Lotion Formulation Issues: Greasiness and White Streaks

Hello! Regarding the issues you are experiencing with your lotion formulation for dry skin:

1. Residual greasiness and poor absorption: This could be due to the relatively high total percentage of the oil phase (around 19.1%) and the types of emollients or thickeners used, which might feel heavier or more occlusive compared to the Cerave lotion you mentioned, which often uses lighter emollients.

   • Suggestion: Try reducing the total oil phase percentage slightly. Consider swapping some of the heavier emollients like Pentaerythrityl Tetraisostearate or Neopentyl Glycol Diheptanoate for lighter, faster-absorbing options.

2. White streaks when rubbing (Soaping Effect): This is a common phenomenon called "soaping" or "whitening." It happens when solid or semi-solid ingredients in the emulsion, such as fatty alcohols (like Cetyl Alcohol) or certain emulsifiers, become visible as white streaks as the water evaporates during application. You are correct that Cetyl Alcohol tends to worsen this issue, as it is a fatty alcohol with a higher melting point that can contribute to this problem. Glyceryl Stearate can also play a role.

   • Suggestion:
     • Reduce Cetyl Alcohol and/or Glyceryl Stearate: Since you noted Cetyl Alcohol increased the issue, reducing its amount, or potentially Glyceryl Stearate as well, can help minimize the soaping effect. However, these ingredients contribute to the body and stability of the lotion, so reducing them might require adjusting other components.
     • Improve the Emulsification Process: Proper emulsification is crucial. Ensure both water and oil phases are heated to the correct temperature (typically around 70-75°C) and all solid components in the oil phase are fully melted before mixing. Use sufficient and continuous mixing during emulsification to achieve a fine, uniform particle size. Controlling the cooling process (cooling slowly with continuous stirring) can also help stabilize the emulsion and prevent the crystallization of components that cause whitening.
     • Review Emulsifier System: Ensure the primary emulsifier (Milk Lotion Maker) is suitable for the total oil load and the specific ingredients in your oil phase.

In summary:

• For greasiness/absorption: Reduce total oil phase or use lighter emollients.
• For white streaks: Reduce Cetyl Alcohol/Glyceryl Stearate and optimize your emulsification process.

It is recommended to test these adjustments in small batches first. Hope this helps you improve your lotion formula!