Regarding your questions for college project use

1. Permission to use information for college project

Yes, you are welcome to use the knowledge and articles from the Myskinrecipes website, forum, and contributions from the team, C7, and members for your college science project on DIY cosmetics, as long as it is for non-commercial use. C7 has kindly granted permission and encourages the sharing of knowledge in cosmetic formulation.

2. Direct application of fragrance oil (Warm Vanilla Sugar)

Applying fragrance oil directly to the skin at 100% concentration, even in small amounts, is not recommended for two main reasons:

• Risk of Sensitization: Fragrance oils contain compounds known as sensitizers (e.g., coumarin found in vanilla scents). Regulatory bodies like the EU have limits on the concentration of these substances in finished products (e.g., coumarin limit is 2%). Fragrance oils are formulated assuming they will be diluted significantly (typically 5-30% depending on the application). Applying the pure oil at 100% will exceed these safe concentration limits, greatly increasing the risk of causing skin irritation or allergic reactions.
• Suboptimal Performance: Fragrances require a suitable base (like alcohol or oil blends) to control their evaporation rate and longevity on the skin. Applying the pure oil might not provide the desired diffusion or lasting scent compared to a properly formulated perfume or body product.

3. Using Pro Polymer for thickening surfactants/face wash

While it is technically possible to use Pro Polymer (Acrylate Crosspolymer) to thicken surfactant-based products like face wash gels, it is not the most suitable thickener for this application.
Many surfactants can be thickened more effectively and easily by other types of thickeners. For non-ionic surfactants, which are common in gentle face washes, alternatives like SugarThick (PEG-120 Methyl Glucose Dioleate) or Xanthan Gum are generally preferred.
Using Pro Polymer in surfactant systems can often lead to excessive foaming during mixing, making it difficult to achieve the desired consistency smoothly. SugarThick, for instance, is much easier to incorporate and thickens readily without generating excessive foam.

4. Matt Silica causing pilling and white cast

Based on the information provided, Matt Silica itself is unlikely to cause pilling or a significant white cast at a 5% concentration. Matt Silica is a powder designed to absorb oil and provide a matte finish, not to provide coverage or whiteness like pigments (e.g., titanium dioxide).
The pilling you experienced is more likely caused by silicones, potentially from the Silky Serum Base Plus in the Vitamin C Repair Serum you applied before the sunscreen. Silicones from different products can sometimes interact and cause pilling when layered.
Regarding the slight white cast, while 5% silica wouldn't typically cause this, it's possible that the Vitamin C in the serum you are using is effectively lightening your skin over time, which might contribute to a perceived "whiteness" when applying other products.