Saturday, June 22, 2013

Weekend Wonderings: Product contamination and jars, cetyl alcohol and substantivity, and freezing our ingredients

In this post on how much cetyl alcohol to add to BTMS-25, Rosi asks: Will our leave in conditioner get contaminated if we keep sticking our hand into it and applying to hair?

Maybe. I'm always apprehensive about sticking my hand or fingers into any of my products because you never know what is lurking on even recently washed hands. As this post on preservatives and packaging notes, the packaging you choose can make a huge difference in contamination of your products. A more closed system, like a pump bottle, experiences less contamination than a product with a screw cap. If you can use a pump bottle, I suggest using that. Or use a smaller jar.

In the same post, Paradisi asks: Will cetyl increase the substantivity of the other ingredients, or only those already substantive? Why, or why not? And is the cetyl:btms-25 1:1 ratio a rule of thumb, or a necessary balance set out somewhere?

Cetyl only increases the substantivity of positively charged (cationic) ingredients. Non-ionic and anionic (negatively charged) ingredients cannot be substantive. So it can't help something become cationic or positively charged.

The rule of thumb is to add equal amounts of cationic quaternary compounds and fatty alcohols to help boost substantivity. In 1 gram of BTMS-25, we find 0.25 grams or 25% behentrimonium methosulfate. So we add 0.25 grams cetyl alcohol for a 1:1 ratio of behentrimonium methosulfate to cetyl alcohol. If we have 4 grams of BTMS-25, we find 1 gram of behentrimonium methosulfate, to which we could add 1 gram cetyl alcohol.

It's a rule of thumb - adding more doesn't increase the substantivity, but it can't hurt your hair. Fatty alcohols can be very nice oil-free moisturizers for your hair, so those of us who want more emolliency in our product might want to use more than the 1:1 ratio. It also thickens up a product and offers slip and glide.

Having said this, you don't have to use any fatty alcohols with your conditioners. I don't. I find they make my hair feel oilier more quickly. And, most of the cationic quaternary compounds you find will already have a fatty alcohol included - cetyl, cetearyl, or behenyl alcohols - so you don't have to add one.

Related posts:
Fun with chemistry: Anionic, non-ionic, and cationic

In the Weekend Wonderings post, Faith asks: I was wondering if you can freeze hydrovance?

Yes! We can freeze many, if not most, of our ingredients. Make sure your cap is on tight and make sure you leave some room in the bottle for the expansion of water. With something like an oil, we aren't worried about the frozen oils expanding. With water, we are worried. I would make sure you had quite a bit of room in the bottle - say an 1/8 or so of the liquid removed - so the liquid can expand without breaking the bottle. Don't freeze anything in a glass bottle - put it in plastic.

In the grand scheme of things, freezing isn't the enemy of our ingredients - we worry more about heat than cold. Just remember to warm the ingredient up slowly when you bring it out of the freezer by leaving it at room temperature rather than throwing it into the double boiler or microwave. And remember that you might still experience cloudiness with oils and surfactants (thanks to the titer points), so you'll want to warm them up slowly after they come to room temperature to make sure they are well mixed.

This bottle of LSB is supposed to be clear, but it was in the cold for quite some time, and it needs to be warmed up well to reintegrate! This is what I mean by cloud or titer points!

As an aside, "unthaw" isn't a word. Technically, it would mean to freeze something. The word you're looking for is "thaw" when you remove something from the freezer to defrost. This isn't directed at the writer of the question or anyone in particular...just something that bugs me! 

Related post:
Heating, holding, freezing, and thawing ingredients
Chemistry: Titer points
The importance of temperature - an example
Points of interest relating to cold on a snowy Friday

Join me tomorrow for more Weekend Wonderings! 


Faith said...

Hi Susan,

Thanks so much for answering my question about freezing hydrovance. In your answer about freezing products you mention not to freeze anything in glass bottles. I am very curious as to why.


Susan Barclay-Nichols said...

Because water expands when it freezes.