Saturday, January 4, 2014

Weekend Wonderings: What's a plasticizer? Can we add BTMS to lotion bars? Why don't I use GSE or Vitamin E as preservatives?

In this post on sorbitol, Marjo asks: I am suddenly obsessed with this plasticizer reference... Sorbitol is one of them. I think cyclomethicone is increasing spreadability so that is a plasticizer too? Or do they also need to do film forming? Are there more like these and would we want them to be in a formulation?

What is a plasticizer? It is an ingredient that increases the fluidity or plasticity of a product or another ingredient. It softens skin, or dissolves or coalesces ingredients. It's hard to declare what is a plasticizer without knowing the product or other ingredients because it's dependent upon that relationship.

One area you see a lot of talk about plasticizers is in nail polish. The main plasticizers in a top coat could be camphor or castor oil, but it doesn't mean we'd want to use those ingredients in something like a hair styling product that offers hold - like hair spray or gel - because dimethicone works better with resins. We add free fatty acids to bars to make them more flexible and, believe it or not, beeswax is a plasticizer in something like a lotion bar because it makes it more smooth and flexible while hardening it. In lotions, we add humectants like glycerin, sorbitol, or propylene glycol or esters to increase the fluidity.

Great question, Marjo!

In this post on lotion bars, Rosi asks: Can we add some BTMS to the lotion bar?

Yes, we can add many different oil soluble ingredients to a lotion bar, but the question becomes why add them? Incroquat BTMS-50 or Rita BTMS-225 can be a great way to harden a bar. I use it as the conditioner and hardener in my conditioner bars and my shaving bars as I don't want a ton of butters or beeswax in either of those products. I also add it to my scrub bar to offer conditioning, emulsifying, and bar hardening. You could add Polawax or other emulsifiers if you wish, and you could add thickeners like cetyl alcohol, behenyl alcohol, or stearic acid as well.

What do these things bring to the lotion bar? They can offer hardening without being too stiff and they might offer more emolliency. Some can offer some slip and glide - like cetyl alcohol - and some might offer a drier feeling to the product, like BTMS-50 or behenyl alcohol. If you're using it in water, it behaves as an emulsifier to turn into a lotion before you rinse it off.

In this post on Using extracts, hydrosols, and botanical ingredients, len asks, Why don't you use natural preservatives such as Vitamin E or grapefruit extract? Is it a price issue. I try to keep my lotions as natural as possible.

I think it's admirable to want to keep your products natural, but neither Vitamin E nor grapefruit seed extracts are preservatives. They are anti-oxidants, meaning they will retard the rancidity of our oils, but they don't protect our products from bacteria, fungus, yeast, or molds, which is what preservatives do.

Related posts:
Preservatives section of the blog
If some essential oils are anti-microbial, why can't we use them that way?
How do anti-oxidants affect the shelf life of our products?
Mechanisms of rancidity
A primer on rancidity


len said...

Good to know. So what natural preservative can I use if making a whipped body butter?

Susan Barclay-Nichols said...

If your body butter doesn't contain water, you don't need a preservative. You only need to preserve things that contain water or that might be exposed to water, like a sugar scrub. You could use an anti-oxidant to retard the rancidity of the oils if you think you'll have the product longer than the oil with the shortest shelf life or if you're using something with a really short shelf life, like unrefined hemp seed oil or grapeseed oil. I'm glad to see you're interested in using preservatives! It makes me so happy!

Marjo said...

interesting susan thank you for your thoughts on the plasticizer!!!!!!