O/W Emulsifier Calculation and HLB

Subject: Basic Knowledge about Emulsifiers

Dear Myskin Team,
Thank you for your questions. We appreciate you reaching out.

Regarding your questions about emulsifiers:

1. Calculating Emulsifier Quantity for O/W Formulations:

   • As the staff mentioned, there isn't a single, simple calculation based solely on the percentage of oil (10%, 25%, or 30%). The required amount of emulsifier depends heavily on the specific emulsifier(s) you choose.
   • Each emulsifier has a recommended usage rate (often provided as a percentage of the total formula, e.g., 1-5%) and a maximum capacity for emulsifying oil. This information is typically found in the product details or technical data sheet provided by the supplier.
   • Formulators usually start by selecting an emulsifier or a blend of emulsifiers suitable for O/W emulsions and using them within their recommended usage range.
   • The total amount of emulsifier needed is influenced by the percentage of the oil phase, but also by the desired viscosity, stability, and the efficiency of the chosen emulsifier(s). Higher oil percentages often require higher emulsifier percentages, but the exact amount is determined through practical testing and observation of emulsion stability over time and under stress conditions (like temperature changes).
   • Using a blend of emulsifiers is common practice to achieve better stability and texture. The ratio within the blend is often guided by the HLB concept (see point 2), but the total percentage of the blend in the formula still depends on the factors mentioned above.
   • In summary: Start with the recommended usage rate of your chosen O/W emulsifier(s). The exact percentage needed for 10%, 25%, or 30% oil will vary depending on the specific emulsifier's efficiency and capacity. Practical testing is essential to determine the optimal amount for stability and desired texture.

2. Choosing Emulsifiers and the HLB Concept:

   • You are right, the HLB (Hydrophile-Lipophile Balance) system is a very useful concept for choosing emulsifiers, especially when using blends.
   • What is HLB? HLB is a numerical scale (typically 0-20) that describes the balance between the water-loving (hydrophilic) and oil-loving (lipophilic) parts of an emulsifier molecule.
     • Low HLB (e.g., 3-6): The emulsifier is more lipophilic (oil-soluble). These are generally better for creating Water-in-Oil (W/O) emulsions.
     • High HLB (e.g., 8-18): The emulsifier is more hydrophilic (water-soluble). These are generally better for creating Oil-in-Water (O/W) emulsions.
   • How to use HLB for O/W Emulsions:
     • Required HLB (RHLB): The oil phase itself has a "Required HLB" (RHLB). This is the specific HLB value that an emulsifier or blend needs to have to effectively emulsify that particular oil phase into a stable O/W emulsion. Different oils and oil blends have different RHLB values (e.g., mineral oil might have an RHLB around 11, while some natural oils might be higher). You often need to look up or calculate the RHLB of your specific oil blend.
     • Choosing/Blending Emulsifiers: Once you know the RHLB of your oil phase, you choose one or more O/W emulsifiers (high HLB) whose HLB value(s) match or can be blended to match the RHLB.
     • Blending for RHLB: It's common to use a blend of a high-HLB emulsifier and a lower-HLB co-emulsifier (which might still be >7-8, but lower than the primary emulsifier) to achieve the exact RHLB and create a more stable emulsion structure. You can calculate the ratio of two emulsifiers (Emulsifier A with HLB_A and Emulsifier B with HLB_B) needed to achieve a desired blend HLB (HLB_blend) using a simple formula.
   • Beyond HLB: While HLB is a great starting point, it's not the only factor. You also need to consider:
     • The chemical type of the emulsifier (ionic, non-ionic, polymeric, etc.) and its compatibility with other ingredients.
     • The desired texture and feel of the final product.
     • The cost of the emulsifier(s).
     • Regulatory requirements.
   • In summary: For O/W emulsions, look for emulsifiers with high HLB values. The HLB system helps you understand the water/oil balance of the emulsifier and how to blend emulsifiers to match the specific "Required HLB" of your oil phase for optimal stability. However, practical formulation and testing are always necessary.

We hope this explanation provides a clearer understanding of emulsifier usage and selection.

Best regards,
Myskin Team