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Shampoo Stability
I made a shampoo batch and checked stability of sample after few days. This batch showed viscosity as per specifications at 25oC. But at 40oC its viscosity decreased drastically. What would be the reason for this loss in viscosity?
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13 Replies
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At higher temperatures the particles possess higher speed and if they become faster it will lead to less viscosity and that’s why it will flow easily.
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But the other shampoo batches did not show any decrease in viscosity at 40oC. This batch which failed in viscosity contains ghassoul clay. Did this ingredient cause the fall in viscosity?
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Prepare the same formula without this clay and check then, if so, try to reduce the quantity in the formula.
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Just out of curiosity, why would you want to put clay into a shampoo?
My best guess on the viscosity problem is that the clay is absorbing some of the surfactants and/or adding to the electrolyte content of the shampoo. -
@Bobzchemist I was thinking that but @prachi92 says that it is OK @ 20C but loosens up at 40. Now thats a bit confusing because if this micelle packing is getting disturbed by clay then why at 40 and why not at 20C. Or at higher temperature the absorption is taking place and not at 20C.
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Bobzchemist this ghassoul clay has many beneficial properties in cosmetics. This batch also contains egg yolk. But the observation was that other batches made with egg yolk and other auxilaries didn’t show any decrease in viscosity at 40oC. Is it that at high temperature some complex is formed which is solubilizing the surfactant structure?
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Egg yolk??? Sounds like a Lush product! Obviously egg yolk is going to completely change as the proteins denature with temperature.
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Other formulations which contain egg yolk are stable at high temperatures. The viscosity issue was only with this particular ghassoul shampoo batch.
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@prachi92, beneficial properties in cosmetics I could understand. But in shampoo? What possible benefit do you think you are getting in the 5 or so minutes this material stays in contact with the scalp?
Assuming you want to make some marketing claims with the clay, my best suggestion is to reduce the clay level down to 0,0001%, so that you don’t have to worry about stability. -
Other formulations which contain egg yolk are stable at high temperatures. The viscosity issue was only with this particular ghassoul shampoo batch.
Let’s look at the chemistry. The yolk proteins denature between 65 and 70C, which is heat and hold temperature, so you’ve basically got boiled egg in your shampoo. Then you add the clay. This is generally speaking an alkaline material (I have several here and some are so reactive as to cause heating of the skin). So, you have organic material in intimate content with alkaline minerals, what do you suspect might happen? -
Actually I am not trying to be nasty or anything, I’m trying to find a way to say this diplomatically, my Aspergers makes this hard work. Have you given careful thought to preservation? The answer to my question above, is “digestion” and clay is a well known risk for bacterial problems. If you have all this organic material as well, in partially digested form, well, it’s going to look like a banquet for any organism that happens on it. I don’t think a simple preservative would be up to the task.
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You can use a sterile clay but you may have problem with the spreading of clay. Eventually, it may will accumulate at the bottom…
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what’s your surfactant system, and what other ingredients have you got in there?
also, how long have you had samples at 25°C?
(I ask because that viscosity loss may simply be much slower at 25°C than it is at 40°C, and as time goes by you may observe it at 25°C too)
also, not directly relevant to this thread, but that egg yolk could potentially be a huge microbiological risk, depending on how much you’ve got in there and whether or not it’s sterilised
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