Friday, May 4, 2012

Question: How do I know how much of an ingredient to include in a product?

I can't believe I haven't answered this question yet, and I suspect that there is a post out there on this topic, but I figure we'll take another look at this idea! 

How do you know how much of an ingredient to include in your product? These are a few of the things I consider...

Before using a product, always look at the suggested usage rate at your suppliers' shop. They should offer a range - 1% to 5%, for instance - for every product. Some are logical - you could use olive oil at 0.1% to 100% in a product - and some aren't - why not use allantoin over 2%? - so ask questions if you don't understand why there's a limit.

For something like allantoin, the 2% suggested rate is about the solubility of the ingredient in our products as well as the functionality of the product. If you use more than 2% on your product, you're going to get too much exfoliation going on as well as those little horrible shards of allantoin that haven't dissolved. We find this with other powdered extracts. For something like chamomile extract, going over 0.5% won't destroy your skin, but it does mean that you'll end up with precipitation at the bottom of your container. For something like papaya extract, you could have way too much exfoliation going on!

You can find suggested usage rates at the Cosmetic Ingredient Review page - look at their ingredients page. Here's a link to their Quick Reference Table.

You might be able to use polysorbate 20 at up to 50% in a product, but do you want that much? If you only need 2% to solubilize an essential or fragrance oil, then you're going to use 2%. This is a pretty logical concept - only use what you need, but it's surprising how often this trips us up when formulating!

It might be okay to use up to 10% glycerin a hair care product (for example, you could use more, if you wanted), but do you want that sticky feeling in your conditioner? Consider how the ingredient feels on your skin or hair. This is the hard one because this really requires you to get to know your ingredients. (I know I harp on about this, but it's really the only way to learn how to formulate - learn your ingredients, how they feel on your skin and hair, how they interact with other ingredients - and you can't learn this by researching! This is a doing thing!)

I really suggest getting into your workshop and applying some of your ingredients neat on your skin. (Note: Find out which ones are safe for this purpose. Oils, hydrosols, liquid extracts, butters, esters, and most humectants are just fine!) Try the different oils on your skin to see which ones you like. Do a blind test or a test with a friend to keep yourself unbiased when it comes to oils.

And experiment. Try that conditioner with 4% BTMS-50, then 5% BTMS-50, then 6% BTMS-50 to see what you really like. Try that shampoo with a different surfactant. Try a different thickener - make one version with behenyl alcohol, make another with cetyl alcohol, and make another with stearic acid. None of these things can be figured out on paper - you really need to try them!

This is a lot more important than it seems. We use our thickeners like cetyl alcohol, cetearyl alcohol, stearic acid, behenyl alcohol, and cetyl esters to make our lotions a little thicker, a little more glidy, a little more tenacious, and so on. It's amazing how much 2% of one of these fatty alcohols or fatty acids can change the thickness and skin feel of your lotions! We use things like Crothix and glycol distearate in our surfactant based products to make our products more viscous, and if you have an especially thin shampoo or body wash, you might use up to 5%!

Related posts:
Learning INCI names
How do I know when to include an ingredient?


melian1 said...

i made the toner for dry skin (from a few days ago), exactly according to the recipe. yet, it looks like the picture of the spray on the right - with a darker bit at the bottom unless i shake to mix (actually, just tilting it back and forth a time or two does it). is this precipitate? did i do something wrong?

Anonymous said...

so, high humidity, less glycerin right?

Susan Barclay-Nichols said...

Hi Melian. You can get precipitation if you add a little too much. It's not a big deal - just shake before using. It could be that the product called for 0.5% but really was only soluble at 0.4% or you could have mistakenly added a tiny bit extra. No worries - it's still great!

Hi Rosi. No, not necessarily. In fact, I live in a really high humidity area and I love to use lots of glycerin in my products. It's up to your personal preference and skin type.