Sunscreen Formulation Advice

Thank you for sharing your DIY sunscreen experience and questions. It's great that you were able to adjust your formula to achieve a usable texture!

Let's address your questions and formulation goals:

1. Why was the initial texture thick?

The initial thickness and hard-to-spread texture likely resulted from a combination of factors in your water-in-oil (W/O) emulsion formula:

• High Solid Content: Your formula contained a significant amount of dispersed solid particles from the Titanium Dioxide 15nm Liquid (20%) and Zinc Oxide 35nm Liquid (8%). While these are in liquid dispersion form, they still contribute to the overall solid load in the oil phase, increasing viscosity.
• Polyethylene Wax: You included 3% Polyethylene Wax, which is a hard wax used to increase viscosity and provide water resistance. Heating to 70°C might not have been sufficient to fully melt and disperse this wax (which has a melting point around 84°C), potentially leading to incomplete incorporation and a very stiff texture upon cooling.
• Emulsifier System: While Water-in-Oil EZ is designed for W/O emulsions, the balance between the oil/silicone phase (including the carriers from the sunscreens and the wax) and the water phase is critical. Your initial formula had approximately 34% oil/silicone/wax components, which is on the higher side of the recommended range for Water-in-Oil EZ (20-35%). A higher internal phase (water in this case) generally leads to a thicker external phase (oil). However, the high solid load and the wax likely contributed more significantly to the excessive thickness.
• Satin Cream Maker: You used Satin Cream Maker in the water phase. While Satin Cream Maker is a versatile thickener, it is primarily designed for oil-in-water (O/W) or water-in-silicone/oil systems where it thickens the external water or silicone/oil phase. Using it in the internal water phase of a W/O emulsion might not function optimally and could potentially interfere with the Water-in-Oil EZ, contributing to the texture issue.

2. What is the effect of adding LipidSoft™ Lite?

Adding 50g of LipidSoft™ Lite to your 200g batch (approximately 25% of the final formula) significantly increased the proportion of the external oil/emollient phase. LipidSoft™ Lite is a very light emollient that helps reduce stickiness and improve spreadability. By increasing the amount of this lightweight oil, you effectively diluted the solid particles and the thickening effect of the wax and emulsifiers, resulting in a softer, less viscous, and more spreadable texture, as you observed. LipidSoft™ Lite is a suitable emollient for sunscreens and BB/CC creams and is compatible with the other ingredients.

3. Adjusting the formula for easy wash-off, lightweight coverage, and non-greasy feel

To achieve a sunscreen that is easily washable, non-waterproof, lightweight, non-greasy, and provides coverage, you will need to make some significant adjustments, primarily by changing the emulsion type.

• Emulsion Type: Water-in-oil (W/O) emulsions, like your original formula, are inherently designed for water resistance. To make a product easily washable, an Oil-in-Water (O/W) emulsion is generally required. In an O/W emulsion, the oil droplets are dispersed in a continuous water phase, making the product feel lighter and easier to wash off with water.
• Sunscreen Agents: Physical sunscreens like Titanium Dioxide and Zinc Oxide provide excellent broad-spectrum protection but contribute to water resistance. To reduce waterproofness while maintaining physical protection, you could use a lower percentage of a dispersible physical sunscreen designed for O/W systems or combine them with chemical sunscreens in an O/W base.
• Coverage: BB Micro Silk, Silk Mica Powder, and Synthetic Fluorphlogopite are excellent choices for providing coverage, soft focus, and radiance in a lightweight manner, as you included in your second proposed formula.
• Texture: To achieve a lightweight and non-greasy feel in an O/W emulsion, use lightweight emollients like LipidSoft™ Lite, Cyclopentasiloxane, or Dimethicone. Replacing Polyethylene Wax with a softer wax or omitting it entirely would also reduce the heavy, waterproof feel.

Recommended Approach for a Washable BB Sunscreen (O/W Emulsion):

Creating a stable O/W emulsion requires a suitable O/W emulsifier. You could consider using Satin Cream Maker as a thickener in the water phase of an O/W formula, as it is designed for this purpose. You would need to select an appropriate O/W emulsifier to bind the oil and water phases.

Here is a conceptual outline for a washable O/W BB sunscreen, incorporating ingredients you have used or mentioned:

• Water Phase: Water, a water-soluble thickener (like Satin Cream Maker), preservatives (like Mild Preserved Eco or Phenoxyethanol SA).
• Oil Phase: A suitable O/W emulsifier, lightweight emollients (LipidSoft™ Lite, Cyclopentasiloxane, Dimethicone), sunscreen agents (e.g., SPF Protect Ultra™ II, potentially Titanium Dioxide 200nm EasyDisperse or Zinc Oxide 200nm EasyDisperse if formulated for O/W), color pigments (Beige Iron Oxides EasyMix), coverage/texture powders (BB Micro Silk, Silk Mica Powder, Synthetic Fluorphlogopite).

The mixing process for an O/W emulsion typically involves heating both phases separately, adding the oil phase to the water phase while mixing, and then incorporating heat-sensitive ingredients and powders after the emulsion has formed and cooled.

Your second proposed formula, while containing good ingredients for coverage and a lightweight feel (BB Micro Silk, Silk Mica Powder, Synthetic Fluorphlogopite, Cyclomethicone, LipidSoft™ CC), is formulated as a water-in-oil emulsion using Water-in-Oil EZ and Oil-Fix W. This system is designed for water resistance and durability, which goes against your goal of an easily washable product.

To achieve your desired washable, lightweight BB sunscreen, focus on developing an oil-in-water emulsion formula with appropriate O/W emulsifiers and thickeners, incorporating the coverage powders and lightweight emollients you prefer.

I hope this detailed explanation helps you in refining your sunscreen formulation! Feel free to ask if you have more questions.