Base Powder Analysis for Oily, Yellowish-White Skin

You're looking for a beige, waterproof, oil-controlling loose powder that prevents dullness, provides a radiant but non-shimmery finish, and offers low-medium coverage. Your base formula includes Allantoin, MatteSilica™, and Beige Iron Oxides EasyMix™. The choice of the base powder is key to achieving the desired finish and performance.

Let's look at the options you've considered:

• Synthetic Fluorphlogopite: You noted this gives the brightest white color and medium coverage. However, it's described as synthetic mica that improves sparkling. Since you prefer a non-shimmery finish, Synthetic Fluorphlogopite might provide too much visible sparkle or intense radiance, potentially looking less natural or like "fish skin" as you described.
• Mica: You mentioned Mica gives a greyish-white tone, large particle size, and good coverage. The greyish tone means you would rely heavily on the Beige Iron Oxides to achieve the correct shade, which could affect the final color vibrancy. While available in matte versions, the "good coverage" might be more than your desired low-medium. Regarding Titanium Dioxide, it's a white pigment and UV filter. You don't need it just to correct Mica's grey tone if you're using Beige Iron Oxides for color, but you could add it for whitening or UV protection if desired.
• Sericite: This powder offers a medium white color, medium particle size, and medium coverage, which aligns well with your coverage requirement. Coated versions (like Silane or Methicone coated) improve texture, adherence, and can offer water resistance.
• Silk Talc Powder (Silane Coated): The description for the Silane coating on Talc is highly relevant to your needs. It provides high water resistance, effectively prevents color change, darkening, or yellowing caused by sweat or skin oils, feels soft and smooth, adheres well to the skin, and is easy to spread. These properties directly address your concerns about oil control, preventing dullness throughout the day, and waterproof performance.

Comparing Sericite and Talc

You asked which is better for preventing dullness, providing a light texture, and good adherence.

• Preventing Dullness: The Silane coating on Talc is specifically highlighted for its ability to prevent dullness from sweat/oil. Coated Sericite also offers good adherence, which helps the powder stay in place and maintain its appearance, but the anti-dullness benefit is more explicitly stated for the Silane Coated Talc.
• Light Texture: Both Sericite and Talc are soft powders, and coatings enhance their feel. Talc is generally known for its very fine, soft feel, contributing to a light feel on the skin.
• Good Adherence: Both Silane coated Talc and coated Sericite are described as having good adherence due to their respective coatings.

Recommendation for Base Powder

Considering your oily skin, the need for strong oil control, preventing dullness from sweat and oil, and high water resistance, Silk Talc Powder (Silane Coated) appears to be the most suitable base powder based on its described properties. Its specific benefits for preventing dullness and color change caused by skin oils and sweat directly address your primary concerns for wear throughout the day.

Matte Sericite (coated) is also a good option, offering medium coverage and a matte finish, but the Silane Coated Talc has a more explicit description of preventing oil/sweat-induced dullness.

Regarding Your Formula and Sunscreen

Your current formula structure is suitable for a loose powder. The combination of a base powder, Allantoin for soothing, MatteSilica™ for oil absorption, and Beige Iron Oxides EasyMix™ for color is a solid foundation.

Regarding your question about using this loose powder formula to make a silicone-free cream sunscreen: No, this formula cannot be directly converted into a cream sunscreen. Cream sunscreens require a different type of formulation involving an emulsion system with oil and water phases, emulsifiers, and specific UV filter ingredients (like Zinc Oxide or Titanium Dioxide) dispersed within the cream base. Your current formula is a dry powder blend and lacks the necessary components and structure for a cream.

However, you could adapt this formula to create a silicone-free powder sunscreen by incorporating appropriate powder-based UV filters such as Zinc Oxide and/or Titanium Dioxide into the blend and adjusting the base powder percentage accordingly.

In summary, for your specific needs, Silk Talc Powder (Silane Coated) is likely the best choice for your loose powder base due to its superior properties for oily skin, preventing dullness, and water resistance. Your current formula cannot be used to make a cream sunscreen, but it could be modified to create a powder sunscreen.