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Spectrophotometers measure light through wavelength distribution, and scientists use these instruments to measure different types of light, including visible and near-ultraviolet. Scientists wanted to obtain these measurements at a higher speed and resolution, and the double beam spectrophotometer meets this need.

Understanding Double Beam Spectrophotometers

A double beam spectrophotometer is an instrument that determines the absorption of light in liquid or gas samples in graduated cylinders. Its components are:

• Monochromator
• Detector
• Light source
• Interpreter
• Sample holder

This instrument is called a “double beam” spectrophotometer because it uses two beams of light:

• Reference beam: This beam passes through the reference standard to monitor the lamp energy.
• Sample beam: This beam passes through the sample to reflect sample absorption.

Double beam spectrophotometer diagrams show how the mechanical chopper divides the energy from the light source using a half mirror, so one beam goes to the reference side, and the other beam goes to the sample side. This format allows the reference and the sample to be read simultaneously for a real-time reference. The double beam spectrophotometer uses an infrared thermometer and photometers to measure absorbance versus wavelength to detect the color of the sample. The absorbance measurement is the ratio of the sample to the reference beams.

Modern spectrophotometers use a broad spectrum of electromagnetic wavelengths in their reflection and transmission processes. This includes visible and near-ultraviolet rays, as well as infrared and microwave rays.

Light intensity is crucial to the spectrophotometer’s function, which explains why the device’s lamp must be reliable and capable of emitting strong beams. These light beams may differ depending on the type of wavelength being measured. This ultimately helps scientists determine how a sample interacts with light across varying wavelengths.

Advantages of a Double Beam Spectrophotometer

Raw sugar has a high color value and must go through refinement and purification before consumption. The International Commission for Uniform Methods of Sugar Analysis (ICUMSA) has several methods for the colorimetric determination of sugar at a known concentration, also called the Brix value. By measuring the color with the ICUMSA color chart, you can ensure consistency and understand the value of your product.

Why Measure Sugar Color?

Color is an indication of freshness and quality in many foods, including sugar. The sugar color chart measures the amount of yellow in the sugar. This color indicates residual molasses that was not removed during the refining process. There are several reasons to measure sugar color. By doing so, you can:

• Improve refining processes: The sugar color is the result of the steps of the manufacturing process, so this data can help monitor and control sugar refining.
• Add more visual appeal: Sugar color is appealing to consumers, and consistent color is key to product sales.
• Produce better quality food products: The color of sugar is indicative of its quality, and its quality will go on to impact that of any food made with it.

What Is the ICUMSA Method?

The ICUMSA color scale determines the solution color of raw sugars, brown sugars, white sugars and colored syrups as well as the decolorization of glucose syrups. It is an indication of how much residual molasses was left behind during the refining process. The more processing steps the sugar goes through, the more color is removed. Raw sugar is dark brown, and highly refined sugar is white.

Consumers are demanding more natural, healthier food virtually across the board and the condiment industry is no exception. The ketchup segment of that accounts for more than $8 billion annually, with the vast majority of ketchup consumption happening in North America.1  Despite this high figure, the market is declining due in part to increased awareness of the risks of preservatives and high sugar typically present in the popular condiment. As manufacturers seek out ways to increase the appeal of ketchup by eliminating these additives, they may need to adjust their formulas to account for color.

Ketchup, however, can be a surprisingly finicky condiment when it comes to color integrity. Everything from the shade of the tomato to cooking duration and temperature could result in an undesirable color, which is either too dark or too pale. As manufacturers adjust their ingredients, the need to find ways to ensure ketchup color is still visually appealing to consumers remains. Using spectrophotometers in the process of creating ketchup is an ideal solution.

Click here for the best spectrophotometer to measure ketchup color

Accuracy and efficiency are crucial in the realm of color measurement. With non-contact spectrophotometry, you can optimize instrument performance and precision, leading to accurate results for even the most challenging samples.

What Is Non-Contact Spectrophotometry?

Non-contact spectrophotometry combines spectrophotometry with color imaging procedures to characterize highly complex materials. Like standard spectrophotometry, non-contact spectrophotometry facilitates the quantitative measurement of light absorption over a range of wavelengths to measure the color of a sample. However, this particular technique accomplishes this task without touching the sample surface, facilitating irregular sample measurement with greater accuracy and efficiency.

When analyzing a surface, keep in mind that texture influences how color is perceived. High gloss surfaces obscure color, and changing this texture to something more matte can change how the color looks. Since color measurement with a spectrophotometer involves shining light onto the surface and measuring reflectance, special considerations must be made about evaluating color and appearance (SPEX) or color alone (SPIN) with gloss.

Understanding Gloss Measurements

Gloss is a surface attribute that creates a shiny, metallic appearance. This visual perception appears when the surface is elevated and exposed to direct light. Gloss measurements are taken with a glossmeter that determines specular reflection (gloss) by measuring the amount of reflected light at an equal and opposite angle.
Knowing how to measure the color of a gloss depends on the surface type. For coatings, plastics and other nonmetal surfaces, some of the light is absorbed into the material. Metal surfaces are more reflective, so the angle doesn’t need to be so specific.

The settings to use when measuring the color of a gloss depend on the surface type. The standard measuring angles are:

• High gloss surfaces: 20°
• Mid gloss surfaces: 60°
• Low gloss surfaces: 85°
• International standard: 60°

It is important to know gloss measurements because gloss psychologically influences customers, so this aspect needs to be consistent across products and batches.

Color spaces are ways to organize colors into specific categories. A color space can be arbitrary, where colors recognizable in the physical world are assigned swatches and names, or have a mathematical organization plan. Color spaces are conceptual, and they help you understand the types of colors a device can produce.

What Are the Types of Color Spaces?

Think of a color space as encompassing any shade you can imagine based on the three primary colors — red, blue and green. Every color arising from any combination of these three falls within the color space. Typically, color spaces are developed on a diagram, which can be RGB or CMYK. How do you choose a color space? Dive into the definitions below to learn the basics.

Lab Color Space

One of the choices for measuring color is using lab color space. This space has the same components as others, though it is divided into lightness (L*) and two color components (a* stands for red and green value and b* stands for blue and yellow). The “lightness” is kept separate from the other parts because when you adjust it, the change more closely resembles human vision. In other words, if you use a lab color space and adjust the lightness, the outcome will look more “correct” to the human eye.

RGB Color Space

Red, blue and green are the primary colors, each of which is visible to the human eye. Visible colors are considered to be combinations of these three. To measure the possibilities of every color you can mix with red, blue and green, you can model an RGB color space, which is a three-dimensional plane in the shape of a cube with each color on an axis — a point’s position within the cube indicates its color makeup and saturation. The majority of digital images use an RGB color space.

There is some debate over RGB versus Lab color for reproducing images. In many cases, sticking with RGB will suffice, though projects requiring careful color correction and toning can benefit from the adjustment capabilities of Lab.

CMYK Color Space

The cyan, magenta, yellow and key (black) color space is another option, which is typically used in printed materials. When working with CMYK, you start with a white base and add the ink. The ink absorbs and reflects different light levels, giving you the desired colors.

From High gloss, to semi-gloss, to matte surfaces, the gloss level of any given material or object has a direct impact on the human visual perception of that material or object. Companies strive to achieve specific levels of gloss of their products for both functional reasons, and to improve the appearance of their products and help them stand out from the competition. It is, therefore, important that companies know how to measure gloss as proper guidelines will help companies consistently produce high-quality products.

Below, learn more about what gloss is, why it is important, and how it is measured. You may also want to know more about the kinds of industries that rely on gloss and how companies can meet gloss standards, which we will expand on.

What Is Gloss?

Gloss is the reflection of incident light from the surface of an object. The Reflection Law states that the incoming angle (the angle of incidence) is equal to the outgoing angle (the angle of reflection) denoted as Ɵi = Ɵr. For a wave that is incident on the boundary between two media, a reflection occurs.  

When surface imperfections at the boundary are small (compared to the wavelength of the incident light), the reflection is specular, and an image of the source is observed. An example would be the coatings used on automobiles, which are typically high-gloss and reflect a mirror image of their surroundings.

Diffuse Reflection is overwhelmingly more common and happens when the surface of the object is not smooth but rough or textured. Here, the light scatters in random directions. Diffuse reflection does not preserve an image of the source. A typical example is a low gloss or matte finish paint used on interior walls of houses and other buildings. 

Of course, it is also possible to have a mixed reflection (specular + diffuse), over which light is scattered in distribution about the specular.  Mixed reflections include semi-gloss samples, where an image of the source is observed but not well defined.

From a functional standpoint, controlling the gloss of manufactured products is critical for manufacturers to ensure batch-to-batch consistency, and to achieve the desired result for their products. Consumers do not want high-gloss mirror-like finishes on their interior walls, and they typically do not desire low-gloss low-sheen coatings on their automobiles (though this is a trend in some markets). 

And, since gloss levels directly impact consumer psychology and can make people give an object a second look, companies like to outfit their products with packaging and surfaces featuring specific gloss finishes to improve their visual appearance, potentially increasing sales.

Why Measure Gloss?

The first step in controlling gloss levels is being able to measure them. The gloss appearance of an object can be affected by several factors, such as the texture of the substrate, the smoothness of the material itself, and even film thickness of coatings applied to an object or surface. With all the factors that can affect gloss’s appearance, companies regularly measure gloss to ensure all their products have a consistent look. 

Not measuring gloss on a product can lead to several problems. For example, coatings manufacturers typically use gloss additives to achieve specific levels of gloss. Too much or too little can affect not only the coatings appearance when dried but also the coatings flow and leveling, curing times, adhesion, and long-term durability. Gloss levels also change the visual perception of the color of the surface or object. Coating a smooth surface and a textured surface with the same coating will result in the smooth-coated surface appearing much darker than the textured coated surface.

How to Measure Gloss?

Gloss is measured using a gloss meter, which functions by assigning a gloss unit (GU) to a measured surface. The gloss meter projects an incident light onto the surface. At an equal but opposite angle, the gloss meter measures the amount of reflected light. Typically, in industry, three angles are used to measure gloss, depending on the gloss level desired. High-gloss surfaces with a GU of 70 or above should be measured using a 20° gloss meter. Semi-gloss surfaces with a GU range of 10-70GU should be measured using a 60° gloss meter. Low-gloss surfaces having a GU below 10 should be measured using an 85°angle on a gloss meter.

What Is a Gloss Unit?

A GU is a measurement used for gloss. A standard GU measurement scale of gloss meters is determined by a reference black glass standard. This black glass is highly polished and features a defined refractive index that, when placed at a specific angle, has a 100GU specular reflectance. GUs are determined through this standard, as 100GU establishes an upper point calibration on a matte surface that can then be used to find how many GUs a product’s surface has. 

These 100GU gloss meters are appropriate for most non-metallic coatings and materials, such as plastics and paints. For more reflective materials, like mirrors or plated metal parts, companies use gloss meters with a higher upper calibration, regularly going up to 2,000GU.