Gardner Color Liquids | Color Measurement

Color measurement is particularly important in the quality assessment of colored liquids in the chemical, resin, varnish, or coatings industries. While monitoring Color Control Of Liquid Chemical With Gardner Color, experts in the field draw upon the Gardner color or the APHA/Pt‑Co/Hazen (Hazen/Pt‑Co) colorimetric scales, which are most suited for transparent or translucent liquids. In this article, I will examine Gardner Color: A Color Scale for Translucent Liquids, relative both to APHA’s scales as well as to contemporary methods beyond Visual Comparison to Liquid Standards for Gardner Color With Instruments.

What is the Gardner test method?

Gardner test method, more widely known as Gardner Color method, is based on a systematic approach designed for measuring the color of transparent or translucent liquids. It relies on visual comparison of the test sample against a maximum of 18 sequential standard Gardner color scale glass filters. The method results in a color number Gardner scale value ranging from 1 for light yellow to 18 for dark red-brown, and 0 for distilled water.

What color is Gardner?

In simple terms Gardner 1 refers to a pale yellow color, as the number increases the color transitions to a deeper shade, moving from yellow to amber, and eventually reddish brown. Gardner 18 labeled the sample as highly saturated dark yellow. This scale ranges from 1 to 18 and helps to assess the purity and stability of liquid chemicals, oils and resins.

How to measure Gardner Color?

There are generally two approaches that one can take to assess Gardner color.

● Visual Comparison: A sample is juxtaposed next to the Gardner color standard under regulated light conditions. The evaluator makes comparisons to assign the most suitable Gardner value. This method is popular because of its use and is common in routine checks.

● Instrumental Measurement: A colorimeter or a spectrophotometer can assess the light transmission through the liquid sample and thus evaluate the Gardner color as capture measurement. This method is Gardner color measurement is not subjective to the human vision therefore is accurate and repeatable.

Gardner Colour Scale & Standard

The gardner colour scale was developed with the purpose of matching varying intensities of color seen in transparent liquids, particularly those with yellow to brownish hues. The standard scale is from 1 to 18. However, most industrial samples fall between Gardner 1 to Gardner 8. The Gardner standard is essential for color management as it helps maintain consistency during the color management of transparent liquids across different production batches or plants.

APHA/Pt‑Co/Hazen compared to Gardner color scales

APHA color scale also know as Pt‑Co or Hazen scale is one of the systems designed for color evaluating liquids. However, it is meant for very light or almost colorless liquids. It is measured on a scale of 0 to 500 APHA units with 0 being water white clear.

The crossover between the APHA and Gardner color scales is said to occur around APHA 300-500 and Gardner 1-2. That is, when a liquid becomes too dark for accurate APHA assessment, analysts switch to the Gardner scale. Together, these systems allow the assessment of the full spectrum of liquid color, from clear and colorless to dark amber.

Color Management of Transparent Liquids

Color Management of Transparent Liquids encompasses these essential color management practices:

● Setting color standard thresholds with Gardner or APHA.

● Routine measurement of product samples are conducted for accuracy, conformity, and compliance with standards.

● Utilizing proper measurement tools or comparison techniques.

● Controlling uniformity across processes and consistency with raw materials.

● Knowing and selecting the appropriate range for the color value determines the value for the colors.

Petrochemical, paints and coatings, plastics, and food processing industries utilize both APHA and Gardner systems for color accuracy and consumer satisfaction.

There is a certain relationship between Gardner color and platinum-cobalt color, and they can be converted using the following formula: 

 Pt-Co （Platinum-cobalt） color = 13.26 × Gardner color - 7.58 

 Gardner color = 0.075 × Pt-Co（platinum-cobalt） color + 0.564

The Liquid YS6060 Spectrophotometer is designed by 3NH specifically for customers who need to measure the color of transparent products. It can measure the color of liquids at room temperature or high temperatures, such as methanol, sodium methoxide, ethylene glycol, bisphenol A, electrolyte, various oils' Lab color, Pt-Co platinum-cobalt color APHA, Hazen blackening index, Gardner Gardner color, Saybolt Saybolt color, ASTM D1500, acid washing color, ADMI, LovR, LovY LovR color, etc. It is commonly used in quality control and color management fields to ensure color consistency in product production. 

Below are some features and functions of the 3NHYS6060 colorimeter: 

 1. Color measurement: The YS6060 colorimeter can measure color parameters of samples, such as L*a*b*, L*C*h, XYZ, etc., to describe color brightness, chroma, and hue. 

 2. Multiple light sources and viewing angles: It supports various light sources and viewing angles to accommodate different sample types and applications. 

 3. Data recording and analysis: Measurement data can be saved and analyzed to track color changes and perform quality control. 

 4. Software support: The YS6060 colorimeter typically comes with dedicated software for managing and analyzing color data. 

 5. Optional accessories: Depending on specific requirements, different accessories such as sample holders or sample chambers can be added to accommodate various sample types. For high-temperature products, heat-resistant colorimetry tubes can be used in conjunction with a heating device.

Visual comparison to liquid standards for Gardner color

Many industries utilize color measurement with Gardner’s method for the color control of liquid chemicals due to its efficiency and cost effectiveness. The method involves placing the liquid samples into clear test cells and comparing them with the Gardner color standards. The closest visual matching color is selected as the result.

Visual comparison to liquid Gardner standards is very useful for initial tests and smaller businesses that require immediate results. The method is fast, however results can vary because of the lighting, the observer’s skill, and tired eyesight.

Instrument vs Visual: Pros and Cons

Visual comparison is simple and inexpensive compared to instrumental approaches. However, both lack intricacies and are subject to human factors. Instrumental accuracy improves reliability, however incurs initial cost and maintenance expenses.

 Laboratories today lean heavily on instrumental analysis for accuracy. Nonetheless, all methods of assessment hold their grounds and importance.

What is the color number Gardner scale?

The color number Gardner scale is a system for assessing the degree of resemblance a sample has to one of the standard colors, particularly within the Gardner color scale. Gardner color scale 0 is reserved for water-clear liquids. Gardner color scale 1 to 18 signify a continuum of increasing intensity and darker shades, which is often observed in aged or contaminated liquids.

 What is the color of the Gardner scale chart?

 The chart of the Gardner scales shows colors together with values ranging from  light yellow  to a deep reddish brown, ordered from 1 to 18. This chart is used during training and also serves as a reference during visual assessments. Many comparator tools incorporate the chart with glass filters of the corresponding values.

What is the Gardner Color method?

The Gardner Color method encompasses the particular techniques used to gauge a liquid’s color based on the Gardner scale. Color measurement on Gardner scale involves both visual and instrumental methods—they must adhere to a sample prep, lighting, and measurement conditions framework. The method is designed to promote meaningful color assessments regardless of the users or location.

APHA color chart / APHA colour / APHA color scale

The APHA color scale (Hazen or Pt‑Co) are also used for water, various solvents, and other chemicals, where even faint traces of color may signify possible contamination. The APHA color chart is based on clearly defined standards for and encompasses values ranging from 0 to 500, where the values indicate increasing concentration of yellow tint within the substance.

The APHA scale is better for observing clear or colorless liquids, and, therefore, for monitoring water quality, alcohols, and other transparent liquids as opposed to the Gardner scale, which is better for darker or more saturated colors.

Best Practices for Color Control

Best practices for effective Control Of Liquid Chemical With Gardner Color include:

● Selecting the proper scale for the anticipated color range of the the product.

● Conducting frequent instrument calibrations for maintained reliability.

● Cross-validation trained employed visual and instrumental invaldiated techniques.

● Standardized sample and lighting conditions to eliminate variability.

Long-term trend analysis and quality assurance through logging and tracking for documented results.

Applications and Industries

The Gardner color scale finds applications in:

● Varnishes, resins, and oils

● Petrochemical products

● Plastics and additives

● Coating and ink formulations

● Industrial solvents

The APHA scale, in comparison, is important for:

● Water treatment and monitoring

● Alcohols and solvents

● Pharmaceuticals

● Food additives and clear beverages

Summary

The Gardner color scale effectively evaluates the quality of translucent liquids ranging from yellow to amber. This assists manufacturers in maintaining color benchmarks, detecting any changes that might impede performance. We may rely on the Gardner color scale along with APHA/Pt-Co/Hazen scales for evaluating lightly and intensely colored liquids, respectively.

Color Management involves work with transparent liquids and requires understanding the Gardner Color method, knowing how to measure it, and determining when using APHA is more appropriate. Either through visual comparison for Gardner color or accurate measurements using instruments, maintaining consistent standards is critical to selection and ensures reliable, consistent product quality.

Click here for more information

Gardner liquid Spectrophotometer TS4020