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Both benchtop and portable spectrophotometers have vital industrial applications. These devices facilitate manufacturing color-quality testing and many other industrial processes. Depending on your industry and operational needs, you may need to use each device for different field sites. You’ll need to consider whether convenience or repeatability is your top priority for specific applications.

If you’re weighing the benefits of one versus the other, let us walk you through a comparative guide. We’ll explore the advantages, disadvantages, and differences between benchtop and portable spectrophotometers so you can choose the best option for your applications.

Benchtop Spectrophotometers

Benchtop spectrophotometers offer extremely high precision and consistency for stringent quality control measurements. Professionals across many demanding industries rely on these devices to address critical color measurement needs.

Benefits of Benchtop Spectrophotometers

With benchtop spectrophotometers, you can gain many key advantages, including:

• Dual use capabilities: Portable spectrophotometers are designed for reflectance measurements only, while many benchtop models offer both reflectance and transmittance measurement capabilities.
• Expanded wavelengths: Portable spectrophotometers are often limited in wavelength capabilities, measuring in the visible wavelengths with some offering limited UV capabilities. Many benchtop units offer expanded capabilities in the UV, visible, and IR wavelength ranges.
• Data output: Benchtop spectrophotometers offer more sophisticated and modern interconnectivity to LMS, SPC and other data management systems.
• Sample handling: Benchtop spectrophotometers provide a wide range of sample handling solutions to maximize accuracy and repeatability.
• Maximum accuracy: While all spectrophotometers offer exceptional precision, benchtop options typically feature maximum accuracy for applications with very tight color tolerances.

Drawbacks of Benchtop Spectrophotometers

When you’re creating quality standards or trying to ensure consistency across multiple locations, a benchtop device may be best for the job. However, outside of these applications, benchtop spectrophotometers come with disadvantages.

These options lack portability, so you must transport items to the benchtop spectrophotometer’s location instead of carrying a hand-held model throughout the facility. That can result in lost productivity. Additionally, benchtop options are generally more expensive than portable spectrophotometers.

Sealants are critical for protecting natural stone finishes, such as marble countertops. Image Source: Shutterstock user Jodie Johnson

The color and clarity of natural stone sealants play an important role in not only protecting the surface of the stone, but creating aesthetic appeal. Indeed, while designers often spend significant time carefully choosing a stone, the final appearance of their project is highly dependent on the quality of the sealant; unwanted color variations or issues with clarity can drastically alter the final appearance of the stone, preventing the designer from realizing their vision. As such, manufacturers must closely monitor the color and clarity of sealants to guarantee that their products behave as expected. Today, breakthroughs in color measurement technology are making this process more simple than ever before, helping sealant manufacturers enhance the quality of their products while optimizing overall efficiency.

Hair gloss treatments offer an effective new way to repair damaged hair and add a youthful appearance to dull locks, yet without proper haze and color measurement, many formulations fall short in creating the appearance that consumers desire. While harsh permanent dyes open the hair shaft to remove natural hair pigments and insert new color pigments, hair gloss provides a protective coating to the outer layer of the hair follicle to improve both color and shine. This coating must be developed to either match or enhance the existing color by providing a clear coating which maintains the proper reflectance and color values. Color measurement instrumentation that monitors both color and haze is therefore essential for developing a high-quality hair care product.

Whether creating a color matching formulation or a clear gloss treatment, understanding the relationship between color and haze and monitoring both can improve the production and quality of the product. While hair gloss coatings are designed to give hair a healthy shine and improve the reflective quality, contamination and formulation errors often lead to a cloudy or hazy appearance, translating to dull hair. Since the cloudy or hazy appearance of the product is often undetectable to the human eye and only recognizable after application, spectrophotometric analysis is critical during the formulation process.

Developing hair gloss products is both an art and a science, which requires the right color measurement technology to ensure proper transparency and predictable results. Spectrophotometers that are designed to measure both transmission color and haze provide the data needed to ensure proper formulation and meet the quality standards consumers demand. Now, simultaneous color and haze measurement is expanding the possibilities for quality control in the hair care industry.

The color of a beverage will have a direct impact on how consumers perceive the product. Image source: Ben Kolde on Unsplash

Functional beverages—like energy and nutraceutical drinks—are growing in popularity among consumers who need a boost of energy, add more vitamins and minerals to their diets, or address specific health concerns. Based on a recent report from Transparency Market Research, “Global market for functional drinks is observing a healthy rise in its valuation, thanks to increasing awareness about the benefits of functional drinks on health and wellness.”1 As a result, many beverage manufacturers are both introducing new products and altering existing products to align with changing consumer habits. However, as brands change their recipes to meet functional demands, they must consider the impact of color change and its effect on consumer perception.

The ingredients in functional beverages, as well as the carbonation, can change the overall color of the drinks. Even beverage manufacturers that create translucent products need to consider the impact of color. For example, if a consumer is expecting a clear product, they may be turned off if the product appears cloudy or murky. which can be an indication of impurities. Spectrophotometric technology can be used to ensure your beverage’s color and haze remains consistent even as recipes change

The human eye can see millions of colors. However, it won’t always distinguish colors from one another accurately. You may perceive two slightly different colors as the same or see differences in objects of identical color depending on your viewing angle and lighting. This creates challenges when communicating about color. This inability to precisely identify and communicate color can be troublesome for designers or manufacturers when seeking to replicate color standards and establish color discrepancies.

To reproduce an exact desired color every time, manufacturers and designers need ways to quantify a color's properties and determine the numerical difference between colors. CIELAB or CIE L*a*b* is a device-independent, 3D color space for precisely measuring and comparing all perceptible colors utilizing three color values. In this color space, numerical disparities between values represent the degree of color change humans can perceive.

CIELAB's core design and operational assumption are founded on scientific theory, which shows that the brain interprets retinal color inputs as differences between light and dark (lightness) and between mutually exclusive zones of opposing colors: red/green and blue/yellow. We call this the "principle of color opposition correlation" since color cannot be red and green, or yellow and blue. Have you ever seen a greenish-red?

What Is CIELAB Color Model?

The L,a,b color space was originally defined in 1948 by Richard S. Hunter, the founder of HunterLab. It was designed to be computed via simple formulas from the CIE 1931 XYZ color space, but to be more perceptually uniform. Hunter named his coordinates L, a, b, and this was the precursor to CIELAB, created in 1976 by the International Commission on Illumination (CIE). The CIE in CIELAB is the abbreviation for the International Commission on Illumination's French name, Commission Internationale de l'Eclairage which named the coordinates for CIELAB as L*, a*, b* to distinguish them from Hunter's coordinates.

Hunter L, a, b and CIE 1976 L*a*b* (CIELAB) are both color scales based on the Opponent-Color Theory which assumes that the receptors in the human eye perceive color as the following pairs of opposite:

• L scale: Light vs. dark where a low number (0-50) indicates dark, and a high number (51-100) indicates light.
• a scale: Red vs. green where a positive number indicates red, and a negative number indicates green.
• b scale: Yellow vs. blue where a positive number indicates yellow, and a negative number indicates blue

The perfect color scale would be uniform throughout color space, meaning that a difference of one unit between two colors would appear to be visually different by the same amount whether red, purple, orange, or blue. In truth, neither Hunter L, a, b nor CIELAB is perfectly uniform. Both the Hunter L, a, b and CIE L*,a*,b* scales are mathematically derived from CIE XYZ values, however, Hunter L,a,b uses a square root function which contracts in the yellow region of color space and expands in the blue region, while CIE L*,a*,b* uses a cube root function and is over expanded in the yellow region.

In general, the Hunter L,a,b and CIELAB (L*,a*,b*) color scales are perfectly acceptable and descriptive for color measurement and to define color tolerance standards, though The CIELAB scale generally gives better approximation to visual evaluation of color difference for very dark colors. Both of these scales are intuitive, and their use with practice can easily lead to understanding and communication of color values.

Spectrophotometers measure light’s wavelength distribution by providing the percentage of reflectance from an object, detecting the color of the sample. There are two types of beam spectrophotometers — single beam spectrophotometers and double beam spectrophotometers. These instruments have several key differences you should keep in mind when deciding which is best for your laboratory.

Single Beam Spectrophotometer

Single beam spectrophotometers determine color by measuring the intensity of the light sources before versus after a test sample is inserted. This light source is modulated (turned on and off) to differentiate the light coming from the light source versus the light coming from the flame.

The single light beam passes through the sample, and the single beam spectrophotometer measures the intensity of the light reflected from the reference to measure the sample.

Double Beam Spectrophotometer

Double beam spectrophotometers measure color in a sample by using two, or “double,” beams. One beam passes through the sample side, and the other beam passes through the reference side, so the reference and the sample can be read simultaneously with no need to recalibrate the instrument.

Per Section 6.2 of ASTM D1209 Standard Test Method for Color of Clear Liquids (Platinum Cobalt Scale)

“When properly sealed and stored the standards are stable for at least a year and do not degrade markedly for 2 years.”

Our industrial experience is that if kept properly stoppered in amber bottles, the APHA/Pt-Co/Hazen visual color standards do not degrade significantly for longer than 2 years but this is the time frame that most sources reference as optimal.

If you have a dated APHA/Pt-Co/Hazen 500 liquid color standard, one validation method would be to see if it still meets the absorbance tolerance limits of ASTM D1209 Table 1, and is effectively clear (ASTM D1003 Haze% < 2).

A literature reference on stability of the APHA/Pt-Co/Hazen color standards can be found at:

Scharf, W. W., Ferber, K. H., and White, R. G., “Stability of Platinum-Cobalt Color Standards,” Materials Research and Standards, Vol. 6, No 6, June 1966 pp 302-304.