Tinting strength control method for eliminating adjustments in effect colours

 
Consistency between batches of effect pigment paints, such as metallics and pearlescents, represents one of the biggest challenges for manufacturers in the sector. The complexity of ensuring color consistency between different batches implies extensive quality control processes, which often significantly increase production lead times. Rigorous standardization of all stages of the process, from the weighing of ingredients to the final application, is key to minimizing variations between batches. A critical aspect of this control is the tinting strength of the metallic and pearlized bases, which must be strictly monitored. This tinting strength is crucial if the bases are to provide the expected color and visual effect when mixed with other ingredients. Sensitive and precise control of the tinting strength can reduce or even eliminate the need for additional adjustments to the final color, increasing the assertiveness of the product. The conventional method of controlling tinting strength is characterized by several manual steps, such as weighing samples, mixing with a standard base, applying to panels and drying in an oven. This process is not only time-consuming but also susceptible to human error, and often relies on visual assessment, given the complexity of the effect pigments. Although reflectance measurement with a multi-angle spectrophotometer is used, it is not always sufficient to capture all the nuances of effect pigments. In this study, a new technology was evaluated to measure and control the wet tinting strength of effect pigment bases using light transmission spectroscopy. This method is already used to assess the tinting capacity of opaque and transparent pigments and is now being tested for metallic and pearlescent pigments. The initial phase of the study focused on ensuring that the measurements made with the new technology were reproducible and consistent over time, using the same sample. Once the stability of the measurements was guaranteed, a sample at the upper limit of the specification and another at the lower limit according to the reflection method were used for color formulation. Another two samples, now controlled at the upper and lower limits using the proposed method, were also used to formulate the same colors at the same concentration. The impact on the ?E conventional reflection when controlling the tinting force using the two methods was evaluated. The results showed that the use of the new technology enabled greater color reproducibility in paints produced from bases controlled by the new tinting strength method compared to paints produced with bases controlled by the conventional method. The high sensitivity of transmission spectroscopy for controlling tinting strength made it possible to narrow the approval limits, which contributes to reducing costs by optimizing the use of resources and minimizing rework due to quality deviations. The use of this new technology could bring significant advances in quality control in the paint industry, allowing for future in-line automation of quality control, since the analysis is carried out wet, enabling a significant reduction in analysis time. In addition, the method promotes more sustainable practices, in line with the demands for ecologically responsible industrial processes.