Loose Powder Color Measurement: Challenges and Solutions

Analyzing loose powder hues comes with unique challenges due to the innate qualities of the powders.

Spring is a time of rebirth and regeneration when color returns to our world vividly after the grays and whites of winter. And perhaps there is no better expression of this than the Hindu celebration of Holi, also known as the festival of colors.

Each spring, people around the world — Hindu, and non-Hindu alike — mark the coming of the season in a brilliant display of colorful powders thrown in the air and streaked across revelers. This colored powder is essential to the celebrations, originating with the legend of the Hindu deity Krishna who colored his lover’s face to match his own blue skin.

Today, four primary powder colors are used during the festival, each representing a unique aspect of the Holi celebration. Green signifies spring's new beginnings, blue symbolizes the connection to Krishna, red stands for fertility and love, and yellow evokes health and happiness. 

Traditionally, these hues were created using real turmeric, flower extracts, and sandalwood paste. Now, however, they are largely produced using artificial colorants. This practice has led to health and environmental concerns after reports that hazardous materials like chromium and lead were used in powder production. These chemicals can cause pollution and health issues like eye and skin irritation or respiratory illnesses.

As a result, a number of commercial powder suppliers have recently returned to more natural and plant-based color sources. In order to promote safer, more eco-friendly products, however, powder suppliers must ensure that their powders accurately reproduce the vivacious colors we have become accustomed to. This is vital in order to allow customers to obtain healthier products without compromising appearance. This requires careful monitoring of color behavior throughout the production process.

Reflectance spectrophotometers are ideal for measuring the color of all types of loose powders, regardless of their end use. Using a 45°/0° geometry, these spectrophotometers mimic the way the human eye sees color, only better. Without the impact of outside interferences, spectrophotometric devices are able to objectively analyze samples for the highest level of accuracy and repeatability. As such, they serve a critical role in the development and production of loose powders across industries, from cosmetics to pharmaceuticals. However, there are a number of special considerations for loose powder color measurement that must be kept in mind during the analytical process.

The Challenges of Loose Powder Color Measurement

Loose powders present unique challenges to the color measurement process as a result of their inherently textured and nonuniform characteristics. Due to their particulate form, these powders are susceptible to light trapping, shadowing, and ambient light interference, opening the door to inaccurate and inconsistent analysis. As such, it is not possible to measure loose powders as-is. Instead, they must be carefully prepared and measured through the side of a clear glass sample cell in order to be effectively made into a solid.

The preparation demands of loose powders make them particularly vulnerable to operator inconsistencies. It is vital to employ the same preparation and measurement techniques each time a sample is analyzed to eliminate variation and ensure batch-to-batch accuracy. To facilitate consistency, choosing a highly accurate yet user-friendly spectrophotometer that minimizes the possibility of human error is imperative. Additionally, some powders may exhibit a degree of fluorescence, making them vulnerable to any UV content in the light source and requiring the use of a device with a UV control option.

Sample Averaging: A Simple Solution

When working with loose powders, sample averaging is often an essential part of the process, allowing you to overcome texture and size variations via simple measurement protocols. Fine powders may allow you to create a smooth, uniform surface within the sample cell capable of being analyzed in a single measurement. However, samples with larger or irregular particles can suffer from shadowing even within the sample cell, compromising the ability of the spectrophotometer to capture accurate color information in a single reading.

In these cases, averaging the results of multiple measurements, or sample averaging, can compensate for these particulate qualities. The easiest way to accomplish this is by rotating the sample, gently agitating it to redistribute the particles, or evaluating multiple samples from the same batch. Doing so enables you to capture more measurements, which contributes to seeing more accurate results. The exact number of measurements depends on the nature of the powder and your own tolerance.

Small samples of loose powders may require special sample cells to ensure accurate measurement. Image Source: Flickr user Kurtis Garbutt

Working With Small Samples

When working with scarce, hazardous, or expensive powdered materials, minimizing sample size may be preferable or even necessary. However, these conditions also demand highly reliable color measurement to ensure no materials are wasted or used unnecessarily as the result of an inaccurate analysis. Due to the challenges inherent to powders, it is particularly important to choose both a high-quality spectrophotometer and appropriate sample preparation methods. This includes selecting the appropriate sample cell when analyzing small powder samples. 

HunterLab’s semimicro powder sample accessory, paired with our specialized SAV port plate, is the perfect solution for small sample powder measurement. Designed specifically to analyze small quantities, this apparatus allows you to consistently arrange powdered materials in the densities and heights necessary for accurate analysis of samples as small as 0.4cc. This facilitates precise capturing of color data while preserving materials or limiting operator exposure to harmful substances.

ColorFlex L2 Is the Most Powerful Spectrophotometer for Powder Color Measurement Yet

ColorFlex L2 is the newest innovation from the chromatic science experts at HunterLab. We've designed it to meet the demands of modern color measurement in powders and deliver unmatched value. This spectrophotometer helps you take your quality assurance to the next level. Achieve consistency, reduce waste, and boost efficiency with:

• Immediate impact: ColorFlex L2 is ready to integrate into your color workflows right out of the box. A built-in wizard guides users quickly through setup and operation, drastically reducing implementation and training times.
• Unparalleled accuracy: The ColorFlex L2 uses 45°/0° directional geometry to provide accurate color and spectral data. A precision camera ensures correct sample positioning to help eliminate errors and discrepancies for superior confidence in outcomes.
• Enhanced connectivity: HDMI and USB connectivity makes data export to laboratory information management and statistical process control systems fast and easy.
• Exceptional versatility: ColorFlex L2 features our Essentials 2.0 software and requires no additional computer, making it ideal for implementation in labs or on the production floor. We've also included the largest library of color scales and indices for comparison, plus the ability to configure custom tolerances.
• Universal compatibility: We've engineered this spectrophotometer for universal compatibility with other essential equipment, so you can quickly standardize and share data across facilities and devices.
• Built-in UV control: ColorFlex L2 comes with factory calibration for UV control to deliver accurate measurements on samples with optical brighteners or fluorescent properties.
• Instant feedback: A light indicator immediately provides pass/fail feedback.

HunterLab Quality

HunterLab has been a leader in the field of color measurement for over 70 years. Our innovative range of spectrophotometers, accessories, and software packages give our customers extraordinary insight and control over their products throughout the manufacturing process, even in the most challenging conditions. Whether you are working with large or small samples, solids, powders, or liquids, we have the tools you need to rapidly capture and analyze color data in a way that makes sense for your organization.

Contact us to learn more about our renowned range of spectrophotometers and let us help you select the ideal model for your purposes.