First you really clean up well your kitchen sink. . . just kidding.
But in the good old days it might just had started that way, now with modern technology and ingredients it has became more difficult.
For an emulsion all you basically need is those three ingredients: (1) Water. (2) Oil. (3) Emulsifier
Distilled water is recommended if you want to have a product free of bacteria.
Some products are not emulsion and based on oil only. Those are very simple to make, all you need is grease and oil of different consistency and you mixes them to arrive at your favorite consistency. The better known is Petrolatum, Lanolin and cholesterol sold under the trade name Eucerin. The composition is not exactly but very close to 70% Petrolatum, 20% Lanolin and 5% Cholesterol. The reason cholesterol is use in that formulation is to reduce the quantity of Lanolin. The benefit of lanolin on your skin is the cholesterol but pure Lanolin at the time this formulation was developed, (a century ago) Lanolin was smelly but the cholesterol when extracted from it was not, but Cholesterol was more expensive. I think you get my point. Cost is the number one concern of the skin care industry. They have to pay for expensive ads!
Now back to making it: First you weight all your ingredients, put them all in a container and slowly heat them to approximately 75 degree Celsius and keep turning it, a spoon will do! After everything is melted let it cool and keep tuning it until it solidify. . . et voila! You have made your first face cream.
Now you can change the petrolatum which is really bad for your skin by Cocoa butter, Lanolin for Avocado or Olive oil until you gets the consistency you want. You can experiment with any kind of product as long as they are all fat. One solid one liquid two solids five liquids whatever suit your fancy.
Now the more complex products: Emulsions. As I said before there is three mandatory ingredients
Water, Oil there literally thousands of ingredients, again Avocado, Almond, Cocoa Butter, Shea butter, Olive oil, Lard, it as been done, after all what is Mink oil? Mink oil is oil extracted from mink cadaver after the removal of their fur. they cook them up and skim the oil from the top. Same as Emus Oil, Pig oil is called Lard. I think I could cook with lard. My mother did it, but I will not try Mink fat! No way José! Anyway try to stay away from animal and mineral oil by products. The third ingredient is the emulsifier is absolutely needed to bind oil and water. Everybody who learn cooking know that egg yolk is a good emulsifier, it bind water to oil in sauces, but is not a very good choice for Skin Care.
A better choice is Wax. You can purchase emulsifying wax and use between 6% to12 percent of it, or use the two or three component usually found in it: Stearic acid, 60% 40% Cetearyl Alcohol use 6% to 10% of that mixture in the oil phase. Yes, you have at least 2 phases: the oil phase where all the fatty ingredients in a container where they will be heated to approximately 75 degrees Celsius and the water phase where the entire water soluble ingredient will be heated at the same temperature. The water phase is where you put all your Vegetable extract, Plants, Flowers extracts etc. Be careful extracts are usually dark green yellowish brown and they will very fast color your cream. Also they might be heat sensitive and cannot be heated, in this case you will have to wait until the whole thing cool down before you can introduce them in your formula. Ok I went ahead of myself, let me back track. Now you have your water and oil phase ready you heat them both to 75 degrees Celsius and you mix them together and turn them continuously until the whole thing cool down to 40 Celsius. And now is the time to ad your heat sensitive product. At this point you can also ad your preservatives and stabilized your formulation with 0.5 to 1% of Triethanolamine, (TEA) it make the cream smoother.
If you like to cook you will love to make your own Skin Care products.
Mike A. Hegi Senior Skin Cosmetic Formulation Chemist
The Skin Society
Morgellons Research Foundation