturers should choose an instrument and method which will correspond to the properties of the liquid and the required colour scale.

Colorimeter / Color Lookup Device

A colourimeter measures colour by means of sensors or filters that are arranged to mimic the human colour sense. Often suitable for routine colour checks when a simpler method of measurement will satisfy the application. In addition, a colour look up device can assist users to match a measured colour to stored colour libraries or references. Unlike a spectrophotometer, a simple colorimeter will not give as much detailed spectral information. Depending on the task of colour check and colour matching, either of these tools may be chosen.

Light Booth

A light booth is used for the visual colour inspection in controlled light. It enables the user to view samples under the chosen light sources, and to compare the samples more consistently. This is helpful if it is necessary to determine if materials from various suppliers seem to be the same. Another way to detect metamerism (the appearance of similarity under one light source and difference under another) is by using a light booth. But it is not a substitute for an instrument which measures color numerically. An evaluation by a controlled visual inspection plus instrumental readings can be used to give a more thorough evaluation.

Appearance Instruments

Appearance Instruments measure the characteristics which affect the appearance of a product other than basic colour. This can include gloss, haze or other optical and surface properties of the device. These measurements are significant for finished parts, plastics, coated products and polished metal parts where the appearance of the surface is important to the quality of the product. For instance, two parts could have the same color reading, but the parts could look different due to the finished gloss and/or texture. Defining the appropriate appearance properties and measuring them can enable the investigation of these differences more effectively by the manufacturers.

Specialized Systems

Special colour measurement systems are developed for materials or applications with specific measurement procedures. They can be used, for instance, in powder systems, for textured surfaces, translucent plastics, fluorescent materials, and in many industrial systems with complex parts. There are specific sample holders that are required for some applications, larger measurement areas, specific software or customized testing procedures. Manufacturers should ensure that a specialist system is in place that allows for the material(s) to be processed, and that the results of the system can be correlated with the material requirements of their own product.

How to Choose the Right Color Spectrophotometer Instrument

To choose an appropriate instrument, it is important to understand the product, the production process and the requirements of the product's colour quality. Before making a decision, manufacturers should examine the measurement performance, sample compatibility, ease of use and long-term operating requirements of the two types of oligocectometers. The environment in which the products will be inspected should be used to determine the reliability of the results produced by a suitable Industrial Color Spectrophotometer. The following are some considerations that can be used to help inform the selection process.

Determine Your Industrial Application Requirements

The first thing to do is to find the materials and products that require color inspection. Different methods of measurement may be necessary for parts made of plastic, metal surfaces, paints and coatings, textiles, powders and liquids. Take sample size, surface, transparency, gloss, production quantity and acceptable colour difference into consideration. For instance, an aperture for measuring a small molded part can differ from the aperture used for measuring a large coated panel. It will be best to identify these requirements first so that the appropriate instruments can be used to narrow down the selection of the instruments that do not support the application to avoid paying for a feature which is not needed.

Determine the Configuration and Geometric Shape of the Color Spectrophotometer

Measurement geometry refers to the way that the instrument lights the sample and to the way that it captures reflected light from the sample. The two most frequent ones are 45°/0° and diffuse/8° (d/8°). A 45°/0° instrument measures light at defined illumination and viewing angles, while a diffuse/8° instrument provides diffuse illumination and will collect light at an 8° angle. There are some diffuse/8° instruments which may be set up to measure with specular reflection included or excluded, depending on the setting.

The correct geometry will vary according to the product specification and whether or not the surface gloss needs to affect the result. The aperture size and shape of the instruments also becomes important in the measurement of small parts, curved parts, and irregularly shaped parts. Make comparisons using the measurement configuration specified by the relevant quality standard or customer specification.

Consider Using Advanced Features to Enhance Usability

New color measurement devices can provide functionality that can make routine checks and reporting easy. With this aim in mind, features such as automatic calibration, built-in color standards, color difference calculations, wireless data transfer, data storage and integration of quality control software would be useful. A few models also provide the ability to measure multiple illuminants, standard observers, color spaces and measurement modes.

Select features, depending on your production process. For instance, batch tracking and report exporting may prove helpful if there are multiple operators operating the product throughout the day. There are also easy-to-use software that can be used to identify the colour trends and communicate these findings to both suppliers or customers. Prior to purchase verify the features are compatible with your current quality management procedures.

3nh Color Measurement Solution

3nh is a brand for Color Measurement instruments and Testing Equipment. The manufacturer should get a comparison of the portable versus the benchtop, measurement geometry, repeatability, software and sample type that can be measured. This will depend on which type of application they are using – plastic parts, coated metal parts, powder, liquids etc.

When considering a 3nh solution, check the official product specification and make sure that the instrument meets the need for the required measurement and tolerances. It may be helpful to test representative samples prior to purchase to determine if it will meet the desired quality control requirements.

Conclusion

A color spectrophotometer can assist the manufacturer to transform the differences in color into measurable data. Helps with Quality Control, colour matching, production consistency and supplier/customer communication. To select the appropriate instrument, one must consider such factors as sample material, measurement geometry, instrument performance and features. A good QC system coupled with appropriate calibration, with consistent measurement practice and with clear acceptance limits can be immensely valuable when using an Industrial Color Spectrophotometer. Manufacturers will be able to make sure equipment meets their colour needs and products will have uniform colour when selecting the equipment according to application requirements.