To create a successful and safe lotion, you must follow the process exactly. I cannot stress this enough! And if you don't want to use preservatives, lotions aren't for you.
Oil in water lotions are those with more water than oil. Most lotions are o/w. It has a heated oil phase, a heated water phase, and a cool down phase.
As I only have so much space here, please visit the emollients section of my blog to see the charts I've created. http://swiftcraftymonkey.blogspot.ca/p/oil-butter-posts.html
Glycerin is a humectant, which means it'll draw water from the atmosphere to our skin. It helps increase moisturization. If you don't have it, just increase the water by 3 grams.
Preservatives are not optional, they are essential. If you don't wish to use them, don't make products containing water. An unpreserved lotion has a 3 day life span, and is unsafe to use after that.
I use liquid Germall Plus at 0.5% in the cool down phase. To learn more about preservatives, please vist http://swiftcraftymonkey.blogspot.ca/p/preservatives.html
Grapefruit seed extract, Vitamin E, Vitamin C, and citric acid are not preservatives. They are anti-oxidants and will help retard rancidity of the oils. They will not prevent contamination.
You cannot use the microwave to heat ingredients. Create your own double boiler by putting your containers in a pot filled with water. Find a little rack so they don't touch the bottom.
This recipe should make around 70 ml or a little more than 1/4 cup. Want to make a larger batch? Multiply the amounts to make more! Don't go over 10 times or 1000 g: That's a really large batch!
If you want a PDF of this guide, visit http://dl.dropboxusercontent.com/u/1020026/lotionmakingtutorial.pdf
A few notes: You cannot use volume measurements - tsp, tbsp, etc - for this recipe. It must be weighed. It will fail otherwise.