Sunday, January 4, 2015

Weekend Wonderings: Amount of active in our ingredients?

In this post, Iron chemist: Sodium lactate, Matt asks: When you say "I use sodium lactate at 2.5% or lower in my products because at 3% it can make you sun sensitive" Do you mean the total concentration of sodium lactate should not exceed 2.5%? I have the liquid version which is a 60/40 blend of sodium lactate/water so I could use up to 4.15% and still be sun safe correct?

Yes, we take into account the active amount of the ingredient when we have guidelines like this, so using 4.15% of the bottle of sodium lactate you have would give you 2.5%. I tend to use the sodium lactate at 2.5% because my hand could slip when I'm formulating, and I could easily have 3% or higher in a couple of drops. 2.5% means I'm quite below the maximum suggested usage rate but well within the guidelines of using it as a great humectant.

Which leads to another question - what's the deal with active amounts of ingredients? We see this with a lot of our liquids, especially surfactants. For instance, you mention your sodium lactate is 60/40, meaning 60% sodium lactate and 40% water. So when we use 2 grams of this sodium lactate, we are only getting 1.2 grams of actual sodium lactate, the rest being water and (probably) preservative.

If you see the suggested amount of a surfactant - let's say SLeS - listed as "x% is the maximum usage", then that relates to the active amount of that surfactant. I use Stepan Steol CS-230, which contains 26% active SLeS and is a 2 mole version. For SLeS, we find mild to moderate skin irritation at 10% active. So if you used 40% SLeS in your body wash, you'd get 10.4% active SLeS in your product, which could cause some mild skin irritation. You wouldn't want to use that much of one surfactant in any product, so it's safe to say that this is a less irritating surfactant than SLS and on par with most of the others we'll be investigating!

When I write a recipe, I'm writing it for the ingredients I have in my house, which are the same supplies you'll find at your favourite retailer. When I use SLeS at 10% in a recipe, I'm using 10% of the ingredient as it pours out of the bottle. It might then contain 2.6% active SLeS or 8% active SLeS. I'm using the product as I see it, not as it breaks down into active ingredients. If you want to figure that out at home, then feel free to do so. You can generally get the information from your supplier about the active amount. I'm just looking at the bottle and using it that way.

6 comments:

Matt said...

Thank you, Susan

I have been following your blog since 2009 and it has been an invaluable source of information for me.

Thank you for all the hard work you put into this awesome blog.

Susan Barclay-Nichols said...

Hi Matt. Thanks for your kind words. I'm happy to be of service!

Anonymous said...

Hi dear Susan, Happy new year!!!!

A question, do you have a recipe of shampoo with sodium laureth sulfate?

Thanks

My best regards

Susan Barclay-Nichols said...

Hi Anonymous. Please please please put your name on your posts in the future because anonymity can breed a less than friendly community.

Any of my recipes can be used with sodium laureth sulfate. Take a look at the hair care section and just substitute the SLeS for any surfactant. Take a look at this post I wrote on Thursday for more information.

glamaris said...

The information in this post is so important if, like me, you get to reading suppliers' webpages about Acme's ingredient ABC being X% active and then reading recipes that call for X% ABC. It's easy to over-think it and wonder if you need to be calculating out how many grams of Acme ABC equals X% active ABC for the recipe you want to make!

I didn't notice a link to this post in the FAQs, but it might be a good addition under the General Questions section. :) Thanks so much for clarifying this for us over-thinkers!

Glam

Susan Barclay-Nichols said...

Great idea! Thank you, glamaris!