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Thin layer of foam from liquid hand wash
I am a beginning of cosmetic science. I am working on formulating a liquid hand wash. A thin layer of foam arise from the hand wash overnight. May I know how I can avoid the foam from building up?
Here is my formulation.
SLS
cocamidopropyl betaine
Castor Oil
Glycerin
Glycol Stearate
Sodium Chloride
Citric Acid
Sodium Benzoate
Benzalkonium Chloride
Solubilizer
WaterHence, what is a good practice to dissolve SLS? I am currently dissolving 25-30% SLS in water under 65C-70C.
Thanks!
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10 Replies
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I would suggest that this is just from air settling out of the formulation - you couldn’t see the air bubbles before because your formulation is opaque, but now that it has been allowed to settle they have risen to the top. It will not reduce the future foaming ability of the formula and the foam will break and settle if left for longer.
The best way to avoid this happening is to reduce introducing air into the formulation to start with. Unfortunately there will always be a little introduced with sodium chloride and sodium benzoate with them being solids. You could make a 50% solution of citric acid to adjust the pH which will then prevent the citric acid powder from introducing air.
When you make up your SLS solution, allow it to settle before using so that any trapped air is removed. You should also be using a very low mixing speed when handling surfactants to prevent foam production, especially when first introducing into water. A paddle stirrer will provide more effective mixing than a propeller-type stirrer, as a propeller-type draws the mixture down from the surface, which will also pull air in with it. On a small scale you can also try pouring some of your larger quantity ingredients down the side of the container as you add them so they enter the main mixture slowly (like you would pour a beer).
Hopefully those suggestions reduce the problem!
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I noticed a couple of issues with your formula.SLS is anionic and is not compatible with the cationic benzalkonium chloride. Use a different preservative.Castor oil (or any oil) won’t help with the foaming performance of your hand wash in use. -
@klangridge Thank you for your advice. I will try to avoid introducing air during formulation.
When preparing SLS solution, will you recommend adding sodium chloride in this process or is it better to add it later on?
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@@ozgirl Thank you for your comment. Benzalkonium chloride acts as antiseptic agent. BKC also help reduce the irritation that may be caused by SLS. https://www.ncbi.nlm.nih.gov/pubmed/11016666
Cocamidopropyl betaine is the foaming agent. I am getting good foaming performance. Will you recommend any other agent to enhance foaming performance?
Thanks. -
Benzalkonium Chloride will be deactivated by anionic surfactants as they interact and may form a precipitate. You may be unable to see this due to the opaque nature of your formulation.The article you referenced takes advantage of this interaction between the two materials as a way of reducing irritation because they are bound to each other an unable to interact with the skin. The abstract does not mention anything about the efficacy of the combination as an antiseptic.
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@Franko If you were to add the sodium chloride to the SLS solution, it would thicken rapidly to a higher viscosity than your finished shampoo formula and therefore be very challenging to handle - generally salt addition is the very last step in shampoo manufacture, even after pH adjustment, because the thickening effect makes further processing challenging.
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@ozgirl Thank you for your information. I will look into this issue and comparing the effect of with and without BKC.
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@klangridge Thank you for your advice. I did experience the challenge of thickened solution. I will add the salt at the very end.
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The primary surfactants are majorly anionic in nature. BAC will work with cationic, amphoteric and non-ionic surfactants but will precipitate when used with anionic surfactants like Sodium Laureth Sulphate .
Then for formulation of anti-bacterial hand soap there could be two pathways.
1. To use cationic, amphoteric, non-ionic surfactants or a combination thereof.
2. To use an anti-bacterial agent which is anionic in nature and compatible with amphoteric and non-ionic surfactants as well.
Your suggestions on both the pathways are highly appreciated.
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@MurtazaHakim Do you have any suggestion on anionic anti-bacteria agent?
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