Step 1: Get the complete ingredient list.
Step 2: Look at what each ingredient brings to the product.
Step 3: Figure out what's important in the recipe.
Step 4: Figure out how much you're going to use of each ingredient.
Step 5: Formulate a starting out recipe in percentages and try it.
Step 6: Tweak the recipe to get the skin feel and viscosity you want.
We have our ingredient list, so let's see what each ingredient brings to our product. Try to figure out where you think the 1% miscellaneous category starts!
Water - Our solvent
Petroleum - This is generally found as a yellow semi-solid ingredient used as a skin conditioner and emollient. Prevents transepidermal water loss and offers emolliency. It can be considered an occlusive ingredient.
Hydroxylpropyl starch phosphate - Also known as Structure XL, this ingredient offers emulsification stabilization and thickening. It's non-ionic with a pH of 4.5 to 7. It can be used in surfactant systems and will help boost foam and offer some skin conditioning benefits. It's also reported as making our surfactant products feel creamy. Use at 3% to 10% in the heated water phase or cold water phase.
Dimethicone - A silicone that offers skin conditioning and emolliency.
Fragrance - Smells pretty!
Stearyl alcohol - Like cetyl alcohol, it's a fatty alcohol that will increase emolliency and make our product pearlized.
Shea butter - An emollient. Might be water soluble, might be the regular kind.
Polysorbate 60 - A dispersent, like polysorbate 20 and polysorbate 80. Polysorbate 60 can also be found in food products (like Twinkies!)
DMDM Hydantoin & Iodopropynyl butylcarbamate - The preservatives.
Disodium EDTA - Chelating ingredient.
Cetyl alcohol - A fatty alcohol that increases emolliency and pearlizer for surfactants.
It's usually a safe bet that the fragrance is in the 1% category, so is the dimethicone in the 1% or higher category? I like to use dimethicone at 2%, so let's say everything below that is the miscellaneous listing!
So the main emollient is the petroleum. I don't have access to petroleum, so I'd use one of our butters or oils to make this product more moisturizing and thicker. I like shea butter, but you can use any butter you like, but you might not want to use cocoa butter as that can really thicken a product! I'm going with a 50-50 butter and oil at 10% in the product to see if the thickness is right. It might work, it might not, but I think it's a good starting point.
We know we won't be using the Structure XL at over 10%, so it's safe to say that everything below this is at much less. The shea butter is in the miscellaneous category, which just goes to show you that advertising this as a shea butter lotion is kinda...well, deceptive. The polysorbate 60 is probably there to emulsify the fragrance only, so the Structure XL is pretty important for being able to emulsify all that mineral oil (I'm thinking 10% to start for the oils and 2% to 3% for the Structure XL or so, which seems to be a good amount reading the data sheets.) So everything under the Structure XL should be at 3% or less.
I'm using cetearyl alcohol in this recipe because stearyl alcohol + cetyl alcohol generally equals cetearyl alcohol. If you don't have it, try using cetyl alcohol.
So here's what I'm thinking for this recipe...
POSSIBLE DUPLICATION OF OIL OF OLAY'S IN-SHOWER LOTION
HEATED WATER PHASE
3% Structure XL
HEATED OIL PHASE
5% butter of choice
5% oil of choice
2% cetearyl alcohol
COOL DOWN PHASE
1% polysorbate 20 or 60
0.5% to 1.5% preservative of choice
Weigh out the Structure XL and add it to the water phase. Allow 5 minutes for it to hydrate, mix well, then put into your double boiler and heat until it reaches 70˚C. Weigh and heat the oil phase until it reaches 70˚C. Remove from the heat, then add the oil phase to the water phase and mix very well. Add your fragrance oil to the polysorbate and mix well. Then add it to the lotion, along with the rest of the cool down phase. Allow to cool, then bottle.
Remember that this is a starting point. You might want more moisturizing or less moisturizing or more emulsifier (the Structure XL) or a higher viscosity. If I were to make this for myself, I'd want to include some aloe vera at 10% (in place of the water), a humectant like glycerin or sodium lactate (at 3% or 2.5% respectively), some hydrolyzed protein (about 2% in the heated water phase), panthenol (2% in the cool down phase), and some other things that are good for my skin. I'm not saying this recipe isn't good for your skin, it's just missing some of those things I really like for my skin like humectants (which, to me, are a standard ingredient in lotion!).
Join me tomorrow as I take a look at duplicating Neutrogena's Body Oil!