Turquoise green glaze , also known as “autumn okra green glaze,” is a porcelain glaze color. It’s a new type of green glaze created during the Yongzheng period of the Qing Dynasty. Different observers will interpret the color of turquoise green porcelain differently. To control the appearance quality of turquoise green porcelain, a spectrophotometer can be used to measure it.
What does the turquoise porcelain color represent?
Turquoise is a very mysterious blue, with RGB of R:51, G:161, and B:201.
Turquoise’s exact value is almost undetermined. It’s an ambiguous color, interpreted differently by different people, representing the concept of “hidden.” In the printing industry, this color can be highly distorted. In the spiritual realm, it’s a color of the unattainable divine realm, a unique color alongside gold and silver.
Turquoise is also a porcelain glaze color. The modern formula is made of barium sulfate, calcium carbonate, boric acid, etc. Its color is light yellow with a slight green hue, similar to the color of turquoise, hence the name “turquoise”.
Green Similar to turquoise, lake blue is colder, while turquoise is warmer and slightly brighter. To mix turquoise, you can add a little white and a trace amount of lemon yellow to lake blue.
However, in the actual coloring process, different observers have difficulty determining the color of turquoise, so the resulting turquoise color is often suboptimal. Furthermore, if there are differences in colorants and firing processes, turquoise porcelain products will also have color differences. To control the color quality of porcelain, a spectrophotometer can be used for testing.
Spectrophotometer evaluates the color quality of turquoise green porcelain:
When visually observing color, the color assessment results of turquoise green porcelain can easily deviate due to factors such as lighting source, viewing conditions, and subjective factors. As people’s expectations for the color of porcelain products become increasingly stringent, a precise color measurement technology that can complement the human eye’s color perception is needed to control the appearance and color quality of porcelain.
The color of matter is perceived by the human eye, resulting from the brain’s ability to discern the different properties of light that strike the retina. The spectrum forms the basis of color. The color emitted by a light source is called illuminant color, while the color of an object we observe is called object color. Object color is determined by the object’s nature, specifically its internal structure. Matter exhibits a variety of colors because, under the influence of energy from a light source, electrons within its constituent particles undergo transitions, selectively absorbing or emitting specific wavelengths of light, thereby displaying its characteristic color.
A spectrophotometer is a photoelectric integrating colorimeter that uses an internal standard light source to measure transmitted or reflected color. The color of an object is generally expressed using three scales: hue, chromaticity, and lightness. Hue represents the characteristics of colors such as red, green, yellow, blue, and purple. Chromaticity uses the visual perception of equal brightness without color points to express the intensity of the color on the surface of an object and assigns a scale. Lightness indicates the relative lightness or darkness of an object’s surface. It is a scale based on the visual perception of the surface under the same lighting conditions, using a whiteboard as a reference.
When users use a spectrophotometer to test the color of turquoise porcelain, they can accurately assess the color deviation between the sample and the standard through the measured numerical results, thereby avoiding deviations caused by subjective factors in the human visual evaluation process and better controlling the color quality of turquoise porcelain.
Color Measurement of Turquoise Green Porcelain
Core Measurement Steps
- Sample Preparation: Clean the turquoise green porcelain surface to remove dust, fingerprints, or residual stains. For porcelains with glazed or textured surfaces, mark the flat, uniform area as the measurement point to avoid interference from uneven textures.
- Device Selection: Use a spectrophotometer(preferably with d/8° measurement geometry) instead of a colorimeter. This type of device accurately captures the subtle color variations of porcelain glazes, especially the unique “turquoise green” tone that combines blue and green hues.
- Device Calibration: Calibrate the spectrophotometer with a standard white tile according to the manufacturer’s instructions. Ensure the calibration environment is free of strong ambient light (e.g., direct sunlight) to maintain measurement accuracy.
- Measurement Execution: Place the device’s measuring port tightly against the marked area of the porcelain. Take 3–5 repeated measurements at the same point and calculate the average value, which helps reduce errors caused by glaze thickness differences.
- Data Analysis: Convert the measured data into the CIELAB color space(the most widely used standard for ceramic color measurement) to quantify key parameters:
- L*: Represents the lightness of the turquoise green (higher values mean a brighter glaze).
- a*: Indicates red-green tendency (negative values reflect the green tone in turquoise green; the more negative, the stronger the green).
- b*: Reflects yellow-blue tendency (negative values correspond to the blue tone in turquoise green; the more negative, the stronger the blue).
Key Notes for Porcelain-Specific Scenarios
- Glaze Translucency Impact: Turquoise green porcelain often has semi-translucent glazes. Select a spectrophotometer with a translucency compensation functionto avoid color distortion caused by light penetration through the glaze.
- Batch Consistency Control: When measuring multiple porcelains in the same batch, use the first qualified sample as the “standard color” and calculate the color difference (ΔE) with other samples. Generally, ΔE ≤ 1.0 indicates consistent color, meeting industrial quality requirements.
