Understanding Hydroxypropyl Starch Phosphate Usage

Thank you for sharing your detailed experiments with Hydroxypropyl Starch Phosphate (CreamThick™). Your observations about the different textures achieved at varying concentrations (4-10%) are valuable and consistent with how thickeners behave – higher concentrations generally result in higher viscosity and a more gel-like or paste-like texture.

Regarding your questions:

• Can you use it above the recommended rate (0.5-5%)? The recommended usage rate of 0.5-5% provided on the website is a general guideline to achieve typical thickening effects. The product description also notes that when used as the sole thickener, a rate of at least 4% is recommended. While you have successfully achieved desired textures at higher rates (7-10%), it's important to understand that using ingredients above the manufacturer's recommended range may affect the overall stability of the formulation over time. The texture might be thicker initially, but you should conduct stability testing (e.g., observing changes in viscosity, appearance, separation over time and under different temperature conditions) to ensure the formulation remains stable and performs as expected at these higher concentrations.

• Is the dissolution behavior normal (small spherical particles)? Yes, the observation of small particles that disappear upon application is likely normal, especially when mixing manually with a whisk and spoon. Hydroxypropyl Starch Phosphate is a powder that needs to be properly dispersed and hydrated in water to form a smooth gel. Manual mixing might not provide enough shear to fully break up all powder aggregates, resulting in small, undissolved or partially hydrated particles (which you described as "flakes" or "small glass-like spheres"). These particles then fully hydrate and disappear when spread on the skin due to the moisture and shear from application. Using a higher-shear mixer (like a homogenizer or even a stronger lab mixer) would typically result in a smoother, more uniform gel without visible particles.

In summary, your experiments show the versatility of CreamThick™ in creating different textures. While you can experiment with higher concentrations to achieve a thicker gel, always perform stability tests on your final formulation. The presence of small particles with manual mixing is common and indicates the need for thorough dispersion, which happens upon application to the skin.

Relevant Product: CreamThick™ (Hydroxypropyl Starch Phosphate)