Saturday, May 7, 2011

Why didn't I use the HLB system to create the lotion in the Garnier product?

You're probably wondering why I didn't use the HLB system to create the lotion in the Garnier product. Let's take a look at it!

The only oils we really have in the mix are the IPP (I'm using it at 1%) and the fatty alcohols. I'm going to use 3% cetearyl alcohol but you can use cetyl alcohol if you want or 1% of each fatty alcohol in the recipe. I have a grand total of 4% fatty alcohols and esters in this recipe. Let's figure out the HLB of this product.
IPP - HLB 11.5 - 1/4 = 0.25 x 11.5 = 2.875
Cetyl alcohol - HLB 15.5 - 3/4 = 0.75 x 11.625
The required HLB for this product is 14.5! Wow!

If we do the math using the formula, we find we need about 29% glyceryl stearate and 71% PEG-100 stearate (if you want to be picky, we get 28.67% glyceryl stearate and 71.33% PEG-100 stearate, but I rounded it to 29% and 71% to get a total of 14.45).

We could use 4% emulsifier here (1.16% glyceryl stearate and 2.84% PEG-100 stearate) or even 2% emulsifier (0.58% glyceryl stearate and 1.42% PEG-100 stearate) or 5% emulsifier (1.45% glyceryl stearate and 3.55% PEG-100 stearate) but none of us have scales that good! So it might be easier to use another emulsifier for this product.

But here's the problem. If you change the high HLB emulsifier, ensure that it's higher than 15. If you use two emulsifiers that don't add up to 15 total, you'll never get a combination high enough to emulsify this product. For instance, if you use glyceryl stearate (HLB 3.8) and laureth-4 (HLB 9.7), you get a total of 13.5, which isn't enough to emulsify our oil phase of 14.5! You have to make sure you have two emulsifiers that will total well over 15 to make sure we can get a combination of emulsifiers!

We could use 24% glycol distearate and 76% PEG-100 stearate to get an HLB of 14.528, which means with 4% emulsifier we'd need 0.96% glycol distearate and 3.04% PEG-100 stearate and with 5% emulsifier we'd need 1.2% glycol distearate and 3.8% PEG-100 stearate. With 2% we'd need 0.48% glycol distearate and 1.52% PEG-100 stearate.

Because these are fairly weird numbers and don't round up well, I felt it was easier to use Polawax or e-wax as the emulsifiers for this product.

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