Castor oil is soluble in alcohol and creates an interesting solubility with beeswax, which is why it is used so much in lipsticks, lip balms, and deodorants. It has a low molecular weight so it penetrates skin easily, and acts as a softening oil. It is a greasy feeling oil with a lot of shine, but can feel sticky (again, this is why it is used so much in lipsticks - it's shiny and it works to keep the oil on your lips and not feathering into fine lines). It is low comedogenic (1 out of 5) and non-irritating. It has acanthotic activity, meaning it can help increase skin thickness.
Ricinoleic acid is an interesting fatty acid. It's a hydroxy acid, which is why it is soluble in alcohol (but not water) and oil. It's a humectant (look at those lovely OH groups!), which is another reason we see it so often in cosmetic products! The ricinoleic acid makes it both a drier type of oil and increases the viscosity of the oil.
Castor oil is an inexpensive oil with a shelf life of up to one year. It is a softening oil but can feel dry on your skin. It is considered a very thick oil - one of the thickest at the homecrafter's disposal - so you might want to save it for those times you really need some serious softening and moisturizing. Castor oil does contain some phytosterols in the form of ß-sitosterol, campesterol, and stigmasterol, so it does offer some anti-inflammatory and itch reducing properties. It doesn't appear to have much in the way of Vitamin E, so you might want to include a titch if you are planning to keep your product around for more than a year! The ricinoleic acid is considered an analgesic and anti-bacterial, and there are some indications it might act as an anti-fungal oil. (Hence the use for a lot of foot products!)
If you're interested in trying the oil cleansing method (OCM) for your face, consider using between 30 to 50% castor oil in an anhydrous mixture of various oils. It's a great addition in a product you want to be water resistant, like a lip stick or zinc oxide, or a heavy feeling moisturizer that will sink into your skin without occluding it. The anti-inflammatory and anti-microbial features might be a good addition for a facial product if you're having trouble with acne - it's low on the comedogenicity scale, so it shouldn't annoy sensitive skin too much.
As an aside, castor seeds contain ricin, which is incredibly poisonous. One seed could kill a child, 6 can kill a horse, 6 to 20 to could an adult, and 80 can kill a duck or a rooster (which really just goes to show that the dose really does make the poison!)
Castor oil is also considered a good laxative, but considering you need about 30 ml to be effective, you don't need to worry much about a lipstick with this oil! (You'll probably use something like 2 or 3 ml maximum in a lip balm, and you're not going to eat all of it in one day, right?)
As a note, you can buy sulfated castor oil, also known as turkey red oil, which is a surfactant that can be used an emulsifier in things like bath oils and bath bombs. I'll be writing more about this ingredient when I get into emulsifiers!
Join me tomorrow for a few ideas on formulating with castor oil.