Application of Colorimeter in Measuring Whiteness of White Silk

In the color world around people, white is the most encountered, and people often use whiteness to describe the "degree of whiteness", but so far, there is no exact definition of the concept of whiteness. White, like other colors, is one of the sensations that the reflected light enters the human eye after the object is irradiated, acts on the visual organs and is reflected by the brain. In the chromaticity color space, the wavelength of white is in the range of 470nm to 570nm. And constitute a three-dimensional space color. Whiteness is a measure of "whiteness", and white itself has the color properties of high reflectance and low purity. Whiteness can be roughly divided into non-whitening and fluorescent whitening. It is not necessary to consider the fluorescent effect of the sample without whitening, but the sample with fluorescent whitening, under the light irradiation, not only has reflected light, but also has the fluorescence produced by the fluorescent agent itself, so the fluorescent factor of the fabric itself should be considered.

Most of the refined white silks for export are raw white products without fluorescent whitening treatment, and the research object of this paper is this kind of products, without considering the fluorescence factor.

Analysis on the Current Situation of Measuring Method of Whiteness of Refined White Silk

Whiteness is not only an important physical quantity to measure the quality of refined and processed products, but also an important assessment item determination of this value can not only provide measured data for product quality control , but also can be used to adjust and control the actual whiteness. Process parameters such as silk degumming rate have positive significance for product quality control and improvement. From the analysis of the current whiteness inspection status of production enterprises and the control of the whiteness of refined white silk by the Commodity Inspection Bureau , the methods for measuring the whiteness of refined white silk are mainly divided into two categories.

1. Visual inspection evaluation method

This method, also known as the direct comparison method, is a traditional method. It has the advantages of convenience, simplicity, and intuition, but the disadvantage is that it is easily affected by light sources and lighting conditions, has no quantitative concept, and is often subjective.

2. Whiteness meter measurement method

This method is also known as a physical (objective) evaluation method, expressed by reflectivity R, and its characteristics are measured by instruments, with a quantitative concept, and subjective factors are excluded, but the value of R is related to the type of instrument, performance, sample placement angle, etc.

Confirmation of Measuring Principle of Whiteness of Refined White Silk

Whiteness inspection and textile color difference inspection belong to the category of color measurement. Color measurement is a testing technology that applies the theory of colorimetry. Colorimetry is a new marginal subject developed in recent decades, and it is relatively mature in theory and application. When it comes to color measurement, various color measuring instruments are inseparable. The Whiteness Meter mentioned above also belongs to its category.

With the development and perfection of the theory of colorimetry, numerous whiteness calculation formulas and representation methods have emerged. Since the test object is refined white silk without whitening treatment, it is determined to choose the HON TER SERIES. This system is established by comparing Xinxin white with the sample in the uniform color space. Instrumental control of whiteness is commonly used. Obtain L, a, b, and calculate according to the following formula:

W white = 100- [ (100- L) ² a ² +b ² ] ^1/2

Field test of smelting white silk

1. Samples: According to the distribution of varieties of refined white silk for export, several common varieties of more than a dozen specifications were selected as representative test objects.

2. Test instruments: Japanese Colorimeter and domestic Whiteness Meter.