How to formulate a SERUM

Hyaluronic Acid Serum

We have learnt how to formulate a lotion, but what is and how to formulate a serum? 🙂

There are few rules to follow:
1) a serum is usually a very light lotion (this means usually 2%, maximum 4% fats),
2) it is typically fluid
3) it has a very high concentration of ACTIVE INGREDIENTS.
4) it doesn’t have to be heated (actually this is a consequence of the previous points)
5) the function of a serum is to give an extra boost of good ingredients to your skin (just to be clear: the function of a cream is to be emollient and hydrate to the skin… therefore wishing to create “the ultimate hydrating serum” is like expecting to bake the best cake in the world without an oven: if you want hydration, you make a cream… if you want to feed your skin with an extra-boost of vitamins, antioxidants, anti-aging ingredients and sooo on, you make a serum).

How to proceed:
there is still Phase A and Phase B  but they will be slightly different:

PHASE A – will still contain water, glycerin and a gelling agent (or not, but I will explain this later… so keep reading 🙂 ), but you will have to pay attention to which gelling agent you choose: you need to choose a gelling agent which won’t break down in presence of salts or other tricky ingredients (for example carbopol ultrez 21 is one of these difficult gelling agenta). For instance xanthan gum or hydroxyethylcellulose are good gelling agents for this purpose (in case of hydroxyethylcell. remember the gel is formed only at 70° so you will need to heat your water and, only when it is cooled down, proceed in the making of your serum).

PHASE B – the oil soluble ingredients have to be very few: 1.5 – 4% (maximum!). By this I mean that even your oil soluble active ingredients will be counted in the fat percentage of the serum: for example if you desire to add 1% of vitamin E (tocopherol), you include it in your “maximum 4% count” 🙂
But how to behave with these oily substances in order to have a smooth, silky and specially fluid serum? 🙂
You will need different emulsifiers from those which we have used up to now: you will need actually two emulsifiers (one lipophilic at 0.25% and one hydrophilic at higher percentage) which are liquid and don’t need to be heated!
There are many on the market. Actually you could even use a solubilizer to keep together the emulsion (solubilizers are substances which are used to solubilize small small portions of oils into a lot of water: generally they are surfactants. In case you have a solubilizer at home and you want to use it as a hydrophilic emulsifier: add the oily substances of the serum in your becher and, little by little, add drops of the solubilizer until all the solution in your becher becomes milky white. Then add this solubilized oils into your Phase A).
Just for the record: if you don’t add oily soluble ingredients more than 1-1.5%, you don’t even need to add emulsifiers or solubilizers. This is the easiest and most simple way to make a serum 😀 everything would go in just one phase 😉

PHASE C – actually the Phase C could almost be deleted since you can almost always add the active ingredients directly to the Phase A (do not add them only if you use hydroxyethylcellulose as gelling agent because in this case the Phase A has to be heated and active ingredients are thermolabile).

The percentage of ACTIVE INGREDIENTS in a serum can be extremely high.
Sometimes you could even make a serum using an active ingredient as a gelling agent!
An example is the enriched hyaluronic acid serum which you can find HERE: this is also very easy to copy because there is not even the need of adding an emulsifier.

Let me know if I forgot to explain something or you have any questions.
Have a great day! 😀

Formulating a lotion: Phase A – THEORY pt.3

Here I will be more specific about formulating a lotion.

As I already said the PHASE Aalso called “water phase” or “heated water phase”, is the first step to the making of our lotion/cream.
It is mostly heated even if actually it all depends on the other ingredients we are using: the point is that most emulsifiers need to be heated to 70°C and to emulsify it is needed that waters and fats, read “phase A and phase B”, are also both heated up to this temperature. So usually phase A is heated in a double boiler up to 70°C at the same time of phase B.

What does the phase A contain? 

Any lotion should contain at least 70% water (there is a post on water HERE).
You could also use herbal hydrosols (which doesn’t mean “herbal infusion”) but anyway bear in mind that these waters are mostly expensive and do not have so great properties (IMO better you save your money to buy active ingredients 😉 ).

Glycerin is highly hygroscopic, which means that has the ability to attract and hold water molecules very very tight 🙂
This will be the “magic ingredient” which won’t let your lotions become dry after few days you opened them but will actually keep them moisturized.
As you can imagine, the fact that it is so highly hygroscopic is not only a “plus”: if, for example, you add too much glycerin to your face cream you can be sure that after a couple of hours your face will look bit shiny/oily.
So, the percentage of use is 1.5-5% (1.5% should be the minimum, used for example in creams for oily skin; 2-3.5% is for normal to dry skin; 4-5% is for body lotions).

Gelling agents help the lotion to be slightly more firm but mostly they are used to keep the emulsion more stable (only with a small small number of emulsifiers you should avoid using them).
There are many gelling agents, I am going to speak of those I have used:
xanthan gum, there is of two kinds: normal and transparent grade (which gives a transparent gel): it gives a very slimy gel which doesn’t have the best consistency but it is a great gelling agent which does not “melt down” even if you add a high percentage of “salts” (just keep reading 🙂 ). If you use too much it creates a “film” in your skin and it makes you sweat.
If it is the only gelling agent you have, you could use it at 0.2-0.35%; the best, however, would be to use it as a stabilizer of another gelling agent (the next one for example).
How to use it: I usually take the phase A becher and add the glycerin, then add the xanthan gum and mix with a spatula. When it looks dispersed I add the water little at a time. If you incorporate air while mixing just let the gel rest and the bubbles will go.
Here is a picture of glycerin with xanthan gum just poured on top:
Xanthan Gum Glycerin
carbopol ultrez 21, there are tons of “carbopol…” but I am going to speak of what I know better: I haven’t tried the others well enough to make up my mind about them; what I have read is that carbomers create gels which are slightly difficult to keep stable. This “carbopol ultrez 21” is not too difficult to use and, if you follow some rules, it will give great results.
The bad part is that it is stable only at pH 6: if you rise the pH too much everything will be spoiled and there is nothing you can do to save it. Another bad part is that if you add salts to the lotion, the gel melts down and everything is ruined. When I say “salts” I am not referring to cooking salts (only 🙂 ) but I am chemically speaking, so for example you shouldn’t add too much sodium hyaluronate (hyaluronic acid? 😉 ).
But so why should we use something which could give problems in the formula? Simple: it makes a good gel, it doesn’t give other problems like the white “trail” (? not sure… if somebody can help me with my English I will be glad 🙂 )… I am talking about one thing which happens with certain creams: when you spread it, it doesn’t absorb easily and it actually creates a white “trail”, nothing terrible but still we want to avoid it 🙂 . Anyway, I was saying: this ultrez 21 makes a good gel, good consistency in the cream, good finish… so what to do? Simple! We try to help it to be stable by not leaving it alone!
If you want to leave it alone you can use it from 0.5 to 1%, if you use it with xanthan gum (which is a good stabilizer) then I usually do: 0.2% xanthan gum and 0.3-0.5% ultrez 21.
How to make the gel: if you use it alone just measure the glycerin, add the water, measure separately the ultrez 21 and pour it on top of the water without mixing with a spoon.
Here is a picture:
Water and Carbopol Utrez 21
After a short time it will hydrate and it will “enter” the water: notice that it won’t become a gel immediately but it will rather float inside the water (therefore not making it transparent, like in this picture):
Water and Carbomer after 5 min
At this point you can use an immersion mixer paying attention to not incorporate air, just to make it hydrate more. The water will still be liquid at this time because this carbomer lowers the pH and therefore, not being pH6 yet, it will still be liquid. Don’t worry: add one by one drops of a solution 1:9 of sodium hydroxide and water (one part sodium and 9 parts water) and you will see the water become a gel just in front of you 🙂 . If, instead, you are going to use it together with the xanthan gum then you need to separate the two gels in the beginning: use the xanthan gum as I wrote above but do not add all the water there; in another becher pour the remaining water, add the ultrez 21, wait, mix with the immersion mixer and, before adjusting the pH to 6, mix the “xanthan gel” and the “ultrez 21 water” together. Only now adjust the pH :).
hydroxiethyl cellulose, there are different kinds of this gelling agent, so read the technical card to know at which percentage it should be used. Anyway, according to its density, it can be used from 1% up to 5% (if you are unsure which kind you bought, you can ask your supplier or you can use a middle %: from 1.5 to 2.5% but bear in mind that if you use too much it really becomes too thick). The good thing of this hydroxyethyl cellulose is that it doesn’t have any problem with other ingredients and the gel is not of bad quality either (I don’t love it, but that’s my taste 🙂 also with making lotions you should always try and make up your mind on what you like and what you don’t 🙂 ). The big difference from the other two gelling agents, however, is that it works at 70°C only, so it must be heated. I read different ways of using it, I personally use it this way: I warm up the water in a double boiler, I wait that it reaches 70°C and then pour it while stirring with a spoon (the best would be to have a very small mixer that keeps the water moving while you pour… well, I don’t have it 🙂 ). It becomes a little lumpy (I hope this is the correct word 🙂 ) so after a while I use my immersion mixer paying attention that I don’t incorporate (too much) air. That’s it.

I hope I didn’t forget too much 🙂 Have a good day! 🙂

If you want to add something or explain something better, please share your knowledge 😀