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Manufacturers of transparent plastics know all too well that haze can present challenges in achieving the desired outcomes. Too much scattering of the transmitted light produces a cloudy appearance that impacts consumer quality perceptions of quality and buying decisions. As a result, upholding consistent quality requires sophisticated tools that accurately and scientifically quantify color and haze.

Spectrophotometers inspect these attributes objectively, providing numerical values to compare. These devices help eliminate product appearance variations so you can regularly and effectively meet consumer expectations for quality.

Choose the Right Color Spectrophotometer

Benchtop spectrophotometers are ideal for measuring color and ensuring uniformity in plastic products. To ensure consistency, manufacturers should measure points across the entire range of production.

Using a spectrophotometer to measure the color of transparent sheet plastic offers several benefits, such as:

• Accurate data: Spectrophotometers provide reliable color data that reflects its actual color.
• Repeatability: These instruments provide a repeatable way to measure color, minimizing errors and facilitating consistent color throughout production.
• Standard compliance: HunterLab's spectrophotometers follow industry standards for color measurement, ensuring consistency across the supply chain.

Spectrophotometers empower manufacturers across numerous industries to capture accurate color and spectral data. These measurements support regulatory compliance, conformance with industry standards, and quality assurance that keeps customer satisfaction and loyalty high. Modern solutions offer measurement through either transmission or reflectance optical configurations.

Learning more about these approaches, their ideal substrates and applications, and their differences will guide you to the best solution for your color measurement needs.

Understanding Color Measurement

Light is the foundation of color measurement, with its wavelengths in the visible spectrum ranging from violet at 380 nanometers to red at 780 nanometers. The energy a light source provides varies across the spectrum depending on the light source. When it encounters matter, its wavelengths are either reflected, absorbed, refracted, transmitted, scattered, or diffracted. The object's chemical makeup helps determine what photons it will absorb versus those it emits or transmits. These emitted or transmitted wavelengths then enter the human eye, stimulating its photoreceptors. Emitted or transmitted wavelengths are the colors our eyes ‘see’ depending on where the energy falls within the visible spectrum.

Color perceptions vary between humans, making visual comparisons unreliable and underscoring the need for scientific color measurement solutions. Spectrophotometers simplify the task by analyzing and quantifying color in widely accepted color spaces like CIELAB and CIE XYZ. Transmission and reflectance are the two primary configurations spectrophotometers use to capture and report color and spectral data.

Color Measurement Through Transmission

When spectrophotometers measure color by transmission, they pass light directly through the sample. An optical sensor on the opposite side of the sample collects the energy for analysis and reporting.

The Science Behind Transmission Measurement

Measuring wavelengths through the transmission of color quantifies them into a ratio called transmittance. In scientific terms, transmittance is the percentage of incoming light that passes through a sample. The sample will also absorb a certain amount of the energy, requiring precise calculations using the Beer-Lambert Law, which describes how light is absorbed when it passes through matter.

Transmission measurements typically need at least 30% of the source light to pass through the sample with the light source at a perpendicular angle.

Key Considerations for Choosing Transmissive vs. Reflective Measurement

Transmission measurements work for transparent to translucent materials that allow 30% or more of the light to pass through — even if the surface is textured, like etched glass.

Opaque samples, which don’t let enough light through, are better measured using reflectance.

Applications for Transmission Color Measurement

Common applications for transmission color measurement include quantifying color in:

• Foods and beverages: Products ranging from edible oils to fruit juices and food dyes are compatible with transmittance measurement.
• Plastics: This approach is widely used in the plastics industry for food and beverage containers, transparent sheets and film, eyeglass lenses, and medical equipment like syringes, IV bags, and other clear medical devices.
• Chemicals: Use this method to quantify color in motor oils, lubricants, and petrochemicals.
• Pharmaceuticals: Injectable solutions and liquid medicines to monitor purity and detect any unwanted color changes.

Transmittance is also the most reliable color measurement approach for everyday products like clear liquid detergents and ophthalmic lense

Transparent plastic preforms are essential for companies that manufacture goods like beverages, edible oils, and intermediate chemicals like alcohols and glycols to form the container for the end product. The color of these preforms is equally vital, helping determine the final product's appearance and its impact on consumers' acceptance, buying decisions, and perceptions of quality.

Beyond influencing your customers, color consistency keeps manufacturing costs under control, since alterations can lead to waste. All cement the importance of color measurement at every stage of production to uphold quality assurance (QA) throughout the supply chain, from raw materials to finished goods.

The Challenges With Color Consistency in Transparent Plastic Preforms

Multiple factors can impact the appearance of transparent plastic preforms, from raw material variations to processing conditions and physical characteristics. All present specific challenges to overcome to achieve consistency and the desired appearance.

Variability in Raw Materials

Variability in raw materials is a frequent challenge for every plastics manufacturer, as well as producers who rely on plastic preforms.

Global regulatory bodies and consumers are embracing sustainability, leading to higher demand for the inclusion of more recycled polyethylene terephthalate (rPET). With this rising expectation comes new challenges, since rPET often contains high amounts of optical brightening agents (OBAs) to overcome yellowing. Every delivery of raw materials typically differs in that composition, making color measurement crucial to managing rPET variations successfully. Quantifying color at this stage empowers scientific, objective, and data-driven decisions to uphold aesthetics, quality, and performance.

Other challenges include variations in the amount and type of additives and pigments that can influence the final color. Additionally, contaminants like dust or residual color from previous runs may lead to alterations in appearance or clarity.

Physical Preform Properties

Transparent plastic preforms naturally present measurement challenges due to their physical properties.

Preform shapes and specifications represent the first difficulty. Contoured surfaces and variations in thickness inherently impact cooling rates, which can lead to alterations in color consistency. Inaccurate sample presentation can further influence measurement accuracy.

Additionally, transparent plastic preforms are susceptible to haze that affects color perception. This cloudy appearance is often caused by microparticles embedded within the plastic, which causes light to scatter when it interacts with the sample.

How Spectrophotometry Addresses the Challenges

Spectrophotometry is the most accurate and objective way to quantify color in transparent plastic preforms. Top-rated spectrophotometers solve the issues of manual visual evaluations — observer fatigue, error-prone assessments, and variabilities in surroundings that can affect how we perceive appearance.

Specialized Design for Transparent, Contoured Surfaces

This equipment provides scientific, numerical color data through specialized optical geometries and controlled lighting by measuring transmittance — the intensity of light at specific wavelengths within the visible spectrum that passes through the sample. Operators can then compare the readouts against established scales and indices, such as the Yellowness Index, to ensure the preform falls within acceptable tolerances, promoting consistent and repeatable results.

Higher rPET Content Without Guesswork

Tight color control with spectrophotometry is also how brands increase rPET without sacrificing appearance. When you have objective color data within seconds, you can raise recycled content while protecting appearance. Capture color measurement during incoming to set OBA dosing from data, not estimates. Using the same approach for in-process assessment and final inspection also helps identify alterations faster to uphold your quality control (QC) and support color consistency, even across different sites and suppliers.

Spices provide culinary flavor and visual appeal, and their color significantly influences perceptions of taste, quality, and freshness. Appearance alterations can identify processes that require changes to uphold color quality. Accurate spice color measurement provides quantifiable data to confirm whether spices meet accepted industry tolerances, quality standards, and customer expectations.

The Value of Accurate Spice Color Analysis

Several compelling reasons to measure spice color are:

• Quality control: Consumers judge food quality by color, and high moisture content, temperature fluctuations during storage, and spice age significantly impact appearance. Quantifying and monitoring the color quality of spices supports higher-quality end products.
• Business impact: People also expect certain spice colors to enhance food's visual appeal. Consistently delivering the desired color fosters brand loyalty and can create lifelong brand enthusiasts.
• Conformance with standards: Some spices, such as paprika and oleoresin spices, have specific industry standards they may follow. Other spices use different industry-recognized color spaces, like Hunter L, a, b. Accurate measurements document conformance with frameworks.

Integrating Measurements Throughout Manufacturing

Taking multiple measurements allows manufacturers to monitor the color quality at critical production points, simplifying issue identification and empowering early resolution to reduce waste. Quantifying data at various stages also pinpoints where color alterations occur so you can proactively adjust. Consider implementing color measurement across production, from raw material inspections to in-process color data capture and finished product verification.

Sample Considerations for Spice Manufacturers

Spices come with unique color measurement challenges, including:

Sample Size vs. Cost

Sample size may not concern those working with low-cost spices like black pepper, but quantifying color in high-cost spices like saffron represents a more significant expense. Manufacturers of these more costly spices benefit from minimizing the sample amount required. A highly precise and accurate color measurement solution supports greater confidence in outcomes, even with smaller samples. The right tool also means less waste of valuable ingredients, so more goes toward retail shelves and your bottom line.

Nonuniform Materials

Spices are naturally nonuniform, containing various textures, sizes, and shapes from their processed plant parts. Blends like seasoning salt or curry powder further increase complexity with a mix of different spice ingredients. These variations make visual comparisons unreliable and accurate data capture challenging without the right technology.

When you invest in the best spectrophotometer for measuring wig color, you can ensure that your synthetic wigs look nearly identical to real hair. Image source: Pexels user iiii iiii

The synthetic wig business is booming. Every year, more customers buy synthetic wigs and hair extensions in order to test out new fashion trends or make their natural hair appear fuller and healthier. This nearly $230 million market has grown by an average of 4 percent in value every year since 2011, and this trend is expected to continue.1

However, when modern customers invest in today’s synthetic wigs, they expect a much higher level of quality than previous generations of wig wearers. Today’s customers want wigs that look identical to real hair, from the texture of the fibers to the layers of color in the dye. To create realistic, trendy, and fashion-forward synthetic wigs, you’ll need to invest in the best spectrophotometer for measuring multidimensional color. This will allow you to perfectly mimic the look of real hair without paying premium prices for actual human hair pieces.

Why Many Manufacturers Choose Synthetic Wigs

The reason many manufacturers and customers choose synthetic hair, rather than real human hair, is largely due to price and availability. Real human hair takes years to grow, and wig manufacturers have to compensate the people who choose to grow their hair for use in wigs (unless they donate their hair). This means that real human hair wigs are more time-consuming to make, cost more up-front and require a slightly more complex manufacturing process in order to produce products on a mass scale. Real wigs cost anywhere from $800 to $3,000, sometimes more.2

By contrast, synthetic wigs are far more affordable for manufacturers and customers alike. Synthetic fibers can be made on a mass scale almost instantly — there’s no need to wait for the hair to grow. Most synthetic wigs sell on the market for an average of $30 to $500, depending on the quality of the synthetic materials; even the most expensive synthetic wig costs less than the cheapest real human hair wig. However, while synthetic wigs are cheaper to make, they also look and feel less realistic than real hair, especially if you dye the hair improperly. One of the biggest mistakes that wig manufacturers make is dying their products one flat color or using fibers that are too shiny. This is where a spectrophotometer may help.

The most realistic-looking synthetic wigs are multidimensional in color, just like real hair. Image source: Pixabay user Alexas_Fotos

Liquid chlorine presents unique challenges to the color measurement process due to its caustic nature. Image Source: Shutterstock user StacieStauffSmith Photos

Caustic liquids play many critical roles in our lives, whether in the form of pharmaceuticals, automotive chemicals, or everyday cleaning products.1 For example, many swimming pools are disinfected with liquid chlorine, even though this substance is highly caustic and corrosive when handled on its own. How do manufacturers ensure that a highly acidic gas like chlorine is safe to use in a public pool? By testing it thoroughly during the manufacturing process. Liquid chlorine manufacturers add a strong base (like caustic soda) to their products to counteract the high acidity of natural chlorine gas.2 From here, they also thoroughly test the final liquid product for pH balance, color consistency, and purity, ensuring that each batch of liquid chlorine is the same exact shade of translucent yellow.

However, performing color quality control tests on chlorine and other caustic chemicals can be a challenge for liquid chemical manufacturers. That’s because these materials need to be handled and tested with extreme care; if a caustic substance comes into contact with your skin, it could cause a painful chemical burn. Substances like chlorine also have corrosive properties, meaning that the chemical has to be stored in a nonreactive container (like glass or anodized metal) when you perform color quality control tests on the sample.

Yet despite these challenges, there is a simple way to test the color of these caustic liquid chemicals without putting your equipment or your staff at risk. By refining your testing procedures and using a durable spectrophotometer that is designed to handle harsh chemical samples, you can safely test the color of your products.

A durable spectrophotometer can help you safely test the color of caustic or corrosive liquid samples. Image Source: Shutterstock user Live and Learn

Some natural dyes are rare and difficult to manufacture in mass quantities, making them more expensive to produce. Image Source: Shutterstock user Nik Merkulov

Centuries ago, Tyrian purple, a reddish-purple dye made from the fluid of murex shellfish, was the most expensive fabric and paint dye in the world at over $19,000 per pound in today’s currency. This high cost reflected the extreme difficulty of production; it required hunting the specific shellfish species that produced the dye and carefully extracting the tiny amount of purple liquid inside of every shell. It took thousands of shellfish to make a single pound of Tyrian purple and the color was so rare and expensive that it became a status symbol for royalty and the ultra-wealthy at the time.1 For hundreds of years, purple was seen as a royal color, a tradition that continues even today, all because of Tyrian purple’s almost prohibitively expensive manufacturing process.

Today, purple dye is much more common than it once was. Modern textile and paint manufacturers have relatively inexpensive synthetic sources for purple, such as Mauveine, made artificially from coal tar.2 However, although the invention of a wider range of synthetic dyes has made dyed products easier to manufacture than ever before, there are still a number of commercial dyes used today that remain rare or very difficult to make.

When manufacturers choose to use these uncommon, expensive dyes in their products, however, they face a major challenge: they need to test their dyes and products for color consistency, but they also want to avoid wasting product during the testing phase. In order to solve this problem, manufacturers can use spectrophotometers that are capable of testing very small sample sizes. By shrinking the size of their test samples, manufacturers of expensive or rare dyes can thoroughly test their products for color consistency while also keeping their overhead costs as low as possible and preserving scarce materials.

Many natural dyes can be difficult to find or expensive to manufacture. Image Source: Shutterstock user piyaphong