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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.

Color and appearance measurements for the beverage industry are used to ensure that the overall product appearance is the same from lot to lot. In the marketplace, it is rare that consumers are permitted to taste food products prior to purchasing them. However, they frequently can look at the product. They make a judgment decision largely based on overall appearance including color.

Coloring the mind of your Consumer:

Never has the consumer been more empowered than now in this digital age where knowledge of the products they purchase has been made available to them at a click or swipe, and this testifies that a greater need has evolved for the F&B industry to build a product with enticing visual properties such as Color and haze without compromising the highest level of quality. A strikingly similar parallel of ‘Go-Green’ campaign has also weaved it’s way in the Food & Beverage industry influencing the consumers to choose naturally colored products over artificially bright and unnatural Colored products, and this has birthed the need to test the quality of the beverage for Color consistency across all stages of the process like production and storage as the ingredient changes can alter the base color of a beverage, resulting in the perception that the product is different or of lower quality.

Diverse Optical Characteristics and their Methods for measurements:

The complexity of successfully measuring Color and appearance in the Beverage Industry is further enhanced by the fact that beverages are of types opaque, translucent or transparent, and each form requires different instrumentation and techniques. Opaque liquids have high solids content with a characteristic of high Brix value when light passes through it and Translucent liquids possess medium levels of solids and exhibits a lower brix value when light passes through it. Therefore, it is crucial for the food processors to assess the right measurement modes like reflective or transmittance before they measure the Color during any stage of processing. This significantly increases the need of a spectrophotometer to measure the spectral data values and also measure the transmission haze.

Chemical analysis is an intricate part of our everyday lives. From the water we drink to the food we eat to the fuel we put into our car, nearly everything we consume has undergone some form of chemical analysis before use. Although it’s likely not something we consider as we go about our daily activities, it’s a vital aspect of the production process for many things and something we all rely upon for quality assurance.

Petrochemical manufacturers know that chemical analysis is one of the most important steps in the monitoring of chemical compounds in the petroleum refining process. It is also one of the most unique and difficult processes to quantify and analyze. The ability to detect color changes is an important step in the process for identifying contaminants and impurities. With the right technology, the challenges of chemical analysis can be met.

Clear liquids are classified based on visual comparison.

Applications of Color Measurement in Petrochemicals

Petrochemical production results in a number of goods and materials that are dependent on accurate chemical analysis. From crude oil to the most refined petrochemical products, the manufacturing process relies on color technology to help with interpreting data, differentiation, and classifying petrochemical compounds. Petrochemical materials cover a wide range of products such as solvents, adhesives, plastics, resins, fibers, elastomers, lubricants, and gels. Each compound can vary from transparent to translucent to opaque, and accurate measurement is contingent upon the highest quality of instrumentation to measure transmittance or reflective materials.

The products that result from petrochemicals are numerous and varied. Image Source: Flickr user snowlepard

The petrochemical industry has greatly benefited from the use of color technology and spectrophotometers, and the ability to detect color changes throughout the refining process is an important step in identifying possible contamination. The ability to recognize even the slightest changes throughout processing helps to alleviate any impurities that may affect the quality of the final product. Detecting changes is crucial in monitoring and identifying any needs for re-distillation throughout the refining process.

Clear liquid purity is measured using the APHA color scale and is essential for ensuring product safety and consistency and many various industries. Image Source: Flickr user Nathan Forget

Purity is an important factor imperative in the foods we eat, the medicines we take, and the water we drink. However, visual analysis of clear liquid color measurement is highly subjective, leaving a high margin of error in purity analysis. Color measurement using the APHA color index allows these various industries to maintain safety and consistency in their products.

In beverage packaging, color goes beyond appearance, it’s an unspoken promise of quality and consistency. For one global bottling company, color variation in PET preforms and plastic caps was becoming a costly risk. A shift in shade could erode brand trust, slow production, or trigger costly rework.

That’s when they turned to HunterLab.

Struggling with color variation across sites? Request a HunterLab demo and take control of your packaging color.

Why Color Consistency is a Bottler’s Business Advantage

• Brand Integrity: Consumers recognize visual differences—even minor inconsistencies in color can influence perception and purchasing behavior.
• Process Confidence: Consistent color signals stability in formulation, additives, and processing.
• Operational Efficiency: Catching out-of-spec color in real-time prevents rework, scrap, and costly downtime.

Functional additives like oxygen scavengers further complicated color control. The challenge was clear: measure preforms and caps with accuracy, no matter the size, material, or additive load.

Customer Challenge: Varying Tools, Oversized Preforms, and Manual Workflows

This global bottler operated across multiple plants, each using different tools:

• Most relied on ColorFlex EZ for caps
• Some sites used Vista® for beverage color, with limited preform measurement

Please note: ColorFlex EZ is no longer in production. Meet the upgraded ColorFlex L2, the industry's most advanced color spectrophotometer.

But the brand’s large-format PET preforms didn’t fit standard holders, compromising measurement consistency. Additive effects on color weren’t clearly quantified, and operators selected workspaces manually, increasing variability.

⚠️ Operational Risk: Inconsistent color across production lines can mean inconsistent quality on store shelves.

Moisture can change the color of fabrics in deliberate, overt ways or create subtle color shifts nearly imperceptible to the human eye. Image Source: Pexels user snapwiresnaps.tumblr.com

The Unseen Emporium in London, England is more of a laboratory than a design house. Through a daring and innovative combination of fashion, chemistry, and digital technologies, the three masterminds behind the label work to produce dynamic clothing, accessories, and lifestyle goods that respond to their environments based on specific stimulants.1 Among their most eye-catching creations are extravagantly tailored leather jackets that change color as the humidity in the room fluctuates, the moisture level creating vivid chromatic shifts. The phenomenon of hydrochromism—color change in response to water—has heretofore primarily been intentionally implemented in the textile industry as a novelty in the form of color-changing umbrellas and swimwear. The Unseen Emporium, however, is bringing it to a new level of artistry.

But hydrochromic textiles are not a recent invention. Although deliberately moisture-sensitive dyes with dramatic color changes may be in their infancy, some level of hydrochromism is inherent to most textiles already in use today, often to the consternation of textile manufacturers.

Dark cotton fabrics will display a greater degree of color change in the presence of moisture. Image Source: Pexels user snapwiresnaps.tumblr.com

New polymer products continue to flood the market, and there seems to be no end to the continued growth in plastic manufacturing. In 2024, the global molded plastics market reached a value of $541.2 million. Experts predict a compound annual growth rate of 7.5% over the next decade, which means the market's value will surge to over $1 billion by 2034. In this booming market, competition with large manufacturers may seem daunting, yet small business continues to thrive.

To stay competitive among these giants, choosing the right spectrophotometer for plastics is often the difference in product efficiency and quality. Understanding the value of color measurement in plastic production is the first step toward optimizing growth and increasing sales overall.

Utilizing Spectrophotometric Instrumentation in Plastic Production

Modern spectrophotometers measure more than the tristimulus values captured by basic equipment. They offer spectral measurement capabilities and can quantify appearance by considering the influences of gloss and texture on perception. This technology makes them an ideal choice for many plastics, which often feature various shapes, textures, and opacities.

Sample types determine the right measurement techniques for accurate color data, so understanding these characteristics that drive your approach is the first step to utilizing your color measurement solutions. For example, accurate color quantification for transparent plastic preforms requires measuring via transmission, while opaque plastics require reflectance measurements.

The device’s geometry is also critical to ensure accurate appearance data capture. A directional 0°/45° geometry illuminates the sample at a 0° angle, with the viewing angle set at 45°. Scientific studies show that these geometric principles provide the truest representation of visual color perception.

Today’s spectrophotometers/colorimeters are available in portable, benchtop, and in-line models, designed to monitor color variations and changes in real time, from start to finish. Even slight alterations in color can be detected easily and allow for simple changes to be made at any stage of production, saving wasted materials, time, and money. These simple tools are beneficial for efficiently and effectively creating quality products and increasing sales.

Spectrophotometric Applications in Plastic Manufacturing

The variety in plastic shapes, sizes, and colors can present color measurement challenges. Nonuniformity, gloss, shape, and size can all affect color quantification, so choosing the right solution is the first step in developing consistency and quality in polymer products.

Not only are spectrophotometers/colorimeters effective for enhancing the quality and production of molded plastics, but their versatility also extends to many other areas of plastic manufacturing. For example, even nonuniform plastic pellet samples and recycled polyethylene terephthalate (rPET) can be accurately measured with this equipment. Doing so helps to ensure uniform and consistent pellet color, which is used in extrusion and injection molding and directly affects final color quality.

Other spectrophotometric applications in plastics processing include quantifying color data in:

• Opaque plastic enclosures
• Opaque plastic plaques
• Opaque plastic films
• Opaque sheet plastic
• Dark Performance plastics, such as deep blues, dark charcoal grays, indigos, and blacks
• Vinyl siding

From the beginning stages of plastic production to the final stages of color analysis in sample plaques, spectrophotometry ensures consistency throughout every step of manufacturing. The simplicity and accuracy of today’s advanced instrumentation take the guesswork out of the process, increasing both production and quality overall.