Questions on Natural Preservatives for Eye Area, Iron Oxide in Soap, GuarCat pH, and Vitamin C Serum Layering

Question

I have some technical questions about several ingredients and formulations: I purchased three natural preservatives: Thyme Care, PaeoniaPreserve, and NaturePreserve. I also have EyePreserve. Can the natural preservatives be used for the eye area? I'm asking for natural alternatives. I used Red Iron Oxide - Non Coated in my handmade oil soap. When I lather the soap, the red color bleeds out. Is this normal? Should I use the Coated version to prevent the color from bleeding like dye transfer in soap? Regarding GuarCat™ Weight-less, the product details state "pH must be below 7.0" in the mixing steps section, but the suitable pH range is listed as "pH 3 - 9". Does this mean that during the dissolution step, the pH must be < 7, but after it's dissolved, I can mix it with other ingredients as long as the final product pH is 3 - 9 (meaning it can be above 7 but not exceeding 9)? If I use Stabilized Vitamin C (Natural-C Glycol™) Serum at night, can I follow it with other skincare products like Vitamin B3, Hyaluronic Acid? Since it works well in acidic conditions, I'm concerned that applying other creams might change the skin's pH and interfere with its function. Or is this not a concern?

MySkinRecipes Expert · Accepted Answer

Answers to Your Formulation Questions

Here are the answers to your questions regarding the products you received:

1. Natural Preservatives for the Eye Area

Generally, any preservative approved by the FDA is considered safe for use around the eyes. While natural preservatives like Thyme Care, PaeoniaPreserve, and NaturePreserve are effective for preserving cosmetic formulations, they are not necessarily more gentle than synthetic options. Eye Preserve is specifically developed for use in sensitive areas like around the eyes and is considered more gentle than the natural preservatives you mentioned.

2. Red Iron Oxide Bleeding in Soap

It is normal for non-coated Red Iron Oxide to bleed color in soap, especially if it is not dispersed properly using a high-shear mixer. Non-coated pigments have low dispersion properties. To prevent color bleeding and achieve better color distribution in soap, it is recommended to use coated or ReadyMix™ versions of Iron Oxides. These types are designed for easier dispersion and better color stability in formulations.

3. GuarCat™ Weight-less pH Range

Thank you for pointing out the discrepancy. The correct suitable pH range for GuarCat™ Weight-less is 3-7. This means that the pH should be below 7.0 during the dissolution step, and the final product pH should also be within the 3-7 range for optimal performance.

4. Layering Stabilized Vitamin C Serum with Other Products

Yes, you can layer other skincare products like Vitamin B3 and Hyaluronic Acid after applying Stabilized Vitamin C (Natural-C Glycol™) Serum. To ensure the Vitamin C serum is fully absorbed and to minimize potential interactions or changes in skin pH that could affect its efficacy, it is recommended to wait at least 10-15 minutes after applying the Vitamin C serum before applying subsequent products.