Using Gas Pycnometry to Determine the Density of Paint

Paint manufacturers who use density analysis for quality control and formulation consistency have expressed an interest in gas pycnometry to save time and achieve accurate results.

The traditional method ASTM D1475 Density of Liquid Coatings, Inks, and Related Products has been an industry standard for a few decades and uses a “weight-per-gallon (WPG)” cup as a container to measure the density of the paint. ASTM D1475 uses distilled water as a calibration medium and uses SI units such as grams per liter or pounds per gallon to express the density of the paint. Even though ASTM D1475 is an accepted, conventional method to measure density of paints, it is a technician-dependent and time-consuming process. The technique requires multiple steps such as centrifuging the sample, scraping the paint off, and cleaning the steel cup containing the paint to ensure no residue is left behind before the weighing.

Gas pycnometers, including Ultrapyc instruments, combine Archimedes’ principle and Boyle’s gas law to accurately measure volume and density. For this report, gas pycnometry is investigated as an alternative methodology to WPG by demonstrating ease of use, data accuracy and time-saving capability.

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