How to formulate a detergent – THEORY pt.2

Now we know the basics about our surfactants (if you haven’t read the previous post, go HERE) now it is time to actually formulate a detergent.

Even if you don’t plan on making the detergent by yourself, reading this might be useful to you in order to understand what’s actually inside your shampoo or other detergents and you will be able to understand if these products are delicate or not 😉

How to formulate a detergent

There are not totally wrong combinations of surfactants: you can mix them just by chance and eventually you will always get a detergent, whatever you do. What could go wrong is that you might get a very liquid detergent or you might get it more aggressive than you expected, but it will still be a detergent!
However there are some rules that, if followed, will give you a good detergent with a good density and the right washing-ability.

Controlling the DELICACY:
So far what we said is that mixing more surfactants will eventually give us a less harsh detergent (of course than a detergent made with a single surfactant keeping the active matter value stable).
We also said that when formulating, the best choice should be:
– an anionic or non-ionic surfactant; it is the surfactant which we will add in our detergent at higher %.
– an amphoteric surfactant; it will make the first surfactant more mild.
extra surfactants: (usually non-ionic) these are used in very low percentage and are added to improve the lather or the consistency of the detergent.
Making this kind of combination of surfactants will give, as a result, a balanced detergent which will be delicate enough (this is of course also related to the active matter %).

Always as a matter of delicacy, if you add certain substances, they act as a protector to your skin (for example proteins, at 1-2%).
You could also think of superfatting your detergent and this low percentage of oil will “use” some of the surfactants making your detergent more mild on the skin. Notice, however, that some surfactants don’t “bear” the presence of oils (even an extra drop of perfume oil can disturb them) and get liquid immediately after you add them to the mixture (for example it is the case of sodium lauroyl sarcosinate).

VISCOSITY:
The viscosity of your product is very important: a water-like detergent gives to our subconscious the feeling that it cannot clean enough (even if it is not so).
The negative thing is that some surfactants, when combined, give a very liquid result.
Luckily there are few combinations of surfactants which work very well in giving you a dense detergent:
– SLES + betaine (an amphoteric surfactant) + salt = very dense detergent. Sodium chloride (salt) is often in commercial detergents, even in shampoos. However if you add too much it can make your detergent too harsh. In my shampoo I use SLES, cocamidopropyl betaine and I never needed to add salt because it was dense enough (sometimes even too much).
SLS + a glucoside (this means a non-ionic surfactant: lauryl glucoside, decyl glucoside are the most common for example).
– sodium lauroyl sarcosinate + pH 5 (acidify your detergent to pH 5, using citric acid in a solution or lactic acid, and the sarcosinate will become thick)

There are also other things you can use in case your detergent is too liquid:
if you have already tried the recipe and you like the result as detergent but it is too liquid, the next time you repeat the recipe you can add xanthan gum to the water of the detergent in order to thicken it up a little bit. However do not use xanthan gum at more than 1% or the detergent will get an unpleasant slimy feeling.

There are also some synthetic thickeners exactly made for surfactants.
The best one so far is Tinovis GTC (Inci: Acrylates / Beheneth-25 Methacrylate Copolymer) because you can add it at the end of the making of your detergent and therefore you can adjust the density little by little.

Obviously if you don’t care how your detergent looks and you are fine with washing yourself with a water-liquid detergent… you can use it as it is! 🙂

Now finally to THE FORMULATION

Also the formulation of a detergent is divided in Phase A, B and usually C.

Phase A:
this will be our water phase and usually it contains water and glycerin (remember glycerin is important to keep our products hydrated, this is because glycerin is highly hydrophilic).
In case you want to add xanthan gum you have to add it now (also some synthetic thickeners have to be added in beginning so be sure to read the data sheet of your raw material in advance! 🙂 ).
You also add here any hydrophilic ingredient: for example you add your preservative (ONLY in case it is hydrophilic of course), your hydrophilic colorant (for example the food grade ones), and so on.

Phase B:
In our phase B we have most of the surfactants: usually we add the surfactant at higher percentage (which is usually an anionic surfactant) and one by one we add the “extra surfactants” which are usually the non-ionic ones.
IMPORTANT: do not add now the amphoteric surfactants (generally the betaine) or your detergent might get ruined (in the way it gets very liquid… once again: a detergent cannot really get spoiled and it will still clean your body even if you do something wrong).
Often I add the perfume and the lipophilic preservative directly here in the mixture of surfactants (of course in case I am not using already an hydrophilic one).
One important thing to notice is that once you add a surfactant to another you are supposed to mix slowly and combine them very well because you add a third one.

Now it is time to pour Phase A slowly into Phase B and mix.
This time we only use a spoon to mix, paying attention to not make too many bubbles (however even if you get too many bubbles, they will disappear with time).

Phase C:
This is the phase where you add the amphoteric surfactant and usually your detergent gets thick here.
If this doesn’t happen you can always add here your synthetic thickener (in case it is the kind that needs to be added in the end) or you can try by adding 1% salt or… once again… you can just use your detergent as it is and try to do better next time. 🙂
In case of shampoo you also are supposed to add at this moment all the hair conditioner substances (which will help your shampoo to not feel harsh on the hair)… but I will make a post specifically about hair shampoo to explain this better 😉

Next post will be a recipe for a detergent and I will also show you how to calculate the ACTIVE matter of your detergent, so stay tuned! 🙂
Have a great day! 😀

 

Sources 

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How to formulate a detergent – THEORY pt. 1

How to formulate a detergent

In this post I am going to talk about the formulation of detergents like face-wash, shampoo, shower gels, bubble bath and so on…

All these detergents are made starting from a family of ingredients: SURFACTANTS.
Surfactants are compounds that lower the surface tension of a liquid and therefore they emulsify the grease and the dirt on our skin and help us to wash it off with the aid of water.

Surfactants can be divided in four groups according to their ionic nature:
– cationic – positive charge when ionized. They are mostly used in conditioners.
– anionic – negative charge when ionized. They are largely used in detergents and shampoos and provide good detergency and lather. In this family we ding: SLS (sodium lauryl sulphate), SLES (sodium laureth sulphate), ammonium lauryl/laureth sulphate, sodium lauroyl sarcosinate, disodium laureth sulfoccinate.
– non-ionic – no charge (unionizable). They are lauryl glucoside, decyl glucoside, coco glucoside, caprylyl/capryl glucoside. These are usually not used in shampoos because they don’t leave a comfortable feeling on the hair (it makes them feel dry) unless they are included in the formulation in small amount (and therefore they work more as foam stabilizers). 
– amphoteric –
 both positive and negative (depending on the pH). These are used a lot in shampoo formulation: specially if combined with SLES they help the shampoo to be thick and they also decrease the irritancy (read this in a relative way 🙂 ). They are for example: cocamidopropyl betaine, lauramidopropyl betaine, coco-betaine, cocamidopropyl oxide.

THE ACTIVE MATTER of a surfactant:
How “strong” do we need our detergent to be? This of course depends to what we aim to make: if we are going to make a bubble bath it will need to have a higher washing ability than a face-wash, which should, on the contrary, be very gentle and delicate. The washing ability of a detergent is determined by its “Active Matter” coefficient: every surfactant has an “active matter coefficient” which is a number in percentage (for example the SLES coefficient is 27%) and this tells us “how much active washing substance there is in our SLES… and in this case it is 27%”. This is because the liquid surfactants which we can easily find sold online are usually made of the real surfactant and water (so the active matter is not 100%). You should find out this number from where you purchase your surfactants (if they are not mentioned on the page, send an e-mail to the supplier).

Generally the active matter of surfactant we want in our detergent depending on its aim is this:
Face wash – lower than 10%
detergent for intimate use – around 5%
shampoo – between 10% and 15%
shower gel – between 18% and 20% 
bubble bath – between 20% and 25% (this is because the bubble bath should go directly in the water while the shower gel is supposed to be rubbed directly on the skin)

So now you might be thinking that to make a good shampoo you just need 45% SLES and rest of water and tadaaa… well… NO 😀
It is true that the 45% of SLES plus 55% water would give you a solution with 12.15% Active Matter (45*27(which is the active matter coefficient of SLES):100= 12.15) however there is something very important you still need to know:

In a formulation a single surfactant results more harsh than an equal “active matter %” formulation made with different surfactants.
To make it simple: if you mix surfactants together, you will have a milder results than using the surfactants alone.
A particularly happy mix is SLES with a betaine (usually I have cocamidopropyl betaine) because not only the betaine lowers the harshness of the SLES, but it also thickens the solution.

Generally when formulating you should use:
– anionic or non-ionic surfactant; it is the surfactant which we will add in our detergent at higher %.
– anphoteric surfactant; it will make the first surfactant more mild.
– extra surfactants: these are used in very low percentage and are added to improve the lather or the consistency of the detergent.

To be continued… 😉
[Theory of Formulating a Detergent Part 2]

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