Water in Cosmetic DIYs

Hello Everybody! 🙂

Today I will briefly talk about the water we use in our DIYs and explain how to calculate its amount in our formulation (I have received many questions of explanation 🙂 I thought it was clear but apparently it was not so).


We already know that whenever we use water in our cosmetics, we need to add preservative because where there is water, there is life and therefore bacteria of any sort might be enjoying the swimming poo.l 😀
It is actually NOT ONLY the case: for example there might be bacteria also in powder-form cosmetics… but the rule that if we have water in our cosmetics we need to add some kind of preserving system is not changed (it’s simply… “not only” 😉 ).

However, does any kind of water work fine for our cosmetics?

The water we should use is demineralized microbiologically pure water. This kind of water has a cost and it is usually sold on websites which sell cosmetic ingredients (you can find some links of online shops here).

But why can’t you use tap water?
Tap water is definitely not demineralized, so the minerals contained in it will interfere with the ingredients of your formulation, ruining all the recipe: the minerals in fact are electrolytes and will disturb every electrolyte-sensitive ingredient in the formula.

On the market you can easily find demineralized water (used for ironing), BUT this water is not microbiologically pure.
If water doesn’t contain minerals, bacteria can still grow in it!
As we already know, adding preservative to a cosmetic that is not colonized by bacteria is effective, while adding preservative to a cosmetic which already contains bacteria… is not so effective, instead! 🙂
[This is an example to give a rough idea: if you apply deodorant to a smelly armpit, it won’t work very well, if you apply it to a clean armpit, instead, it might do a wonderful job 😉 ]
So we need to try to make sure that when we make our cosmetics, we don’t use contaminated ingredients! 🙂

If you cannot buy demineralized microbiologically pure water (or if you cannot wait to get it 😀 and you immediately want to make your cream), you should at least boil the demineralized water.
Boiling it (specially if you do it for a short time) won’t make the water microbiologically pure: boil the water at least 20 minutes and then wish for the best 😉

This is NOT a 100% safe method, but it is indeed way better than using demineralized water straight from the bottle 🙂
There is a method called “heat and hold” which consists in heating up the Phase A and Phase B (of a heated formulation, of course) for 20 minutes in order to both kill bacteria (of the phase A) and melt very well all the butters and waxes (of the phase B).

Now to the calculation of water in our cosmetics 🙂

You must have indeed noticed that I never give the right amount for water in my recipes.
I always write “Water to 100”.

“Water to 100” means that we will calculate the amount of water at the end of our recipe and we will calculate it in order to reach 100%
The calculation of water is left in the end because it enables you to make some changes to the recipe.
Changes are always useful or needed: you might not have the same ingredients I have (for example the preservative! You might use a preservative which needs to be added, in order to work properly, at a different percentage than mine!), or you might miss some ingredients completely and therefore you need to omit them.
I will never repeat this enough: it is very important to keep the percentage of use of our ingredients stable.
It sounds difficult but it is not. Let me make an example:

Imagine I have formulated this very basic recipe for a hair gel:

Water to 100
Xanthan Gum 1.5
Preservative (my specific preservative has to be used at 0.5%)
Hydrolized silk proteins 3

In this case water will be calculated in this way: 100 – (1.5 + 0.5 + 3) (these being the amounts of the other ingredients: we are calculating how much grams are needed in order to reach 100%). So the amount of water needed in this recipe is 95 grams.

However a reader might not have Xanthan Gum and might want to try using Hydroxyethyl Cellulose, which has a different way of gelling the water and needs to be used at higher percentage than xanthan gum (understand this is just an example).
Let’s say the percentage of use is 3.5% HC; then the water will be calculated in this manner: 100 – (3.5 + 0.5 + 3) leading us to 93 grams of water.

If I had written the recipe specifying the grams of water needed, the reader might have done the mistake of adding 95 grams of water instead of 93, therefore lowering the percentage of the preservative in the whole formulation, and this wouldn’t make the preservative work at its best!

So it is as simple as this:
whenever you read one of these recipe, just understand that the amount of water is for you to calculate at the end.
Consider all your substitutions, all your modifications and THEN calculate the water you need to reach 100%. 🙂

Hope this was finally clear 😉

For more recipes click HERE 
To learn how to formulate cosmetics click HERE
For a list of online cosmetic ingredients suppliers click HERE 


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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

38 thoughts on “Water in Cosmetic DIYs

  1. Ana says:

    Thank you for your posts and sharing. I still have to learn a lot about making creams… As you said, water is a problem for preserving them. To avoid these problems with the water, what do you think about making a cream only with oils, butters and waxes and a tonic to use previous to the face cream with the soluble components?
    Many thanks!!!


    • It's all in my hands says:

      One more thing to WHY a real cream is better than the use of two separated phases on the skin used one after the other:
      it has been proven that using emulsified phases (like those in a proper cream) keeps the skin more hydrated than doing otherwise. 🙂
      Just use a REAL (vitamin E is NOT a preservative, nor is vitamin C), certified, eco-not-unfriendly preservative and you will be great 😉


  2. giasenablog says:

    Glad to read that you don’t use Vit E or grapefruit as a preservative. Even my supplier states both as preservatives. No sign of the word antioxidant only preservative.


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