Making cream from oils and water - Preservatives and Ratios
Question
I am planning to make a cream using rosehip oil, jojoba oil, and water. I have two main questions:
1. Is it necessary to include a preservative in this formulation?
2. How can I calculate the correct ingredient ratios to make a 30ml batch of this cream?
Answer
Subject: Making cream from oils and water - Preservatives and Ratios
Hello,
Regarding making a cream from rosehip oil, jojoba oil, and water:
- Preservatives: Yes, you absolutely need to add a preservative if your formulation contains water. Water provides an environment for bacteria, mold, and yeast to grow, which can spoil the product and be harmful to your skin. This is a crucial step for product safety and shelf life.
- Emulsifier: To combine oil and water into a stable cream, you will also need an emulsifier. Oils and water don't mix on their own; an emulsifier helps create and maintain the emulsion.
- Ratios for 30ml: Providing specific ratios for a 30ml batch is not straightforward without a complete formula. A typical cream formula includes water, oils, an emulsifier, and a preservative, often along with other ingredients like thickeners, humectants, or active ingredients. The ratios (percentages) of each ingredient depend on the desired texture, stability, and properties of the cream, as well as the specific type of emulsifier and preservative used (each has a recommended usage rate).
It's best to start with a basic cream formulation recipe that includes percentages for water, oil phase (your rosehip and jojoba oils), emulsifier, and preservative. Once you have a formula with percentages, you can easily calculate the amount in grams (or ml, assuming density is close to 1g/ml for simplicity in small batches, though weighing is more accurate) needed for a 30ml batch.
For example, if a formula calls for 70% water, 20% oils, 5% emulsifier, and 1% preservative, for a 30g batch (roughly 30ml), you would need:
- Water: 70% of 30g = 21g
- Oils (Rosehip + Jojoba): 20% of 30g = 6g
- Emulsifier: 5% of 30g = 1.5g
- Preservative: 1% of 30g = 0.3g
(Note: This is just an example; actual percentages will vary based on the formula).
I recommend looking for beginner-friendly cream formulation guides or simple recipes online or in cosmetic formulation resources. These will provide you with starting percentages for different ingredient types.