The LD analysis measures matching peak size with OM at ∼1 µm, but under-reports the larger particle sizes. Interestingly, this under-reporting of the larger sizes by LD analysis is unique to the PET, recycled PET and PETG samples, as well as PVC (Supplementary Fig. ). The OM analysis of the recycled PET shows a size distribution with a similar character to the virgin PET, but with a broader range and, hence, greater average size (across all weightings). Morphologically, the SEM shows the particles to be visibly smoother than the virgin PET, but this is not reflected in the solidity measurements. The recycled PET sample displays a much broader range of solidity, with many tortuous, frayed particles in the <10 µm region. PETG is a copolymer of PET and poly(ethylene glycol) which prevents crystallization of the plastic. This results in a lower modulus which can explain why the PETG has more frayed, lower solidity particles. The size is slightly larger, but with similar bimodality -peaks at 1 µm and 10 µm. There is, however, a significantly smaller proportion of the smaller 1 µm particles compared to the PET sample. The size distribution obtained by LD analysis under-reports both the largest and smallest particles, which is potentially due to the large number of particles across a very broad range, with no discernible peak above 4 µm. The position of the peak is approximately matching the OM-obtained distribution (∼ 2µm from LD versus 1 µm -3 µm for OM).