Tuesday, March 3, 2015

Formulating with soy bean oil: Creating a foot cream (part one)

Yesterday we took a look at soy bean oil. I thought we could take a look at a few recipes in which soy bean oil would be a great addition!

For some people, soy bean oil might be a little greasy for the hands, but it's perfect for a body lotion or foot lotion! Let's make a moisturizing foot cream with soy bean oil. Why include it here? Because it offers great moisturizing with all that oleic and linoleic acid, great softening with all that Vitamin E, and reduction in swelling with all those phytosterols. And those things all feel pretty lovely on our feet.

I think I'll use a body butter type recipe for this foot cream because it's rich and decadent and feels absolutely lovely. Here's the starting recipe I'll be modifying...

60% water
2% sodium lactate or glycerin

10% oils
15% shea butter
6% emulsifier
3% cetyl alcohol

0.5 to 1% preservative
1% fragrance or essential oil blend

When making a foot cream, the first thing I think about is viscosity. How thick should this be? And my answer is always this - very thick! I want something I can slather on to my feet and cover with socks, and you can't slather on a thin lotion. Nope, I want something thick and luxurious for my feet. So I think I'll make a low water product with loads of butters and stearic acid as the thickener.

I can use any butter I like for my feet, but I think I'll go with cocoa butter because it's a great barrier ingredient and occlusive. I'll choose soy bean oil as the oil for the reasons I listed above. I think I'll add some dimethicone as a barrier protectant ingredient in the cool down phase as well. And I'm using stearic acid as the thickener. There! My oil phase is decided!

How to figure this out? If I look at the recipe above, I'll use 8% soy bean oil and 2% dimethicone as my oil amount, 15% cocoa butter, and 3% stearic acid for the cetyl alcohol. I will up my emulsifier of choice, Polawax, to 7% to reflect the 25% rule.

The rule for Polawax - and only for Polawax - is that we use 25% of the oil phase as the emulsifier. So if we have 28% oils we would use 7% Polawax. This is only applicable to Polawax. If you are using another emulsifier, please check the suggested usage rate. 

This would be a great place to use Ritamulse SCG as the emulsifier. If that's your choice, you would want to use 8% in the oil phase and remove 1% from the water phase. (If you don't know why I'm removing water from the water phase, please read this post...) You could also use Incroquat BTMS-50 (not BTMS-25) as the emulsifier, but reduce it to 6% and add 1% to the water phase.

All right! We have an oil phase that looks like this...

8% soy bean oil
15% cocoa butter
7% Polawax
3% stearic acid

2% dimethicone

Join me tomorrow as we figure out the water phase for this thick and decadent foot cream!

1 comment:

Paige B said...

Isn't the oil phase a bit high for Ritamulse? You have 25% oil/butter/silicone, but also 3% stearic...doesn't that count as 28% oil phase? I love Ritamulse (or Ecomulse, or in my case, the equivalent by mixing up the individual parts myself), but I always worry about separation I even approach 25% oils. Personally, I really like LotionPro. It emulsifies high oil phase pretty reliably at only 5%, and it's considerably less expensive than Polawax. Polawax is awesome, don't get me wrong, but I do find it a bit greasy for my taste, so given the price-point and the fairly large percentage required, it's rarely my go-to, even if it is extremely reliable.

As an aside, I had some glyceryl stearate and didn't want to buy Ritamulse/Ecomulse on top of that, so I got some sodium stearoyl lactylate and some sodium behenoyl lactylate (SBL). I already had fatty alcohols, and the percentages of each ingredient in Ritamulse/Ecomulse are readily available, so I make it up myself. I got the SBL as an experiment to see if it worked the same as the stearoyl lactylate. I've only done a small test batch and one small moisturizer recipe, but so far, it seems to work. If I can find the HLB of SBL I might do some calculations and see about using the same ingredients in different proportions to emulsify higher oil-phase recipes.