Making Creams Part 3

Using Esters in Creams and Lotions

Whilst using natural plant oils is seen as a positive in terms of the marketing of skincare products, creams featuring high proportions of plant oils do not necessarily make elegant products with a pleasant skin feel.

If plant oils comprise all of the oil phase then the cream may feel heavy and greasy on the skin and may not absorb particularly well. Creams with a high plant oil content tend to also provoke the whitening effect whereby the cream breaks when applied to the skin leaving a white residue which can take time to absorb into the skin.

Manufacturers typically add silicones to the formulation. Silicones provide several sensorial benefits to a cream. They can offset greasiness from plant oils, improve the slip and spreadability of the cream, improve absorption of the cream by the skin, and can offset the whitening effect.

However, with the increasing demand for ever more natural skincare products consumers are preferring to avoid creams and lotions which contain mineral oils and silicones.

Fortunately esters provide an alternative to silicones and, as many currently available esters are Ecocert approved, you can look to improve your formulations without compromising your products' natural claims

What are esters?

A compound formed from the reaction between an alcohol and an acid via the elimination of water. Triesters (groups of three esters) form the backbone of many fats, waxes, and oils that have emollient and skin-conditioning properties (Source: A Dictionary of Chemistry, Third Edition, Oxford Paperback, 1996). Almost all of the esters used in cosmetic products are non-irritating and in most cases are quite beneficial for dry skin.

Why Use Esters?

Creams and Lotions based entirely on plant oils can feel greasy and heavy on the skin. They can also be difficult to absorb and more often than not can provoke the phenomenon known as soaping when the cream is applied to the skin (the emulsion breaks leaving the water to absorb into the skin and leaving the emulsifier and oils on the surface

What are the properties of esters?

Esters offer the opportunity to fine tune your cream or lotion to achieve the skin feel you want.

Esters can determine how light or rich your cream is. Esters come in a variety of 'weights' from very light to very rich. If you want to create a rich luxurious night cream choose an ester from the heavy end of the scale such as Aprilose. If you want to create a very light 'invisible' day cream then choose a very light ester such as Propanediol Caprylate.

Esters can also determine the play time of the cream. Consumers might want a day cream that is fast absorbing and so would want a cream with a short play time (the amount of time the cream has to be massaged into the skin). For a luxurious night cream a longer play time might be preferred to increase the sensorial experience of massaging the cream into the skin.

Esters can also help determine the after feel of the cream - i.e how the skin feels after the cream has absorbed into the skin.

Certain esters can leave a soft powdery after feel (like how the skin feels after applying talc), others can leave a slight oily residue – preferable for night creams when the customer wants to feel they have a rich cream on their skin.

How to Use Esters

Esters are direct replacements for oils. If your cream contains say 15% plant oils then you can replace any amount of plant oil with an appropriate ester or blend of esters. There's no hard and fast rule about proportions of oils to esters but generally I like to use a 50-50 blend so I would reduce the plant oils down to 7.5% and add 7.5% esters. The choice of esters being determined by the skin feel I was hoping to achieve.

To keep things simple (until you become more familiar with the properties of different esters) I recommend you experiment by using one of the most popular and most commonly used esters - C12-15 Alkyl Benzoate. C12-15 Alkyl Benzoate is a light to medium weight ester which provides a light conditioning and silky after touch to the skin.

So in our standard formulation I would reduce the Almond Oil by 4% and the Hazelnut by 2% as I want to keep the extra emolliency of the Shea Butter in our recipe. I'll adjust the reduction of the Almond and Hazelnut Oils by adding 6% C12-15 Alkyl Benzoate

Our original formulation

Water Phase
Water	79.70%	797g
Xanthan	0.50%	5g
	80.20%	802g
Oil Phase
Sweet Almond Oil	9.00%	9.00g
Hazelnut Oil	4.00%	40g
Shea Butter	2.00%	20g
Emulsifying Wax	4.00%	40g
Cetyl Alcohol	0.8%%	8g
	19.20%	192g
	100.00%	1000g

Is adjusted to incorporate the esters and becomes:

Water Phase
Water	79.70%	797g
Xanthan	0.50%	5g
	80.20%	802g
Oil Phase
Sweet Almond Oil	5.00%	9.00g
Hazelnut Oil	2.00%	40g
Shea Butter	2.00%	20g
C12-15 Alkyl Benzoate	6.00%	70g
Emulsifying Wax	4.00%	40g
Cetyl Alcohol	0.8%%	8g
	19.20%	192g
	100.00%	1000g

With these adjustments the final product would have more slip, feel more elegant, less greasy, should absorb more easily, and reduce whitening (though it won't be eliminated completely).