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The fragile salt curve
It seems to me that salt-thickening a shampoo is only possible with relatively simple shampoo formulae.
I have an all-purpose base that makes a fine shampoo and salt-thickens easily, provided that it is kept simple. Every addition reduces its ability to thicken. I find that adding dispersed silicones, condensed resins, and any kind of organic matter, means I have to use thickeners. Coffee for instance. I just tried coconut milk, same effect. -
6 Replies
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Yes, this is correct. Salt thickening is the result of the composition and structure of the detergent micelles. Anything that you add to change the micelles will change whether salt can thicken the system or not.
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agree totally: any change causes change in mixed micelles likely in CMC and geometry.:
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My conclusion after trial and error is that when you add stuff to a simple formula if you change the fluidity (I mean to make it look as a detergent instead a gel) salt just can’t rearrange the micelle. It will thicken it but you need much bigger quantities. The easy way is to increase the % of thickening surfactants and cut out salt.
It will be interesting to see how and why the micelle is rearranged under different materials, I’ve never found a paper or an investigation about this. Maybe the R&D of surfactants manufacturers will have the info, but I doubt they are allowed to share.
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I found that once you use organic materials in the shampoo, adding salt just makes things worse. The problem with understanding why, lies in the nature of the addition. For instance, I can’t really find a definitive analysis of the nature of brewed coffee. It has hundreds of substances in it.
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Yes, but my guess is the micelle won’t change it’s shape that much. If it did we would notice a more radical change under the addition of different substances (and it’s a big guess).
It would be cool to see it under a microscope, I’ve only seen charts, and of the most common stuff. Have you tried asking manufacturers?. Maybe companies like Hallstar of Stepan could provide some info. Sometimes when you mail the local R&D they answer.
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The key is changes to the CMC as salt or NaCI lowers the former thus producing more micelles in the bulk of the solution:increased micelles means tighter packing and increased viscosity.You can prove this to yourself via measuring surface tension as a function ofSAA concentration using the ring method,SAA suppliers do this routinely:I did hundreds at GAF before they sold their SAA business,
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