So now we know how to combine (and why to combine) the different surfactants… but how to calculate the Active Surfactant Matter we want in our product? (which also mean: how much surfactant we have to add to our product to have the surfactant concentration we want to obtain?).
As I already explained the Surfactant Matter of a liquid surfactant which we buy is not 100%: the surfactant is made of the Surfactant Matter and Water (and probably other ingredients like glycerin, for example); therefore every surfactant we buy has a “Active Surfactant Matter” percentage which is what we have to consider.
As I wrote in the previous posts about formulation of detergents (shampoo, bubble bath, shower gel, face wash), the amount of the TOTAL Active Matter of surfactants has to vary according to the purpose of our detergent.
Generally this is the scheme:
– face wash: <10%
– detergent for intimate use: <10%
– shampoo: 10%-15%
– shower gel: 15%-20%
– bubble bath: 20%-25% (in case you really use it only to make bubbles in the bath tub and you never use it directly on your skin, you could even reach 35%… but I don’t suggest it).
Now let’s learn how to formulate the detergent.
Let’s say we want to make a shower gel, with an Active Matter (once again, the effective concentration of surfactants) around 18%.
We have also already decided which surfactants we want to use:
– Sodium Lauroyl Sarcosinate (Concentration 29%)
– Cocamidopropyl Betaine (Concentration 36%)
– Lauryl Glucoside (Concentration 52%)
There are two different approaches in the formulation to obtain 18% Active Surfactant Matter:
We can choose which share/quota of the total ASM (active surfactant matter) we want to give to each surfactant.
For example this is my choice:
Sodium Lauroyl Sarcosinate 10
Cocamidopropyl Betaine 5
Lauryl Glucoside 3
Total ASM = 18 (as decided)
Now we need to calculate the effective grams of each surfactant that we need to add to our shower gel formula:
We divide the quota of each surfactant by the ASM of the surfactant (in decimals: the ASM of each surfactant is a percentage so if it is 29% we divide per 0.29 OR we divide per 29 and multiply the result for 100… up to you).
Anyway it is easier done than said:
Sodium Lauroyl Sarcosinate (29%) = 10/29*100 = 34,44 (you can add 34.50 gr)
Cocamidopropyl Betaine (36%) = 5/36*100 = 13.88 (you can add 13.50 gr or 14 gr)
Lauryl Glucoside (52%) = 3/52*100 = 5.76 (you can add 5.5 gr)
You can also reason the other way around: you try to guess approximately how much grams of surfactants you want to add to the detergent and then calculate the effective total ASM; if the result is not close to 18% total, you change the grams and calculate again until you are satisfied.
For example this is my initial choice:
Sodium Lauroyl Sarcosinate 40 gr
Cocamidopropyl Betaine 15 gr
Lauryl Glucoside 5 gr
Now I calculate the total ASM of the detergent:
Sodium Lauroyl Sarcosinate (29%) = 40*0.29 = 11.6
Cocamidopropyl Betaine (36%) = 15*0.36 = 5.4
Lauryl Glucoside (52%) = 5*0.52 = 2.6
Total ASM = 11.6+5.4+2.6 = 19.6
I can either decide that 19.6 is fine for me or I can decide to lower a little bit the grams or one or all of them and recalculate the Total ASM.
I decide to calculate again changing the value of grams:
SLS (29%) = 35*0.29 = 10.15
Betaine (36%) = 14.5*0.36 = 5.22
Lauryl Glucoside (52%) = 4*0.52 = 2.08
Total ASM = 10.15+5.22+2.08 = 17.45
Now I decide it is fine and I can proceed in the formulation of the Shower Gel! 🙂
Here I post a list of the most common surfactants you can purchase online, with their average Concentration (ASM) and for the most common I will add also few words on how to use them:
(Notice that the value may vary of few points % so the best thing would always be to ask the supplier which is the precise percentage for the exact batch of surfactant you are purchasing: suppliers always have this information, so you are not asking for something impossible; however you can also use these data 😉 ).
IMPORTANT: surfactants may have different commercial names from the substance they are, therefore always check the ingredients list when you purchase 😉
Sodium Lauroyl Sarcosinate – anionic (29%)
One of the most commonly used eco-friendly surfactants. Improves the foam of other surfactants (specially betaines) making it more smooth and soft. It becomes viscous at pH 5, but only if used in high percentage in the detergent (so remember to acidify your detergent with drops of lactic acid or citric acid). It becomes liquid if in contact with oils (perfume oils included) so synthetic thickening agents or xanthan gum have to be used (you have to consider this in the formulation because the xanthan gum goes in the water phase). Not good in shampoos.
SLES – Sodium Laureth Sulfate – anionic (27%)
It becomes very dense once combined with betaine and salt (betaine can be enough). It is very good in shampoos because it has high wetting properties.
It is not eco-friendly.
SLSA – Sodium Lauroyl Sulfoacetate – anionic
It is not aggressive (this term of course is relative) and it is a powder. It is good if used in the making of Bubble Bars (recipe soon ok 😉 ?)
Sodium Lauryl Glutamate – anionic (36%-40%)
Very delicate and used in products for kids. Unfortunately it tends to melt down the viscosity of many other surfactants (therefore formulate accordingly).
Sodium Comopolyglucoside Tartrate/Citrate – anionic (30%)
Delicate and eco-friendly. Used in products for kids and for people who have very sensitive skin. Very low viscosity.
Cocamidopropyl Betaine – amphoteric (30%-38%)
Alone it is not delicate but it makes other surfactants more delicate (specially anionic surfactants) in a ratio of 1:3 or 1:4 with the primary surfactant of the recipe. It is eco-friendly. Combined with SLES it is a viscosity builder.
Disodium Cocoamphodiacetate – amphoteric (36%-40%)
Delicate. It is used in shampoo because it has conditioning properties to the hair (however for thin hair it might be too much). It doesn’t burn the eyes (therefore it would be good in a shampoo for kids or in a face wash). Usually it is used around 5%.
Lauryl Glucoside – non-ionic (50%-53%)
It is a thick, white paste so it needs to be heated a bit to be combined with other surfactants; the good news is that it helps the viscosity of the final product. It is quite delicate and it reduces the harshness of the primary surfactants. Usually added in low percentage.
Decyl Glucoside – non-ionic (63%-63%)
Good foam booster. Unfortunately it tends to liquefy the other surfactants. Usually added in low percentage.
Coco Glucoside & Glyceryl Oleate – non-ionic (50%-55%)
This is a combination of the surfactant Coco Glucoside with Glyceryl Oleate (Glyceryl Oleate is the ester of glycerin and oleic acid. It is produced from oils that contain high concentrations of oleic acid, such as olive oil, peanut oil, teaseed oil or pecan oil. Source Here), which limits already the harshness of the first. It is added in low percentages (3%-4%)
Lauryl Glucoside and Cocamidopropyl Betaine (43%)
This is made of already two combined surfactants
Coco Betaine (29%-33%)
Coco Glucoside (51%-53%)
Disodium Laureth Sulfoccinate – anionic (35%)
Hope this was clear enough 🙂
Next time I will show a full recipe of a detergent (I still have to choose between a shampoo and a face wash but anyway sooner or later I will post both).
If you want more posts about how to formulate Shampoos check HERE
Let me know if you have any questions 😉
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.