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Polyethylene terephthalate (PET) preforms are essential to attractive, durable packaging for industries like beverage manufacturing, edible oils, and more. As the market continues to grow, so does the need to accurately and objectively quantify appearance to uphold product quality. Spectrophotometry is the best solution for scientific color measurement, eliminating the error-prone nature of manual visual assessment for higher confidence and precise data. Explore why color matters in preforms, the challenges of color consistency, and the ideal equipment for measurement to ensure high-quality results.

Why Color Matters for Plastic Preforms

Color plays an instrumental part in conforming to standards, protecting products, and influencing consumers.

Industry Standards

Plastic preform color is vital in meeting industry-specific standards. Sectors like pharmaceuticals and beverages often have strict color tolerances to ensure safety, traceability, and regulatory compliance. For example, specific packaging colors may indicate the presence of certain additives or differentiate between product formulations. Adhering to these color standards helps uphold product integrity and consumer safety.

Product Protection

Some goods, such as certain pharmaceuticals and beverages, are sensitive to ultraviolet (UV) light. Ongoing exposure to UV rays can cause degradation, affecting visual appeal, medical efficacy, safety, or taste. Opaque plastic packaging forms a shield against UV light, helping protect the product within against excess exposure. Inconsistent color may signal uneven distribution of colorants or UV-blocking additives, potentially increasing the chances of UV rays penetrating the packaging.

Quality Perception

Products like edible oils and beverages compete in crowded marketplaces. As a result, standing out on the shelves is key to your success. The plastic colors you choose help attract attention and reinforce your branding with consumers. When your color remains consistent and appealing, it indicates your commitment to quality and meeting your customers' expectations. Conversely, color alterations can signify issues with your quality control or manufacturing processes, causing consumers to reach for a competitor's product instead.

Modern consumers have endless opportunities to choose products from your competition. Product consistency matters, and a visual inspection is no longer enough to gauge it. To appeal to the most discerning customers, your products need a precise, uniform appearance — and you need an accurate color measurement tool to ensure that's the case.

The Benefits of Spectrophotometers

Spectrophotometers measure light transmittance or reflectance from plastics, foods, drinks, and other materials. They eliminate the guesswork of visual evaluations and variable observation conditions, such as lighting, that affect the way we see color.

Using a spectrophotometer enhances a brand's identity by associating specific colors with its products. Inconsistent coloring can confuse consumers, leaving them more likely to choose a competitor's option over yours. The more consistent your products are, the more likely a consumer is to stay committed to your brand.

Consistent quality and aesthetics are paramount in the competitive world of building materials. For vinyl siding manufacturers, achieving consistent color across production batches is crucial for customer satisfaction and brand reputation. 

Here at HunterLab, we offer state-of-the-art spectrophotometers, advanced quality control software and expert techniques to help you maintain color consistency throughout your vinyl siding production processes.

Understanding the Challenges of Measuring the Color of Vinyl Siding 

Even slight color variations can lead to rejections, returns, and lost revenue. Visually assessing vinyl siding is not enough to achieve accurate, repeatable results and can lead to mismatched siding panels.

Measuring the color of vinyl siding presents unique challenges compared to other materials. Some of these challenges include:

• Texture variations: Vinyl siding often has a textured surface that can affect light interaction. HunterLab's spectrophotometers have advanced features that can compensate for surface texture variations. They ensure accurate readings regardless of the siding's texture.
• Large panel sizes: Larger panels magnify any variation in the manufacturing process, from raw material differences to pigment distribution and alterations occurring in storage. A spectrophotometer accurately quantifies color at every stage to help ensure consistent, precise results.

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.

Plastic manufacturing has grown significantly since the 1950s, surpassing that of any other material. Today, plastics see use in markets ranging from automotive to goods packaging to food and beverage production. Plastic color is and will continue to be pivotal as the primary determinant by which consumers judge product quality and desirability, yet accurately quantifying it comes with unique challenges.

Common Challenges in Plastic Color Measurement

Typical plastic color measurement challenges include the following.

Natural Yellowing

Virgin plastic resins naturally yellow during processing as a result of oxidation. Additional yellowing can occur with age or exposure to ultraviolet rays. To achieve clear or almost clear end products, manufacturers must add optical brighteners that fluoresce on the blue side of the visible spectrum to negate the yellowness. That translates into almost all plastic goods containing at least some percentage of optical brighteners. As a result, these materials inherently fluoresce and introduce more complexity to achieving the desired clarity and visual chromatic qualities.

Regulatory Pressures

Government entities worldwide are passing ever-stricter regulations on the percentage of post-consumer recycled plastic that must be used in new plastic production to prioritize a more circular economy. An increase in the amount of recycled plastic used causes a corresponding rise in the amount of optical brighteners and other additives in feedstock that manufacturers must adjust for.

These challenges make accurate color measurements even more pivotal since one variation in the input can substantially impact the outcomes.

ESG Initiatives

In addition to governmental action, modern plastics manufacturers are feeling similar pressures from their stakeholders. Consumers, employees, and investors alike increasingly call for more sustainable practices and transparency in environmental impact.

To account for these pressures, many companies enact Environmental, Social, and Governance (ESG) initiatives that help achieve the six principles of a more circular economy. These pillars include minimizing waste, maximizing resources, saving energy, and reducing carbon footprint.

How to Resolve Color Measurement Challenges in Plastics

Fortunately, there are several steps you can take to resolve color measurement challenges with plastics production.

The use of plastic bottles in liquid packaging first became popular in the 1950s and 1960s. Today, plastic's cost-effectiveness, durability and recyclability have made it the go-to material for bottles among most major companies. Throughout the manufacturing of these bottles, it is vital that processors maintain accurate coloration. Any product entering the sales market should be uniform and consistent, down to the label and the packaging. This level of precision calls for specialized tools — and HunterLab provides them.

The Power of Spectrophotometers 

When you need to measure the color of plastic bottles, spectrophotometers offer the most objective and precise results. A spectrophotometer measures how light reflects off the bottle and uses those measurements to produce a numerical value in line with some of the most well-known color indices. 

Spectrophotometers make it easy for any brand to streamline its coloration practices and increase product consistency. Their use can translate to major benefits in:

• Brand identity: Plastic bottles can be manufactured in almost any color, so many brands produce their bottles using a unique pigment combination to set them apart. Coloring bottles consistently allows you to establish your own look that consumers will begin to recognize over time, even before they see the label.

• Consumer satisfaction: Changes in any part of your product or its packaging — including a significant color departure — can signal to loyal consumers that your product has changed in some way. By keeping your colors consistent, you can put consumers at ease and ensure they stay with your brand instead of choosing a competitor. 

The Yellowness Index from ASTM International provides a measurable standard for assessing the yellowness in white or light-colored materials, such as plastics. This standard determines the degree of yellowness present, allowing companies to perform quality control processes to maintain product consistency. The test uses a spectrophotometer to quantify the color measurement.

The APHA color system is the most common measurement scale for measuring yellowness in liquids. It serves industries ranging from chemical production to pharmaceutical development.

Materials That Require Yellowness Observations

Various plastics require yellowness observations due to the changes these materials undergo in processing. These plastics include:

• Polyvinyl chloride (PVC)
• Polycarbonate (PC)
• Purified terephthalic acid (PTA)
• Polyethylene terephthalate (PET)

Yellowness appears in PET due to oxidation. With the increasing use of recycled PET (rPET), manufacturers must measure color to counter yellowness and determine the correct ratio of optical brighteners required to mitigate it.

What Is the Yellowness Index?

The Yellowness Index (YI) measures yellowness due to product changes. The ASTM E313 Yellowness Index is the most common method for determining yellowness in materials like plastics. The standard gives defined indices for measuring the shift from ideal white. It is calculated according to the following formula:

YI = (100CxX - CzZ)/Y

The X, Y, and Z variables are CIE Tristimulus values, which express color and how it is perceived. Cx and Cz depend on the illuminant and observer. During calculations, users choose the values for these coefficients from a table to correspond with spectrophotometer settings. The ASTM E313 combines the calculations into a single value, defining the yellowness amount in a sample. The lower the number, the less yellow the material is.

The YI value is commonly reported as the difference in yellowness between a product sample and the original or reference, designated as delta YI (∆YI).