Soap bars (based on sodium salts of fatty acids) and syndet bars (using added sodium salts of isethionate esters) suffer from the presence of grit like spherical particles. These hard particles cause extensive manufacturing problems (such as difficulty in melting the pre-bar blends) and are disliked by the consumer. Grit is formed in the initial crystallisation/precipitation of the soap ingredient and various ingredients are subsequently blended and melted before pressing out into bars. The presence of grit affects all the downstream processing stages - these hard lumps cause equipment erosion and slow down the melting process, block filters and so on. Grit also abrades skin when washing and has an unpleasant feel. This has assisted the uptake of liquid soaps and body washes in the West. However, the use of liquid soaps has increased the need for packaging and the emission of more greenhouse gases due to transporting what is effectively water. Innospec is the only Western major player doing research in this area and cannot make the next step in utilising new improved ingredients which will result in a change in consumer preference. A successful outcome would result in Innospec (with its research base in the UK) becoming the largest European supplier of key ingredients for a rejuvenated soap bar market. A multi-disciplinary approach utilising the CDT in Complex Particulate Products and Processes is required to fully characterise these grit particles for the first time and to identify routes for their prevention or elimination. This project builds on the research of Cohort 1 CDT student Mohammed Jeraal. Reference: Process-Focused Synthesis, Crystallization, and Physicochemical Characterization of Sodium Lauroyl Isethionate - https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.7b04237 Aims: To define the crystallisation processing boundaries that form grit in soap bars and to develop counter measures to reduce or eliminate grit. Objectives: Develop measurement/analytical methods to determine the effect of the current manufacturing process that leads to the formation of grit. Examine the dynamics of the melt crystallization in-situ as a function of rheological behaviour and crystallization supersaturation. Study the influence of the ingredient composition and impurities on the crystallisation process specifically addressing how this impacts upon the resultant melt viscosity and particle aggregation in solution. Understand and characterise ingredient and product crystallisation kinetics and its inter-relationship with particle morphology (crystal form) and develop a process model for the manufacturing process. Develop an understanding of what factors affect the crystal form, grit formation and its elimination - this will cover assessing the current synthesis conditions, the effect of impurities, chemical additives and the potential to change the fundamental chemistry by the use of other ingredients.