The science of surface: Quality control is redefining the ink and coating industry

The halls of the Bombay Exhibition Centre remained clear of the solvent odours historically associated with the coatings industry. This shift aligns with an industry move toward sustainable formulations. With over 1,000 brands and 75 countries represented, the event served as a technical forum for surface science, emphasising the data provided by analytical instrumentation in print and packaging.

The five-pillar strategy of ink integrity

Pradeep Mahajan, partner at Viba Scientific Instruments, stated that modern ink manufacturing requires a minimum of five core instruments to ensure market standards. While the viscometer is used for fluids and pastes ranging from one cps to six-million cps, analytical tools are increasingly used for specific technical issues.

Mahajan cited moisture content in ink as a variable that affects adhesion and drying times. By using a Karl Fischer titrator, manufacturers can detect purity and moisture levels. Mahajan noted that his team analyses the specific application before recommending a viscometer, as different manufacturing challenges require specific technical configurations.

Testing challenges in recycled materials

The industry shift toward sustainability has increased the testing requirements for recycled materials. Jayesh Darji, manager of technical services at Venture Instrumentation Technologies, explained the physics involved in testing recycled PET (rPET). Unlike virgin polymers, recycled materials contain contaminants that vary by batch, affecting viscosity.

Darji described a testing process where rigid PET is dissolved at 180°C in solvents such as phenol or methanol. The solution is stirred for several hours to maintain consistency. If the PET is not fully dissolved, it can obstruct the capillaries of the testing equipment. A single sample takes approximately 45 minutes to process to determine if the material meets automotive or apparel standards.

Ultrasonic monitoring of coating layers

At the Komal Scientific International booth, technical manager Kovendhan S demonstrated the DeFelsko Positector 200/6000. As multi-layer coatings become standard for food and pharmaceutical barriers, the ability to measure individual layers has become necessary. While traditional testing uses the Eddy current principle for metal substrates, ultrasonic technology is used for non-metal substrates like wood and plastic films.

The equipment measures thicknesses from one-micron to 1500-microns, distinguishing between a primer, a base coat, and a glossy finish in a single measurement. Kovendhan also noted that spectrophotometers monitor colour fading to ensure Delta E values remain within 0.7 over one year, providing data on how labels perform under warehouse lighting or shipping conditions.

Surface energy and adhesion physics

Brajesh Kumar, zonal manager-sales at Agaram Industries, discussed the role of surface free energy in ink adhesion. While dyne pens are used for quick checks on BOPP or PET films, high-stakes applications require more precise measurement of wetting phenomena.

Kumar explained that the surface tension of the ink must be lower than the surface free energy of the substrate to achieve wetting. If the ink tension is higher, the liquid will bead, resulting in poor print quality and low scratch resistance. This science is also applied in the solar industry, where super-hydrophobic coatings repel dust. Technicians use portable contact angle meters to test panels in the field. By measuring a water droplet on the glass, the meter calculates the contact angle; a significant change in this angle over six months indicates coating depletion.

Analytical standards in the Indian market

PaintIndia 2026 signaled a transition in the Indian market from basic quality control (QC) to analytical quality control (AQC). Small and medium enterprises are adopting high-performance liquid chromatography (HPLC) to verify 99.9% solvent purity and high-speed dispersers operating at 12,000 RPM to create homogeneous mixtures.

This analytical shift is influenced by waste reduction requirements. Kovendhan noted that measuring a coating while wet can prevent the over-application of material. Detecting an excess of a few microns early in the production cycle reduces raw material and energy consumption.

The absence of solvent odours at the event reflects a move toward data-driven manufacturing. For the packaging industry, the quality of the final print is increasingly determined by laboratory analysis and precise instrumentation.