## Monday, April 25, 2011

### HLB system: Answers to working it out!

All right! How did you do with yesterday's challenge to figure out how much emulsifier to use in this recipe? Don't worry - it wasn't a trick question (I always hate those in math exams)!

I've realized this was really silly to post this on Easter Sunday because most of you were enjoying your Easter egg hunting and time with family and friends, so if you want to work this out and not see the answers, click here now! Don't read any further!

BODY BUTTER FOR ITCHY WINTER SKIN WITH MINIMALLY PROCESSED INGREDIENTS
WATER PHASE
25% water
10% aloe vera
10% chamomile hydrosol
10% witch hazel
2% hydrolyzed protein
5% tamarind seed extract
3% glycerin
0.5% allantoin

OIL PHASE
10% soy bean oil
7.5% cocoa butter
7.5% mango butter
7% emulsifier*

COOL DOWN PHASE
0.5% chamomile extract
0.5 to 1% preservative
1% fragrance or essential oil blend

1. Which ingredients have an HLB value?
The soy bean (HLB 7), cocoa butter (HLB 6), and mango butter (HLB 8).

2. How much of each ingredient is in the total recipe?
Soy bean oil = 10%
Cocoa butter = 7.5%
Mango butter = 7.5%
Total oil phase = 25%

3. Divide this by the total oil phase to get a percentage for each ingredient.
Soy bean oil - 10/25 = 0.40
Cocoa butter - 7.5/25 = 0.30
Mango butter - 7.5/25 = 0.30

4. Multiply the percentage by the HLB value. Add them together to get the HLB value of your oil phase.
Soy bean oil - HLB 7 - 7 x 0.40 = 2.80
Cocoa butter - HLB 6 - 6 x 0.30 = 1.80
Mango butter - HLB 8 - 8 x 0.30 = 2.40
So our target number is 7.00

On to our emulsifiers!

1. Find a low HLB emulsifier and a high HLB emulsifier.
I'll go with glycol distearate (HLB 1) and ceteareth-20 (HLB 15.2). You can choose any low and high HLB emulsifiers you like, but I'm going with these ones for this exercise.

2. Work on the percentages to find a total that is very close to the HLB value of your oil phase.
50% glycol distearate (0.5) + 50% ceteareth-20 (7.6) = 8.1. Too high
60% glycol distearate (0.6) + 40% ceteareth-20 (6.08) = 6.68. Too low.
55% glycol distearate (0.55) + 45% ceteareth-20 (6.84) = 7.39. Too high.
57% glycol distearate (0.57) + 43% ceteareth-20 (6.536) = 7.106. Too high.
58% glycol distearate (0.58) + 42% ceteareth-20 (6.384) = 6.964. Just about right! Let's go with this one!

If we're using 4% emulsifiers, we'll need to use 2.32% glycol distearate (4 x 0.58) and 1.68% ceteareth-20 (4 x 0.42). This is kind of an annoying number, but we really don't want to round it up or down or we'll end up with the 60% glycol distearate and 40% ceteareth-20 amounts, which we know equals 6.68, which is too low for our required HLB amounts!

This is where you might consider using another emulsifier so you aren't having to buy some really expensive scale! You can round up to 2.3% glycol distearate and 1.7% ceteareth-20 without seeing too many problems. Or you might consider going to 5% emulsifier, if it's easier (works out to 2.9% glycol distearate, 2.1% ceteareth-20, which would be easier than the original numbers we calculated!). Remember that the 4% is kind of a random number - there's no rule of thumb about using HLB emulsifiers like there is for Polawax.

You won't necessarily get nice round numbers with this system, like 30% one emulsifier, 70% another. It's just as likely you'll get 31% and 69% or 51% and 49%. Play with the numbers until you get the total you want.

3. Rewrite the recipe with the new emulsifiers. Remember to increase your water amount when you decrease your oil phase.

BODY BUTTER FOR ITCHY WINTER SKIN WITH MINIMALLY PROCESSED INGREDIENTS
WATER PHASE
28% water
10% aloe vera
10% chamomile hydrosol
10% witch hazel
2% hydrolyzed protein
5% tamarind seed extract
3% glycerin
0.5% allantoin

OIL PHASE
10% soy bean oil
7.5% cocoa butter
7.5% mango butter
2.3% glycol distearate
1.7% ceteareth-20

COOL DOWN PHASE
0.5% chamomile extract
0.5 to 1% preservative
1% fragrance or essential oil blend

There you have it! If you got it right, kudos to you! If you didn't, that's okay. You just need some practice. And for those of you who see math and shut down thinking you can't do it, I have one suggestion:  -  Don't be afraid of math! It isn't afraid of you. It won't bite or kick you in your sleep. It won't steal your car and take it out joy riding into muddy fields where it can do doughnuts and crop circles! Math is nice!

Let's move on to something a little harder tomorrow - figuring out the HLB values of esters and silicones.

Bajan Lily said...

Ahah! I always wondered what you'd do when you end up above (>7) or below the desired value. It seemed a bit 'extra' to start looking at more fractions of percentages (40.5, .40.65, etc),

if we didn't have any other emulsifiers to use, (and limited scales) could we just use the 7.39 value? Wouldn't too much emulsifier be better than too little?

Ps maths has never been so exciting! Lol

Anonymous said...

What do you do when you want to add an extract in Caprylic/Capric Triglyceride to your Oil Phase. For example, Chamomile Extract in Caprylic/Capric Triglyceride? If the HLB of Caprylic/Capric Triglyceride is 11 and half of it is Chamomile extract and you want to add 2% to your oil phase, DO YOU COUNT THE WHOLE TWO PERCENT AS AN HLB of 11?

Susan Barclay-Nichols said...

Hi Anonymous. Please put your name on your comment or I will delete it. You need to work through the steps of the HLB system as noted in the post above. How much are you adding? 2%, then you need to figure out how much of your oil phase that is, then the HLB of that amount. Please work through the steps above and you'll see what I mean.