O/W or W/O? In the cosmetic world, we sometimes need to mix oil and water — we use emulsifiers for this purpose. When oil and water are mixed by adding an emulsifier, they form two types of emulsions: oil in water — O/W (Oil in Water) and water in oil — W/O (Water in Oil). Let’s take a look at how these two types differ and when it is better to use which of them.
About this article
This article briefly explains the issue of mixing oil and water — which two types of emulsion arise when an emulsifier is used and how they differ from one another. We will go through the composition of the aqueous and the oil phase, their mutual ratio, and then characterise both types in more detail: spreadability, preservation, electrical conductivity, the number of emulsifiers needed and the way they are thickened.
The aqueous phase can be water or any hydrophilic liquid (for example a hydrosol, floral water) and the oil phase can in turn consist of a lipophilic substance or a mixture of several (for example oils, fatty esters or fatty alcohols). At the same time, it applies that in both types the aqueous phase is present in a ratio of 60–80%.
The two types of emulsion in brief
- Aqueous phase 60–80%
In both types of emulsion the aqueous phase is present in a ratio of 60–80%.
- O/W spreads easily
Oil in water emulsions are lighter and spread easily, because the aqueous phase is the external phase.
- W/O for dry skin
Water in oil emulsions are used in products for dry and sensitive skin and in skin care during the winter period.
- W/O are water-resistant
W/O emulsions are water-resistant, some even completely water-proof — which is why they are used in sunscreens and in most make-up products.
- One emulsifier for W/O
When creating a W/O emulsion, one emulsifier is sufficient, but the number of suitable emulsifiers is limited. O/W emulsions, on the other hand, require the use of several emulsifiers.
- W/O are easier to preserve
Since the aqueous phase in them is hidden in the oil phase, they are easier to preserve and are less prone to microbiological contamination.
Properties at a glance
O/W or W/O — differences
When is it better to use an O/W emulsion and when a W/O emulsion? Let’s characterise these two types in more detail.
Oil in water type emulsion O/W
In this emulsion the oil is dispersed in the aqueous phase. They are used mainly in cosmetic products with a moisturising effect (these emulsions spread easily, they are lighter, because the aqueous phase is the external phase). At the same time, they are used in rinse-off products, because they are easy to wash off. As far as the use of an emulsifier is concerned, they require the use of several emulsifiers.
O/W emulsions are more prone to microbiological activity, therefore they need to be properly preserved. An O/W emulsion shows electrical conductivity.
You can thicken these emulsions (increase the viscosity) by adding natural thickeners such as xanthan gum, konjac powder, carrageenan, etc.
Water in oil type emulsion W/O
In this emulsion, drops of water are dispersed in oil. These emulsions are used in products intended for dry and sensitive skin, but also in products for skin care during the winter period (they can be greasy, heavier, because the oil phase is the external phase). They are most commonly used in creams, sunscreens and in most make-up products (because W/O emulsions are water-resistant, some even completely water-proof). The production of a W/O emulsion is more demanding than the production of O/W emulsions. When creating this emulsion, one emulsifier is sufficient for you, but the number of suitable emulsifiers is limited.
Since in a W/O emulsion the aqueous phase is actually hidden in the oil phase, they are easier to preserve and are less prone to microbiological contamination (we will deal with preservatives and the preservation of products in more detail).
A W/O emulsion does not show conductivity. Thickeners have no effect on the viscosity of W/O emulsions. You will increase the viscosity by using waxes.
Frequently asked questions about O/W and W/O emulsions
Practical questions about both types of emulsion — how they differ, when to use which type, how many emulsifiers you need, how they are preserved and how they can be thickened.
What is the difference between an O/W and a W/O emulsion?
In an O/W emulsion the oil is dispersed in the aqueous phase, in a W/O emulsion drops of water are dispersed in oil. O/W emulsions are therefore lighter and spread easily (the aqueous phase is the external phase), while W/O emulsions can be greasy and heavier (the external phase is the oil phase). In both types the aqueous phase is present in a ratio of 60–80%.
When is it better to use an O/W emulsion and when a W/O emulsion?
O/W emulsions are used mainly in cosmetic products with a moisturising effect and in rinse-off products, because they are easy to wash off. W/O emulsions are used in products for dry and sensitive skin and in skin care during the winter period — most commonly in creams, sunscreens and in most make-up products, since they are water-resistant.
How many emulsifiers do I need for an emulsion?
O/W emulsions require the use of several emulsifiers. When creating a W/O emulsion, one emulsifier is sufficient for you, but the number of suitable emulsifiers is limited — and the production of a W/O emulsion itself is more demanding than the production of O/W emulsions.
Which emulsion is easier to preserve?
O/W emulsions are more prone to microbiological activity, therefore they need to be properly preserved. In a W/O emulsion the aqueous phase is hidden in the oil phase, so they are easier to preserve and are less prone to microbiological contamination.
How do I thicken an emulsion?
You can thicken O/W emulsions by adding natural thickeners such as xanthan gum, konjac powder, carrageenan, etc. Thickeners have no effect on the viscosity of W/O emulsions — there you will increase the viscosity by using waxes.
Do emulsions show electrical conductivity?
An O/W emulsion shows electrical conductivity, a W/O emulsion does not show conductivity.
Conclusion
We believe that we have briefly explained the issue of mixing oil and water for you in this article.
If you know of tricks and ideas that could improve our posts, write to us at [email protected].
You will find emulsifiers, hydrosols, oils, thickeners and preservatives for making your own emulsions in the Handymade range.
