SolaStay S1 (INCI Name: Ethylhexyl methoxycrylene) is manufactured by HallStar, Chicago, IL, and is a clear, yellow-orange, viscous liquid that functions as an emollient, sunscreen active stabilizer and sunscreen solvent. It is insoluble in water, but can be dissolved in ethanol and cosmetic esters. It is a solvent for avobenzone (>25%), bemotrizinol (30%), diethylamino hydroxybenzoyl hexyl benzoate (20%), ethylhexyl triazone (25%) and oxybenzone (30%). HallStar claims that this product is the most powerful and robust photostabilizer on the market today. It photostabilizes the combination of octinoxate and avobenzone and works up to 1000 times faster than octocrylene to protect against a loss of absorbance.
Retinol and retinyl palmitate are retinoids that are widely used in topically applied skin care products. Both are photo-unstable and exhibit rapid photodegradation that results in a loss of efficiency.
Work has been done1 to show that when combined with 5% ethylhexyl methoxycrylene, retinol and retinyl palmitate are photostabilized and exhibit no loss of concentration when exposed to UV light. The following formula illustrates how this combination can be used.
2.Disodium EDTA 0.05
3.Xanthan gum 0.20
4.Butylene glycol 2.00
6.Caprylyl glycol, phenoxyethanol,hexylene glycol 1.00
7.Caprylic/capric triglycerides 5.00
8.Jojoba seed oil 3.00
9.SolaStay S1 3.00
10.Shea butter 2.00
11.Sunflower seed oil 2.00
12.Glyceryl stearate 1.35
13.Glyceryl stearate, PEG-100 stearate 2.00
14.Potassium cetyl phosphate,hydrogenated palm glycerides 1.00
15.Titanium dioxide,triethoxycaprylylsilane 0.50
17.Tocopheryl acetate 0.67
18.Caprylic/capric triglycerides, Retinol 0.28
19.Acrylamide/sodium acryloyldimethyltaurate copolymer, Isohexadecane, Polysorbate 80 3.00
Procedure: Stir constantly. In batch vessel, add 2 to 1 to dissolve. Then add 3 and start heating to 60°C. Premix 4, 5 and 6 and add while heating. In separate container, mix 7 through 11 and heat to 80°C. Add 12 to 15 in order. Cool this oil phase to 65°C and add 16 to 18.
When both phases are homogeneous, add the oil phase to the water phase and mix at high shear for two minutes. Homogenize for 10 minutes, resume mixing and start cooling. At 50°C or lower, add 19, then 20. Cool to room temperature and q.s. to volume. This is a light yellow cream with a pH of 6.0. SolaStay S1 and avobenzone can be used together as follows.
1. Water 45.75
2. Disodium EDTA 0.05
3. Xanthan gum 0.15
4. Glycerin 4.00
5. Paraben mixture (CoSept PEP, HallStar) 0.50
6. Phenethyl benzoate 5.00
7. Diisobutyl adipate 5.00
8. Caprylic/capric triglycerides 5.00
9. Ethylhexyl methoxycinnamate 7.50
10. Octocrylene 2.80
11. SolaStay S1 4.00
12. Dimethyl capramide 1.00
13. Avobenzone 3.00
14. Benzophenone-3 6.00
15. Glyceryl stearate,PEG-100 stearate 3.00
16. Glyceryl stearate 0.25
17. VP/Eicosene copolymer 2.00
18. Potassium cetyl phosphate,hydrogenated palm glycerides 3.00
19. Silica 2.00
Procedure: Stir constantly. Add 2 to 1 in main tank. When dissolved, add 3, and start heating to 85°C. Add pre-blended 4 and 5. In a separate container, add 6-12; then 13 and 14. When dissolved, heat to 85°C and add 15-18 in order. When both phases are homogeneous, add oils (6-18) to water phase (1-5). After mixing for 10 minutes, start cooling and homogenize until batch reaches 55°C, then resume sweep mixing until 50°C or lower. Add 19 and replace water lost to evaporation. Product is a light yellow cream with a pH 5.9
1. C Bonda and J Zhang, Photostabilization of Retinol and Retinyl Palmitate by Ethylhexyl Methoxycrylene, Cosmetics & Toiletries, Jan. 2011, p 40-48.
Harvey Fishman has a consulting firm located in Wanaque, NJ, email@example.com, specializing in cosmetic formulations and new product ideas, offering tested finished products.
He has more than 30 years of experience and has been director of research at Bonat, Nestlé LeMur and Turner Hall. He welcomes descriptive literature from suppliers and bench chemists and others in the field.