To characterize the MP powders quantitatively, the samples were analyzed using a multiscale optical microscopy (OM) method using two magnifications. Wide-field (∼ 4.5 mm × 4.5 mm) images using stitching and tiling with a 10× objective were used to measure a statistically significant amount of MPs. A 40× objective was used to get higher resolution images of the smallest MPs. The data were combined into a single size (equivalent diameter) distribution to be compared with the LD measurement. OM is a useful technique for size characterization as a wide range of microscopes, from cheap and simple to sophisticated high-resolution devices, are available. The shape of the particles can be quantified using shape factors such as the aspect ratio (AR) and solidity.