Interested in a little light reading?

Clarity is a critical aspect of liquid product quality in many industries, and modern consumers combine it with color when evaluating whether to buy a product or trust a brand. As a result, scientifically and objectively quantifying haze is essential to achieving quality goals and maintaining customer satisfaction.

What Is Haze and How Does It Alter the Appearance of Liquids?

In its simplest definition, haze is scattering of light produced by small particles in a sample. Suspended particles within a liquid also scatter light, leading to turbidity — a cloudy, milky, or opaque appearance.

Transmission haze occurs in transparent goods and liquids, like clear plastic preforms or bottled water. As light passes through the sample, factors like surface texture imperfections and impurities scatter the energy.

Primary Causes of Haze in Liquids

In liquids, a natural interaction between proteins and polyphenols usually causes measurable turbidity. Other potential causes include poor-quality raw ingredients, such as infected barley used in beer brewing or particulate residues from filtering processes.

The Importance of Haze to Consumer Perceptions

Clarity is necessary in liquids to signify quality and safety.

Turbidity in beer can be either desirable or undesirable, depending on the consumer's preference. Many manufacturers continually aim to control turbidity in beer since its presence can negatively impact taste and shorten shelf life. Others use turbidity as a competitive advantage, crafting hazy IPAs that consumers perceive as more flavorful. Similarly, some winemakers prefer haze as a marker of authenticity and a natural by-product of fermentation.

Other liquids also rely on haze to meet consumer expectations or generate a favorable customer opinion. For example, a haze in fruit juices can spur more sales by promoting the perception that nutritional value is higher. Manufacturers can create the haze naturally or use additives to produce the intended result.

If you work in the biopharmaceutical industry, you’re likely familiar with the concept of light and color measurement and the equipment used in these processes — radiometers, spectrometers, spectroradiometers, and spectrophotometers. While all four solutions are used to detect light and energy, they vary widely in their capabilities, applications, and intended purposes. It’s important to know and understand the differences between these solutions to determine which one will adequately serve your needs.

Radiometer vs. Spectrometer vs. Spectroradiometer vs. Spectrophotometer

These devices have similar names and are used to measure spectral data points and wavelengths within the electromagnetic spectrum. Despite this similarity, they have varying scopes regarding the types and qualities of measurements they produce.

Radiometers can only detect and measure electromagnetic radiation within a particular wavelength range. Spectrometers measure a broader scale of electromagnetic energy and have more capabilities, including breaking down signals based on amplitude.

In comparing spectroradiometers vs. spectrometers, the main difference is that spectroradiometers combine the capabilities of radiometers and spectrometers. These devices also collect details about power, radiance, and other metrics.

Spectrophotometers measure light reflected or transmitted by objects, while radiometers measure light emitted by a light source. Unlike the other tools, spectrophotometers focus on how transmitted and reflected light generates color rather than on the qualities of the light itself.

What Is a Radiometer?

A radiometer measures the electromagnetic energy present in a specific wavelength range. This solution is typically used to detect and quantify energy outside the visible light spectrum and measure infrared and ultraviolet light. The radiometer begins by measuring the incoming current or voltage in watts, then corrects the signal to create a calibrated, quantitative light level measurement. With this information, the meter provides one reading over the specific wavelength range it is designed to measure.

Pros and Cons of Radiometer

Radiometers are inexpensive and portable, making them a cost-effective and practical choice. This solution can identify troublesome UV energy and detect and measure heat energy on surfaces. It also has one sensor that allows it to quickly measure all intended wavelengths.

However, radiometers cannot identify emitted wavelengths or their individual amplitude. Sometimes, variations exist in the filter used to match the light source, which creates difficulty when comparing results from radiometers of different manufacturers. Also, radiometers only measure a particular range of wavelengths, unlike other tools. 

Applications

Radiometers' ability to detect the presence of UV energy makes them valuable tools for any application where it is undesirable, such as museum lighting. In this atmosphere, UV energy could degrade artifacts or artwork.

The device also measures infrared light, enabling surface temperature measurements in settings such as along an assembly line or on a road's surface. Other applications include monitoring weather, like precipitation and wind speeds.

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.

Every material absorbs, reflects, or transmits light, which determines the color we see when looking at an object. Transmission refers to the light waves that pass through a translucent or transparent sample, and spectrophotometers provide quantitative measurements of that data. These devices make it possible to evaluate a sample's color scientifically and objectively, which is vital for ensuring color consistency in various applications. Spectrophotometer transmittance measurements enable better quality control and enhanced consumer perception of your products.

What Is Transmittance in a Spectrophotometer?

The definition of transmittance is the measured light that passes through a sample, meaning the light that is not absorbed or reflected. Three primary transmittance measurements include:

• Diffuse transmittance (Td, n): This measurement is the ratio of the flux transmitted by a specimen to the incident flux, with the transmitted flux being measured at all forward angles except the regular transmission angle. When light is diffusely transmitted, its direction changes as it passes through the material, causing scattering.
• Regular transmittance (tr, n): This measurement is the ratio of undiffused transmitted flux to incident flux. In other words, it is straight-through light.
• Total transmittance (tt, n): This measurement is the ratio of the flux transmitted at all forward angles to the incident flux. Total transmittance is the sum of regular transmittance and diffuse transmission.

These values are essential to maintaining quality in products like beverages and edible oils. It's best to measure color with a spectrophotometer to capture more accurate information, as these devices provide exact quantitative data regarding the amount of light that passes through a sample. 

The transmittance formula is:

T = PT/P0

The values in this formula represent:

• T: Transmittance
• PT: The source's radiation power as it exits the sample
• P0: The source's radiation power as it enters the sample

The resulting calculation is a ratio, comparing the light before it enters the sample to the light after it passes through it. A value closer to 1 means most light passes through, while lower values mean that less light passes through. 

What Is Percent Transmittance in a Spectrophotometer?

Percent transmittance displays the light that passes through the sample as a percentage rather than the ratio created by the above formula. You can get the value by multiplying the ratio by 100. 

A sample with 100% transmittance is transparent, allowing all light to pass through. Lower numbers indicate more translucence than transparency. At least 30% of the light must pass through the material for effective transmittance measurements.

The transmission percentage is also helpful for absorbance calculations. A commonly used absorbance formula is:

A = 2-log10(%T)

This formula determines the amount of light absorbed using the percentage of light that passes through the sample. 

Powders play a vital role in many industries, from food products like cocoa powder to minerals and the lifesaving medications pharmaceutical manufacturers create. Their colors must be consistent and meet customer expectations to support quality initiatives, conformance with industry standards, satisfaction, and, ultimately, profitability. Spectrophotometers provide the easiest, fastest, and most objective way to quantify color to help you reach these goals. 

Key Features to Evaluate

Learning what key features to evaluate as you explore the spectrophotometric solutions available can help you make a more sound investment.

Minimum Sample Sizes

Some ingredients, like certain high-value spices and active pharmaceutical components, are incredibly expensive. Reducing the size of the sample needed for accurate measurements is key to controlling waste and limiting sampling costs. A spectrophotometer that offers the smallest sample size possible will deliver the most value for many applications and significantly lessen the expenses involved with high-value powder production.

Sample Compatibility

Powders present unique challenges in color measurement. Many have nonuniform textures and varying particulate sizes requiring careful sample preparation to promote accurate outcomes. Their opacity demands specialized optical geometry that captures data through reflectance. A thorough, careful analysis of your powder's physical properties will help ensure the spectrophotometer's capabilities align with your needs.

Index and Scale Library

Many industries have specific industry scales or indices they use to ensure their products conform to standards. Samples may rely on different color spaces, such as the CIELAB scale often used to measure barium sulfate. Evaluate the spectrophotometers you're considering to ensure they're capable of providing data within the scales that apply to your industry.

Effective Bandwidth

Regardless of which wavelength you measure in the visible spectrum, you need to ensure the device you select has suitable effective bandwidth for accuracy. This term refers to the range of wavelengths interacting with a sample at a given moment. A narrow effective bandwidth coupled with high radiation throughput helps ensure strong signals and background noise reduction. This configuration allows for more precise readouts since the spectrophotometer can isolate smaller wavelength ranges.

Integration Capabilities

Ideally, the spectrophotometric solution you choose should fit effortlessly into existing workflows instead of forcing you to adapt proven processes. Features like universal compatibility simplify integration. This trait allows the spectrophotometer to connect to and communicate seamlessly with other devices. In addition, selecting a model with many connectivity options makes data export and transfer to your quality management systems fast and easy.

Viewing Area

While finer powders may lend themselves to a smooth, even sample surface, sample averaging is critical for measuring color in powders with larger particles and nonuniform characteristics. These traits can lead to shadowing that can create measurement discrepancies when only capturing data in one reading. Taking multiple measurements across larger viewing areas and averaging them helps resolve those challenges, so it's essential to consider viewing area size as you narrow down the options.

Plastic plaques play a crucial role in evaluating the color and appearance of plastic pellets, serving as a reliable medium to transform raw materials into a tangible, uniform surface for precise analysis. These plaques are pressed under controlled conditions, allowing manufacturers to assess how the pellets' color manifests when formed into a flat, consistent shape. To further enhance their utility, plaques can be produced with varying surface characteristics, such as different gloss levels and textures, to evaluate the visual impact of these properties on color perception. This process ensures that the final product meets both aesthetic and functional requirements, providing a critical quality check in industries where appearance consistency is paramount, such as automotive, consumer goods, and packaging.

Opacity and Color Measurement

Opacity refers to a material's ability to prevent light from passing through. When measuring color in opaque materials, we focus on reflectance. Reflectance is how light interacts with the plastic's surface and reflects to our eyes. Visual color comparisons are unreliable due to limitations in human color perception and the inability to account for texture variations. Spectrophotometers can standardize conditions to ensure the measurement is consistent and repeatable.

Spectrophotometers are invaluable to many industries, ranging from the food to plastics industries and beyond, delivering the color consistency necessary to streamline supply chain efficiencies and maximize product quality. The key to ensuring reliable performance and color measurement quality is knowing how to properly maintain a spectrophotometer.

What Is the Function of a Spectrophotometer?

A spectrophotometer scientifically measures the color of materials using a light source, wavelength-selective optics, sensors, and software to convert emitted energy to an industry-standard color scale. This measurement enables companies to verify the quality and consistency of their products, ingredients, and raw materials. The device mimics how the human eye sees color but eliminates error-prone manual visual observations for higher accuracy.

Best Practices for Using and Taking Care of Your Spectrophotometer

Spectrophotometers must undergo the proper routine maintenance to deliver the most precise and accurate measurements. With the right standardization and care, you can ensure your color spectrophotometer performs at its best.

1. Perform Routine Maintenance

A well-maintained device provides the most accurate and reliable readings. Maintenance begins with a thorough cleaning. No matter how well-calibrated your device is, it won’t deliver accurate or consistent readings if it isn’t clean. That’s why it’s vital to ensure your spectrophotometer is free of dirt, dust, grime, and other contaminants that can obscure measurement results.

When cleaning your equipment, it’s crucial to follow the best practices outlined in your user manual to avoid damaging the device and invalidating your warranty. Avoid using any harsh or abrasive tools or substances when cleaning your spectrophotometer.

Cleaning frequency varies based on the components. The exterior of the sensor and mounting generally require weekly cleaning. If your work involves messy samples that contact the sensor, you may also have to clean between measurements.

You should also consider your environment when determining cleaning frequency. For example, a unit stored in a dusty, poorly ventilated closet will require more routine cleanings than one contained in an air-conditioned office.

Other routine maintenance checks include:

• Inspecting and cleaning the power cord
• Verifying the optics are clean and in good condition
• Testing general structures like the device touch screen or buttons

Beyond these general checks, each model operates differently. Check the owner's manual for additional maintenance procedures specific to the device.