Interested in a little light reading?

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. 

Spectrophotometers are powerful solutions for objectively and scientifically quantifying color data in products. These devices capture measurements for comparison against a known scale or index to ensure goods' color falls within acceptable tolerances, supporting higher quality. Calibration is a crucial factor in ensuring the equipment delivers — and continues to provide — precise, accurate color measurements.

What Is Spectrophotometer Calibration?

Calibration of a spectrophotometer is a process for adjusting the device's sensitivity to certain wavelengths of light. This precise adjustment helps verify that the unit is measuring wavelengths as intended and quantifying color correctly. It substantially differs from standardization, a process that end users perform in their facilities.

As the ideal solution for analyzing sample color, spectrophotometers are essential equipment for quality, research, and forensic labs worldwide. These powerful devices capture critical data about a substrate's properties to help quantify or categorize it accurately. Spectrophotometers contain a spectrometer, which detects and measures wavelengths using sensors to break down the energy into its components. They also include a light source that emits energy into the sample.

Different types of spectrophotometers exist, each with distinct functions and ideal applications, including color spectrophotometers that help ensure color and appearance quality and consistency. These are specialized solutions designed exclusively to measure color within the visible spectrum between about 360 and 780 nanometers — the wavelengths of light the human eye can perceive. Color spectrophotometers come in multiple styles and employ different optical configurations to provide precise color and spectral data.

What Is a Color Spectrophotometer Used For?

Color spectrophotometers are invaluable in any application where quantifying color according to a set of numerical values is crucial to quality and product appearance. Common spectrophotometer uses and industries include the following.

Food and Beverage Manufacturing

Appearance is an important quality indicator in buying decisions, and spectrophotometers help food manufacturers ensure their products fall within acceptable color expectations to entice consumers. Color can also signify a food's suitability for safe consumption and influence perceptions of flavor, freshness, and nutrition. Food manufacturers rely on spectrophotometers to quantify chromatic data for products ranging from snack foods to dairy-based items, fruits and vegetables, and edible oils.

Color plays an equally pivotal role in beverage production, where it helps establish the commercial quality of coffee and the clarity of bottled water according to industry scales.

Plastic Manufacturing

Plastics manufacturers face unique color challenges as industry regulations evolve. Natural yellowing during virgin production calls for the use of optical brighteners to overcome. With more and more governmental mandates for higher post-consumer recycled content, finding the ideal mix to achieve the desired color repeatedly is an ongoing issue for most. Color spectrophotometers help companies in the plastics industry identify and maintain the optimal balance needed for quality, compliance, and appearance.

Chemical Processing

Samples in the chemical processing industry range from opaque powders to translucent or transparent liquids, with some being substantially costly. Accurate chemical mixing is also paramount to safety. Color spectrophotometers enable professionals in this industry to ensure quality and safety by helping identify physical properties and adhere to strict tolerances.

Other Industries

Additional industries relying on color spectrophotometers for capturing chromatic and spectral data include:

• Bio-pharmaceuticals
• Building products
• Paints and coatings
• Textiles
• Paper goods

Spectrophotometric solutions simplify the science of quantifying chromatic data for many industries. Manufacturers using a spectrophotometer benefit from higher product quality and consistency, increasing customer satisfaction. Accurately quantifying color and appearance starts with learning how to use a spectrophotometer correctly and implementing a standardized process.

1. Turn the Device on and Allow It to Warm Up

The first step in preparing a spectrophotometer for use is to turn it on and allow it to warm up so it can function correctly. Warmup times can vary depending on the model and manufacturer, but you'll generally want to wait 30 minutes. To protect the integrity of your outcomes, verify the exact time frame by consulting your owner's manual.

Modern technology has significantly changed how spectrophotometers perform compared to the early models from many decades past. These devices have become vital in global research, development and production across a broad industry range. Because multiple spectrophotometer types play different roles, choosing the correct device and selecting the optimal settings for each instrument are vital for achieving the most desirable results.