What is Blackness

Blackness is usually used to describe the depth of color, that is, the degree of "darkness" of the color . In layman's terms , it describes how dark black is . It refers to the ability of an object to absorb visible light. The higher the blackness, the more light the object absorbs and the more light it reflects. The less light that passes through a material, the darker it appears. This property is particularly important in pigments such as carbon black, as the degree of blackness affects the visual effect of the material and the performance of color applications.

Especially in applications such as pigments, inks, coatings, plastics , and textiles, blackness measurement is key to ensuring product quality and consistency .

It should be pointed out that in the blackness measurement, the blackness performance of carbon black is closely related to its dispersion performance . Therefore, when preparing the blackness measurement sample, it is necessary to ensure that the pigment can be evenly dispersed in the substrate. If necessary, a dispersant can be added to avoid the influence of particle aggregation on the blackness . In addition, before using a spectrophotometer to measure the blackness index, it must be calibrated, and the calibration curve of the instrument cannot be used directly.

Common reference standards and measurement methods for blackness

1. DIN 55979 - Determination of the Black Value of Carbon Black Pigments

· Scope of application : Mainly used for carbon black pigments and carbon black products, suitable for coatings, inks, plastics and other industries.

· Measurement method : The blackness index (My value) is measured by spectrophotometry, and the blackness value is calculated by the formula. The My value is calculated based on the reflectivity of the sample at a specific wavelength.

· Application : Widely used to evaluate the jetness of carbon black pigments to ensure that the product has a consistent black appearance.

2. ASTM D3265 - Standard Test Method for Carbon Black — Tint Strength by Reflectance Method

· Standard name : ASTM D3265

· Purpose : This standard is used to measure the tinting strength of carbon black in plastics, inks and coatings, that is, the blackness effect produced when carbon black is mixed with a white substrate (such as titanium dioxide).

· Scope of application : Applicable to the evaluation of carbon black pigments, especially for judging their dyeing ability in different formulations.

· Measurement method : Mix carbon black and white substrate in a certain ratio, and then measure its reflectivity to evaluate its tinting ability (Tint Strength). The higher the tinting strength, the darker the carbon black is in the white substrate.

3. ISO 18314-3 - Colorimetry: Measurement of Jetness and Undertone of Black Pigments

· Standard name : ISO 18314-3

· Scope of application : Suitable for measuring the blackness and hue deviation of various black pigments, especially carbon black pigments.

· Measurement method : Use a colorimeter or spectrophotometer to measure the reflectance of the sample and calculate the jet value and hue deviation.

· Blackness parameters :

o My (blackness value): Indicates the blackness of the color. The higher the value, the darker the blackness.

o Mc (dark black value): considers the influence of hue on black and reflects the visual effect of black.

o ΔM : Used to quantify the blue or red deviation of black, ΔM > 0 is blue, ΔM < 0 is red.

· Application : Mainly used for products with high blackness requirements to ensure the deep blackness and visual consistency of the pigment.

4. Blackness parameter calculation formula :

Combining several commonly used standards, the following is the parameter calculation formula for evaluating the blackness index:

1. My (blackness value): This formula is used to calculate the darkness of a black sample . The higher the value, the darker the blackness. The calculation of the blackness value My is based on the brightness component Y in the tristimulus value and the 10° observer angle :

My = 100 * log (100 / Y)

Y: The Y value of the sample, that is, the brightness component of the sample's tristimulus value. Usually indicates the brightness or reflectivity of the sample under standard observation conditions.

My determines only the lightness of the sample and does not take into account the color background. Since the black background affects the visual assessment, the hue-dependent blackness calculation must also be considered .

2. Mc (Black Value): Reflects the depth of black, taking into account the hue shift of carbon black (such as bluish or brownish).

Mc = 100*(log(Xn / X)–log(Zn / Z)+log(Yn / Y))

X , Y , Z : The tristimulus values of the sample (the tristimulus values in the CIE 1931 colorimetric system), representing the red, green, brightness, and yellow and blue components of the sample, respectively.

Xn , Yn , Zn : The tristimulus values of standard white (usually standard white under D65 light source), used for comparison and correction of color deviation of samples.

If the background color is bluish, the black value Mc represents a higher blackness; if the hue is brownish, the black value Mc represents a lower blackness. The difference between the black value Mc and the black value My defines the hue of black, the so-called background color (dM):

3. dM (Hue Deviation): Indicates the hue difference between the black values Mc and My . The background color dM describes the amount of blue hue when it is positive , and the amount of brown hue when it is negative.

dM = Mc – My = 100*(log(Xn / X)–log(Zn / Z)

·  dM > 0 indicates a bluish tint.

·  dM < 0 indicates a brownish tint.

4. Tint Strength

T( Tint Strength ) =(S / I)×100

·  T : Carbon black tinting strength, expressed as a percentage.

· S : The reflectance reading of the sample, that is, the measured reflectance value of the carbon black sample.

·  I : Reflectance reading of a reference carbon black, usually an ASTM standard reference sample.

3nh blackness measurement solution

3nh benchtop spectrophotometer TS85 series can provide you with blackness measurement , for example, 3nh TS8560 is a high-precision benchtop spectrophotometer designed to meet the strict requirements of various industries for color measurement. The instrument adopts the core spectrophotometric technology independently developed, equipped with a dual-array CMOS image sensor, with high sensitivity and wide spectral response range, to ensure the accuracy and stability of the measurement results. It can accurately measure the carbon (My, dM) value and Tint Strength of the sample .