The Gardner Scale allows for standardized color measurement of yellow to brown transparent liquids and is instrumental in a range of industries. Image Source: Unsplash user Sonja Langford
In some transparent liquids, colorlessness is king and manufacturers rely on the APHA/Pt-Co/Hazen color scale to ensure both chemical purity and aesthetic appeal of colorless and near colorless liquids. Other transparent liquids, however, have different color properties, either by nature or by design, that require a separate, specialized color measurement scale for yellowness beyond that offered by the APHA. Yellow to brown transparent chemicals, liquid pharmaceuticals, food products, and beverages are ideally suited for Gardner Scale measurement.
The Gardner Scale and Color Consistency
The Gardner Scale was developed in the 1920s to classify the color of drying oils, varnishes, fatty acids, polymerized fatty acids, and resin solutions. The scale originally consisted of 18 liquid standards composed of potassium dichromate, ferric chloride, cobaltous chloride, and potassium chloroplatinate and represented in sealed glass tubes for visual comparison, ranging from light yellow (1) to dark brown (18). These liquids were vulnerable to instability, color variation, and reproduction difficulties, and were eventually replaced by glass filters in 1958 in an attempt to enhance precision. However, the Gardner Scale remained a visual evaluation method relying on the subjective human gaze, leading to inaccuracies and difficulties maintaining color consistency.
Monitoring the color of linseed oil allows manufacturers to produce the precise consistency consumers are seeking. Image Source: Flickr user Alsatian
