When first starting to make DIY cosmetics, many new formulators look for existing formulations online to follow. While this approach provides a useful starting point, it also introduces a significant challenge: ingredient availability. The process of purchasing beginner equipment and ingredients can be costly, so it’s not uncommon for new formulators to seek ingredient substitutions to avoid additional expenses. However, it’s crucial to understand that any substitution will alter the final product. The formulation will not turn out identical to the original. Some substitutions are more feasible than others, but they require careful consideration.
Key Considerations When Making Ingredient Substitutions
1. Compatibility with the Formulation
Before making a substitution, check if the new ingredient is compatible with the other components of the formulation. This means ensuring it won’t destabilize the emulsion, alter the texture, or cause separation. Compatibility can depend on the ingredient’s polarity, charge, and solubility.
2. Solubility of the Substitute
Solubility is critical in cosmetic formulations. For example, water-soluble ingredients cannot be substituted with oil-soluble ingredients and vice versa. Always confirm that the substitute dissolves in the same medium (water, oil, or alcohol) as the original ingredient.
3. Charge of the Substitute
Ingredients can be cationic (positively charged), anionic (negatively charged), or non-ionic (no charge). The charge affects how ingredients interact. Substituting a non-ionic emulsifier with an anionic emulsifier, for example, can lead to instability or separation of the emulsion. Be aware of the charge of the ingredient and ensure compatibility with other charged components in the formulation.
4. pH Sensitivity
Certain ingredients are pH-sensitive, meaning they work best within a specific pH range. If you’re substituting an ingredient, check its pH stability to avoiddestabilizing the formulation.Preservatives, thickeners, and active ingredients are often pH-sensitive.
5. Function of the Ingredient
Ingredients have specific roles in formulations—such as emulsifiers, thickeners, preservatives, or humectants. When making a substitution, ensure the new ingredient serves the same function. For example, replacing an emulsifier with an emollient will not yield the same result. If the original ingredient acts as an emulsifier, its replacement must also be an emulsifier.
6. Mixing Method & Shear Sensitivity
Some ingredients require high shear mixing to be properly incorporated into a formulation. Others are shear-sensitive and can be damaged or lose efficacy under high shear. If the original ingredient can be mixed at high speeds, but the
substitute is shear-sensitive, the mixing process will need to be adjusted. This can affect the texture, consistency, and stability of the product.
7. Absorption of Carrier Oils
If substituting a carrier oil, consider how quickly it absorbs into the skin. For example, replacing grapeseed oil (a fast-absorbing oil) with castor oil (a slow-absorbing oil) will change the skin feel, slip, and overall user experience of the product. Each oil has a unique fatty acid profile, which affects its absorption, emollience, and skin feel.
Why These Considerations Matter
Every cosmetic formulation is a delicate balance of chemistry. When following a stable, tested formulation, each ingredient plays a specific role in the final product’s texture, appearance, and performance. Substituting ingredients without understanding their properties can lead to a product that separates, feels greasy, or simply does not function as intended.
For new formulators, this process may seem overwhelming at first. However, taking the time to learn about ingredient properties, solubility, and compatibility will improve your ability to make educated substitutions. Formulation is both an art and a science, and understanding these principles is key to mastering it.
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